Sucrose Synthase Activity Research Articles

Possible Roles of Carbohydrate Management and Cytokinin in the Process of Defoliation-Regrowth Cycles in Rice.

Defoliation is an inevitable abiotic stress for forage and turf grasses because harvesting, grazing, and mowing are general processes for their production and management. Vegetative regrowth occurs upon defoliation, a crucial trait determining the productivity and persistence of these grasses. However, the information about the molecular regulation of this trait is limited because it is still challenging to perform molecular analyses in forage and turf grasses. Here, we used rice as a model to investigate vegetative regrowth upon defoliation at physiological and molecular levels. This study analyzed stubble and regrown leaves following periodic defoliation using two rice varieties with contrasting regrowth vigor. Vigorous regrowth was associated with maintained chlorophyll content and photosystem II performance; a restricted and promoted mRNA accumulation of sucrose synthase (SUS) I and III subfamilies, respectively; and reduced enzymatic activity of SUS. These results suggest that critical factors affecting vegetative regrowth upon defoliation are de novo carbohydrate synthesis by newly emerged leaves and proper carbohydrate management in leaves and stubble. Physiological and genetic analyses have demonstrated that the reduced sensitivity to and inhibited biosynthesis of cytokinin enhance regrowth vigor. Proper regulation of these metabolic and hormonal pathways identified in this study can lead to the development of new grass varieties with enhanced regrowth vigor following defoliation.

Comparative metabolome profiling of two contrasting wheat cultivars in late-season water deficit

Abiotic stresses, including water deficit, cause myriad changes in plant metabolism. Metabolomics is a powerful tool for understanding plant resistance to such stresses. Therefore, this research was conducted to evaluate the effects of after anthesis water deficit (WD: from anthesis to maturity), i.e., maintaining moisture at field capacity (well-watered: WW) and 50% field capacity, on metabolome profiling (amino acids, hormones, nucleotides, soluble and insoluble sugars, sugar alcohols, and enzymes) in grains of two contrasting wheat cultivars grown in a greenhouse at Razi University as a factorial experiment. Based on the results, WD decreased grain yield (57%), 1000 grain weight (50%), and grain plant-1 (9%) in the sensitive cultivar (SC), while it had no significant effect on the tolerant cultivar (TC). In WW, the concentration of IAA, glucose, and fructose, as well as the activity of three invertase isoforms (vacuolic, cytosolic, and cell wall bound), were significantly higher at 10 days after anthesis compared to 17 and 31 days. In WD, these traits were significantly reduced in SC. ABA and sucrose concentration and sucrose synthase activity were significantly higher 17 days after anthesis than 10 days after anthesis. WD. In contrast to ABA, sucrose concentration decreased significantly in growing grains of SC in WD. The ATP/ADP ratio, inositol, glycerol and erythritol contents of TC were significantly higher in WD than in SC. Among the different amino acids, asparagine, glutamine and lysine were the highest, while ACC and methionine were the lowest. Contrary to SC, WD significantly increased the sum of the amino acid concentrations determined in the grains of TC, i.e. asparagine (22%), aspartic acid (48%), glycine (48%), ACC (79%) and valine (133%). These findings could help us to understand the resistance mechanisms to late season water deficit, which can increase sink strength (sink size and sink activity) and achieve higher yield quantity and quality in wheat.

Wheat response to winter night warming based on physiological and transcriptome analyses

Global warming is primarily characterized by asymmetric temperature increases, with higher temperature rises in winter/spring and at night compared to summer/autumn and daytime. We investigated the impact of winter night warming on wheat leaves using the spring wheat cultivar Yangmai 18 and the semi-winter wheat cultivar Yannong 19 during the 2020–2021 growing season. This study aimed to examine the effect of winter night warming on the top expanded leaf of wheat plants. The results showed that the night mean temperature in the treatment group increased by 1.27°C compared to the ambient temperature and winter night warming increased the yield of both wheat cultivars, the activities of sucrose synthase and sucrose phosphate synthase after anthesis, and the biosynthesis of sucrose and soluble sugars. The differentially expressed genes were identified using P-value<0.05 and fold change>2, and subjected to Gene Ontology annotation and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses. The genes differentially expressed in wheat leaves treated with night warming were primarily associated with starch and sucrose metabolism, amino acid biosynthesis, carbon metabolism, plant hormone signal transduction, and amino sugar and nucleotide sugar metabolism. Comparison between groups identified 14 differentially expressed genes related to temperature. These results highlight the effects of winter night warming on wheat development from various perspectives. Our results provide new insights into the molecular mechanisms of the wheat response to winter night warming and the candidate genes involved in this process.

Potassium attenuates drought damage by regulating sucrose metabolism and gene expression in sesame leaf

Drought has been considered the most restrictive environmental constraint on agricultural production worldwide. Photosynthetic carbohydrate metabolism is a critical biochemical process connected with crop production and quality traits. A pot experiment was carried out under four potassium (K) rates (0, 0.75, 1.5 and 2.25 g pot−1 of K, respectively) and two water regimes to investigate the role of K in activating defense mechanisms on sucrose metabolism against drought damage in sesame. The soil moisture contents are 75 ± 5% (well-watered, WW) and 45 ± 5% (drought stress, DS) of field capacity respectively. The results showed that DS plants without K application have lower activities of ribulose-1,5-bisphosphate carboxylase (Rubisco), sucrose phosphate synthase (SPS), soluble acid invertase (SAI), and chlorophyll content and higher activity of sucrose synthase (SuSy), which resulted in declined synthesis and distribution of photosynthetic products to reproductive organs. Under drought, there was a significant positive correlation between leaf sucrose metabolizing enzymes and sucrose content. Plants subjected to drought stress increased the concentrations of soluble sugar and sucrose to produce osmo-protectants and energy sources for plants acclimating to stress but decreased starch content. Conversely, K application enhanced the carbohydrate metabolism, biomass accumulation and partitioning, thereby contributing to higher seed oil and protein yield (28.8%–43.4% and 27.5%–40.7%) as compared to K-deficiency plants. The positive impacts of K application enhanced as increasing K rates, and it was more pronounced in drought conditions. Furthermore, K application upregulated the gene expression of SiMYB57, SiMYB155, SiMYB176 and SiMYB192 while downregulated SiMYB108 and SiMYB171 in drought conditions, which may help to alleviate drought susceptibility. Conclusively, our study illustrated that the enhanced photo-assimilation and translocation process caused by the changes in sucrose metabolism activities under K application as well as regulation of MYB gene expression contributes towards drought resistance of sesame.

Drought decreases cotton fiber strength by altering sucrose flow route.

The potential mechanisms by which drought restricts cotton fiber cell wall synthesis and fiber strength formation are still not fully understood. Herein, drought experiments were conducted using two upland cotton cultivars of Dexiamian 1 (drought-tolerant) and Yuzaomian 9110 (drought-sensitive). Results showed that drought notably reduced sucrose efflux from cottonseed coats to fibers by down-regulating the expression of GhSWEET10 and GhSWEET15 in outer cottonseed coats, leading to promoted sucrose accumulation in cottonseed coats but decreased sucrose accumulation in fibers. Within cotton fibers, drought restricted the hydrolysis from sucrose to UDPG by suppressing sucrose synthase activity, and drought favored the conversion of UDPG to β-1, 3-glucan rather than cellulose by up-regulating GhCALS5. Hence, cellulose content was reduced, which was the main reason for the decreased fiber strength under drought. Moreover, drought promoted lignin synthesis by up-regulating the expression of Gh4CL4, GhPAL9, GhCCR5, GhCAD11, and GhOMT6, which partly offset the negative influence of reduced cellulose content on fiber strength. Compared with Yuzaomian 9110, the drought-tolerance of Dexiamian 1 was evidenced in the following ways: (1) slighter blocked sucrose flow from seedcoat to fiber, (2) less β-1, 3-glucan accumulation, and (3) more lignin biosynthesis under drought. Overall, this study provides new insights into the mechanism of drought impacting cotton fiber strength formation.

Unveiling the mechanism of source-sink rebalancing in cucumber-pumpkin heterografts: the buffering roles of rootstock cotyledon.

Grafting onto pumpkin rootstock is widely applied in cucumber production to improve growth and yield, as well as to overcome soil-borne diseases and enhance resistance to abiotic stresses. In this study, we constructed the cucumber-pumpkin heterografts with the one-cotyledon grafting method, and examined the effects of heterografting on biomass allocation and sugar partitioning, with cucumber and pumpkin self-grafts used as control. Compared with cucumber self-grafts, heterografting onto pumpkin rootstock promoted photosynthesis in cucumber scion, and led to higher sucrose contents in the 1st true leaf (source) and newly emerged leaf (sink). Thereby, the scion part of heterografts accumulated more biomass than cucumber self-grafts. In contrast, when compared to pumpkin self-grafts, grafting with cucumber scion reduced root vigor and biomass but promoted cotyledon growth in pumpkin rootstock. The roots (sink) of heterografts contained less sucrose and hexoses, and showed reduced sucrose synthase (SuSy) and hexokinase (HXK) activities. However, the rootstock cotyledon (source) contained more sucrose and starch, and showed higher activities of HXK, cell-wall invertase (CWIN), and enzymes for starch synthesis and degradation. Furthermore, removal or shade of rootstock cotyledon led to reduced growth of root and scion. Silencing of CmoMEX1a gene in rootstock cotyledon inhibited maltose export and reduced root growth of heterografts. These results indicated that rootstock cotyledon, especially its starch content, played a buffering role in the growth regulation of cucumber-pumpkin heterografts. Taken together, our results provided a major contribution to our understanding of source-sink sugar partitioning and scion-rootstock growth balancing in cucumber-pumpkin heterografts.

Rice husk ash based growing media impact on cucumber and melon growth and quality

Rice husk, an agricultural waste from the rice industry, can cause serious environmental pollution if not properly managed. However, rice husk ash (RHA) has been found to have many positive properties, making it a potential replacement for non-renewable peat in soilless planting. Thus, this study investigated the impact of a RHA composite substrate on the growth, photosynthetic parameters, and fruit quality of cucumber (Yuyi longxiang variety) and melon (Yutian yangjiaomi variety). The RHA, peat, vermiculite, and perlite were blended in varying proportions, with the conventional seedling substrate (peat:vermiculite:perlite = 1:1:1 volume ratio) serving as the control (CK). All plants were cultivated in barrels filled with 10L of the mixed substrates. The results from this study found that RHA 40 (RHA:peat:vermiculite:perlite = 4:4:1:1 volume ratio) significantly enhanced substrate ventilation and positively influenced the stem diameter, root activity, seedling index, chlorophyll content, net photosynthetic rate (Pn), stomatal conductance (Gs), and transpiration rate (Tr) of cucumber and melon plants. Additionally, plant planted using RHA 40, the individual fruit weight of cucumber and melon found to increase by 34.62% and 21.67%, respectively, as compared to the control. Aside from that, both cucumber and melon fruits had significantly higher sucrose, total soluble sugar, vitamin C, and soluble protein levels. This subsequently improved the activity of sucrose synthase and sucrose phosphate synthase in both cucumber and melon. In conclusion, the RHA 40 found to best promote cucumber and melon plant growth, increase plant leaf photosynthesis, and improve cucumber and melon fruit quality, making it a suitable substrate formula for cucumber and melon cultivation in place of peat.

Sucrose, cell wall, and polyamine metabolisms involve in preserving postharvest quality of ‘Zaosu’ pear fruit by L-glutamate treatment

‘Zaosu’ pear fruit is prone to yellowing of the surface and softening of the flesh after harvest. This work was performed to assess the influences of L-glutamate treatment on the quality of ‘Zaosu’ pears and elucidate the underlying mechanisms involved. Results demonstrated that L-glutamate immersion reduced ethylene release, respiratory intensity, weight loss, brightness (L*), redness (a*), yellowness (b*), and total coloration difference (ΔE); enhanced ascorbic acid, soluble solids, and soluble sugar contents; maintained chlorophyll content and flesh firmness of pears. L-glutamate also restrained the activities of neutral invertase and acid invertase, while enhancing sucrose phosphate synthetase and sucrose synthase activities to facilitate sucrose accumulation. The transcriptions of PbSGR1, PbSGR2, PbCHL, PbPPH, PbRCCR, and PbNYC were suppressed by L-glutamate, resulting in a deceleration of chlorophyll degradation. L-glutamate concurrently suppressed the transcription levels and enzymatic activities of polygalacturonases, pectin methylesterases, cellulase, and β-glucosidase. It restrained polygalacturonic acid trans-eliminase and pectin methyl-trans-eliminase activities as well as inhibited the transcription levels of PbPL and Pbβ-gal. Moreover, the gene transcriptions and enzymatic activities of arginine decarboxylase, ornithine decarboxylase, S-adenosine methionine decarboxylase, glutamate decarboxylase, γ-aminobutyric acid transaminase, glutamine synthetase along with the PbSPDS transcription was promoted by L-glutamate. L-glutamate also resulted in the down-regulation of PbPAO, PbDAO, PbSSADH, PbGDH, and PbGOGAT transcription levels, while enhancing γ-aminobutyric acid, glutamate, and pyruvate acid contents in pears. These findings suggest that L-glutamate immersion can effectively maintain the storage quality of ‘Zaosu’ pears via modulating key enzyme activities and gene transcriptions involved in sucrose, chlorophyll, cell wall, and polyamine metabolism.

Beneficial endophytic fungi improve the yield and quality of Salvia miltiorrhiza by performing different ecological functions.

Endophytic fungi can enhance the growth and synthesis of secondary metabolites in medicinal plants. Salvia miltiorrhiza Bunge is frequently employed for treating cardiovascular and cerebrovascular ailments, with the primary bioactive components being salvianolic acid and tanshinone. However, their levels in cultivated S. miltiorrhiza are inferior to that of the wild herbs, so the production of high-quality medicinal herbs is sharply declining. Consequently, the utilization of beneficial endophytic fungi to improve the yield and quality of S. miltiorrhiza holds great significance for the cultivation of medicinal plants. In this study, nine non-pathogenic, endophytic fungal strains were introduced into sterile S. miltiorrhiza seedlings and cultivated both in vitro and in situ (the greenhouse). The effects of these strains on the growth indices, C and N metabolism, antioxidant activity, photosynthesis, and content of bioactive ingredients in S. miltiorrhiza were then evaluated. The results showed that the different genera, species, or strains of endophytic fungi regulated the growth and metabolism of S. miltiorrhiza in unique ways. These endophytic fungi primarily exerted their growth-promoting effects by increasing the net photosynthetic rate, intercellular CO2 concentration, and the activities of sucrose synthase, sucrose phosphate synthase, nitrate reductase, and glutamine synthetase. They also enhanced the adaptability and resistance to environmental stresses by improving the synthesis of osmoregulatory compounds and the activity of antioxidant enzymes. However, their regulatory effects on the growth and development of S. miltiorrhiza were affected by environmental changes. Moreover, the strains that significantly promoted the synthesis and accumulation of phenolic acids inhibited the accumulation of tanshinones components, and vice versa. The endophytic fungal strains Penicillium meloforme DS8, Berkeleyomyces basicola DS10, and Acremonium sclerotigenum DS12 enhanced the bioaccumulation of tanshinones. Fusarium solani DS16 elevated the rosmarinic acid content and yields in S. miltiorrhiza. The strain Penicillium javanicum DS5 improved the contents of dihydrotanshinone, salvianolic acid B, and rosmarinic acid. The strains P. meloforme DS8 and B. basicola DS10 improved resistance. Various endophytic fungi affected the quality and yield of S. miltiorrhiza by regulating different physiological and metabolic pathways. This study also provides a novel and effective method to maximize the effects of beneficial endophytic fungi by selecting specific strains to design microbial communities based on the different ecological functions of endophytic fungi under varying environments and for specific production goals.

Bioaccumulation of Microcystin-LR and Induced Physio-Biochemical Changes in Rice (Oryza sativa L.) at Vegetative Stage under Hydroponic Culture Conditions.

Irrigation with water containing a variety of microcystins (MCs) may pose a potential threat to the normal growth of agricultural plants. To investigate the phytotoxicity of MC-LR at environmental concentrations on rice (Oryza sativa L.), the characteristics of uptake and accumulation in plant tissues, as well as a series of key physio-biochemical process changes in leaves of rice seedlings, were measured at concentrations of 0.10, 1.0, 10.0, and 50.0 μg·L-1 in hydroponic nutrient solutions for 7, 15, 20, and 34 days. Results showed that MC-LR could be detected in rice leaves and roots in exposure groups; however, a significant accumulation trend of MC-LR in plants (BCF > 1) was only found in the 0.10 μg·L-1 group. The time-course study revealed a biphasic response of O2•- levels in rice leaves to the exposure of MC-LR, which could be attributed to the combined effects of the antioxidant system and detoxification reaction in rice. Exposure to 1.0-50.0 μg·L-1 MC-LR resulted in significant depletion of GSH and MDA contents in rice leaves at later exposure times (15-34 days). Low MC-LR concentrations promoted nitric oxide synthase (NOS) activity, whereas high concentrations inhibited NOS activity during the later exposure times. The reduced sucrose synthase (SS) activities in rice exposed to MC-LR for 34 days indicated a decrease in the carbon accumulation ability of plants, and therefore may be directly related to the inhibition of plant growth under MC exposure. These findings indicate that the normal physiological status would be disrupted in terrestrial plants, even under exposure to low concentrations of MC-LR.

Exogenous abscisic acid (ABA) improves the filling process of maize grains at different ear positions by promoting starch accumulation and regulating hormone levels under high planting density

BackgroundHigher planting densities typically cause a decline in grain weight, limiting the potential for high maize yield. Additionally, variations in grain filling occur at different positions within the maize ear. Abscisic acid (ABA) is important for grain filling and regulates grain weight. However, the effects of exogenous ABA on the filling process of maize grains at different ear positions under high planting density are poorly understood. In this study, two summer maize hybrids (DengHai605 (DH605) and ZhengDan958 (ZD958)) commonly grown in China were used to examine the effects of ABA application during the flowering stage on grain filling properties, starch accumulation, starch biosynthesis associated enzyme activities, and hormone levels of maize grain (including inferior grain (IG) and superior grain (SG)) under high planting density.ResultsOur results showed that exogenous ABA significantly increased maize yield, primarily owing to a higher grain weight resulting from an accelerated grain filling rate relative to the control. There was no significant difference in yield between DH605 and ZD958 in the control and ABA treatments. Moreover, applying ABA promoted starch accumulation by raising the activities of sucrose synthase, ADP-glucose pyrophosphorylase, granule-bound starch synthases, soluble starch synthase, and starch branching enzyme in grains. It also increased the levels of zeatin riboside, indole-3-acetic acid, and ABA and decreased the level of gibberellin in grains, resulting in more efficient grain filling. Notably, IG exhibited a less efficient filling process compared to SG, probably due to lower starch biosynthesis associated enzyme activities and an imbalance in hormone contents. Nevertheless, IG displayed greater sensitivity to exogenous ABA than SG, suggesting that appropriate cultural measures to improve IG filling may be a viable strategy to further increase maize yield.ConclusionsAccording to our results, spraying exogenous ABA could effectively improve grain filling properties, accelerate starch accumulation by increasing relevant enzyme activities, and regulate hormone levels in grains, resulting in higher grain weight and yield of maize under high planting density. Our findings offer more evidence for using exogenous hormones to improve maize yield under high planting density.

Overexpression of ZmSUS1 increased drought resistance of maize (Zea mays L.) by regulating sucrose metabolism and soluble sugar content.

ZmSUS1 improved drought tolerance of maize by regulating sucrose metabolism and increasing soluble sugar content, and endowing transgenic maize with higher relative water content and photosynthesis levels. Sucrose synthase (SUS), a key enzyme of sugar metabolism, plays an important role in the regulation of carbon partitioning in plant, and affects important agronomic traits and abiotic responses to adversity. However, the function of ZmSUS1 in plant drought tolerance is still unknown. In this study, the expression patterns of ZmSUS1 in different tissues and under drought stress were analyzed in maize (Zea mays L.). It was found that ZmSUS1 was highly expressed during kernel development but also in leaves and roots of maize, and ZmSUS1 was induced by drought stress. Homozygous transgenic maize lines overexpressing ZmSUS1 increased the content and activity of SUS under drought stress and exhibited higher relative water content, proline and abscisic acid content in leaves. Specifically, the net photosynthetic rate and the soluble sugar contents including sucrose, glucose, fructose and SUS decomposition products including UDP-glucose (UDP-G) and ADP-glucose (ADP-G) in transgenic plants were significantly improved after drought stress. RNA-seq analysis showed that overexpressing of ZmSUS1 mainly affected the expression level of carbon metabolism-related genes. Especially the expression level of sucrose metabolism-related genes including sucrose phosphatase gene (SPP), sucrose phosphate synthase gene (SPS) and invertase gene (INV) were significantly up-regulated in transgenic maize. Overall, these results suggested that ZmSUS1 improved drought tolerance by regulating sucrose metabolism and increasing the soluble sugar content, and endowing transgenic maize with higher relative water content and photosynthesis levels, which can serve as a new gene candidate for cultivating drought-resistant maize varieties.

Physiological and biochemical processes underlying the differential sucrose yield and biomass production in sugarcane varieties

Physiological and biochemical processes underlying the differential sucrose yield and biomass production in sugarcane varieties

Calcium signal regulated carbohydrate metabolism in wheat seedlings under salinity stress.

This study aimed to explore the mechanism by which calcium (Ca) signal regulated carbohydrate metabolism and exogenous Ca alleviated salinity toxicity. Wheat seedlings were treated with sodium chloride (NaCl, 150mM) alone or combined with 500μM calcium chloride (CaCl2), lanthanum chloride (LaCl3) and/or ethylene glycol tetraacetic acid (EGTA) to primarily analyse carbohydrate starch and sucrose metabolism, as well as Ca signaling components. Treatment with NaCl, EGTA, or LaCl3 alone retarded wheat-seedling growth and decreased starch content accompanied by weakened ribulose-1,5-bisphosphate carboxylation/oxygenase (Rubisco) and Rubisco activase activities, as well as enhanced glyceraldehyde-3-phosphate dehydrogenase, phosphoglycerate kinase, alpha-amylase, and beta-amylase activities. However, it increased the sucrose level, up-regulated the sucrose phosphate synthase (SPS) and sucrose synthase (SuSy) activities and TaSPS and TaSuSy expression together, but down-regulated the acid invertase (SA-Inv) and alkaline/neutral invertase (A/N-Inv) activities and TaSA-Inv and TaA/N-Inv expression. Except for unchanged A/N-Inv activities and TaA/N-Inv expression, adding CaCl2 effectively blocked the sodium salt-induced changes of these parameters, which was partially eliminated by EGTA or LaCl3 presence. Furthermore, NaCl treatment also significantly inhibited Ca-dependent protein kinases and Ca2+-ATPase activities and their gene expression in wheat leaves, which was effectively relieved by adding CaCl2. Taken together, CaCl2 application effectively alleviated the sodium salt-induced retardation of wheat-seedling growth by enhancing starch anabolism and sucrose catabolism, and intracellular Ca signal regulated the enzyme activities and gene expression of starch and sucrose metabolism in the leaves of sodium salt-stressed wheat seedlings.

Source-sink coordinated peanut cultivar increases yield and kernel protein content through enhancing photosynthetic characteristics and regulating carbon and nitrogen metabolisms

The grain yield of crops is determined by the synergistic interaction between source activity and sink capacity. However, source-sink interactions are far from being fully understood of peanut. Therefore, a 2-year field study (2018–2019) was conducted to compare differences in photosynthetic characteristics, carbon and nitrogen metabolism, and yield and quality of different source–sink peanut varieties. Four representative source–sink types were examined: JH5 (source–sink coordination type), SH9 (sufficient source–large sink type), ZH24 (sufficient source–few sink type), and HY36 (large source–few sink type). The results showed that the photosynthetic potential of HY36 was higher than that of the other varieties after flowering because of a large source (leaves), whereas the chlorophyll content and net photosynthetic rate of HY36 were significantly lower than those of JH5 and ZH24. Proportions of dry matter transferred to pods were significantly different among four source–sink peanut varieties. From 50 days after flowering, the dry matter distribution ratio of pods exceeded that of stems and leaves in JH5, significantly earlier than other varieties, which prolong the duration of pod-filling period, followed by SH9 and ZH24. The activities of nitrate reductase, glutamine synthetase, glutamate dehydrogenase, and glutamate synthase in JH5 were the highest among the varieties, and thus, the highest protein content was also in JH5. The activities of sucrose synthase and sucrose phosphate synthase in ZH24 were significantly higher than those in HY36. The highest oil content was also in ZH24. Among pod sink characteristics and yield, SH9 had the longest flowering period and the highest gynophore formation rate but the lowest pod-bearing rate, and the effective proportion and pod fullness were also lower than those of other varieties. The highest pod rate was in ZH24. The effective proportion and pod fullness of JH5 were higher than those of the other varieties, and its yield was also the highest, followed by SH9 and ZH24, with the lowest yield in HY36. The obtained results indicate that the source–sink coordinated variety had high Pn and chlorophyll content in the late growth stage, a long functional period of leaves, and a high proportion of assimilates transported to pods, thus promoting effective proportions and pod fullness to improve peanut yield and protein content, suggesting that different cultivation and management measures should select for different peanut varieties to best coordinate the relationship between the source and sink.

Exogenous application of ALA enhanced sugar, acid and aroma qualities in tomato fruit.

The content and proportion of sugars and acids in tomato fruit directly affect its flavor quality. Previous studies have shown that 5-aminolevulinic acid (ALA) could promote fruit ripening and improve its aroma quality. In order to explore the effect of ALA on sugar and acid quality during tomato fruit development, 0, 100, and 200 mg L-1 ALA solutions were sprayed on the fruit surface 10 days after pollination of the fourth inflorescence, and the regulation of ALA on sugar, acid metabolism and flavor quality of tomato fruit was analyzed. The results showed that ALA treatment could enhance the activities of acid invertase (AI), neutral invertase (NI), and sucrose synthase (SS), reduce the activity of sucrose phosphate synthase (SPS), up-regulate the expression of SlAI, SlNI and SlSS, change the composition and content of sugar in tomato fruit at three stages, significantly increase the content of sugars in fruit, and promote the accumulation of sugars into flesh. Secondly, ALA treatments increased the activities of phosphoenolpyruvate carboxykinase (PEPC), malic enzyme (ME), and citrate synthase (CS), up-regulated the expression of SlPPC2, SlME1, and SlCS, and reduced the citric acid content at maturity stage, thereby reducing the total organic acid content. In addition, ALA could also increase the number and mass fraction of volatile components in mature tomato fruits. These results indicated that exogenous application of ALA during tomato fruit development could promote the formation of fruit aroma quality and were also conducive to the formation of fruit sugar and acid quality.

Phosphorus-induced improvement of photosynthate synthesis and transport in the leaf subtending to cotton boll provided sufficient sucrose for fiber thickening during the crucial period and improved fiber bundle strength

ContextCotton fiber is an important natural textile raw material, and its quality directly affects spinning performance. Phosphorus (P) deficiency reduces fiber quality, particularly fiber strength. Fiber strength formation relies on sucrose supplied by the leaf subtending to cotton boll (LSCB), and low P may affect it by regulating sucrose supply and utilization in LSCB and fiber. ObjectiveOur study aimed to investigate how P regulates the formation of fiber bundle strength through essential carbohydrate metabolic pathways. MethodsA three-year experiment on Lu 54 (low-P sensitive) and Yuzaomian 9110 (low-P tolerant) was carried out to study the influence of P on sucrose synthesis and export in LSCB, sucrose absorption and utilization in fiber under 0 (Deficient P), 100 (Critical P), and 200 (Excessive P) kg P2O5 ha−1 in soil with 16.9 mg kg−1 available P. ResultsP application significantly increased fiber bundle strength (8.9 %−14.6 %), primarily attributed to the enhanced sucrose supply and utilization in LSCB and fiber during the crucial period for fiber bundle strength formation (17–24 days post anthesis). During this period, P application promoted the sucrose synthesis in LSCB by improving the net photosynthetic rate (9.0 %−16.8 %), and sucrose phosphate synthase (6.3 %−12.4 %) and sucrose synthase (10.0 %−17.4 %) activities. Concomitantly, P application up-regulated the expressions of sucrose transporter genes in LSCB and fiber, promoting sucrose transport and increasing the sucrose content (28.1 %−54.0 %) in fiber. Furthermore, P application markedly enhanced the sucrose utilization in fiber by increasing sucrose synthase (9.7 %−19.2 %) and invertase (14.0 %−35.7 %) activities, improving cellulose content (6.7 %−11.5 %) and fiber bundle strength. Lu 54 exhibited a greater sensitivity to P in the carbohydrate metabolism of LSCB and fiber than Yuzaomian 9110, making its cellulose content and fiber bundle strength increase more. Incremental effects of unit P on the above measurements attenuated markedly with P rates. The critical P content in LSCB (LPC) required for effective fiber bundle strength formation was 0.40 % for Lu 54 versus 0.36 % for Yuzaomain 9110, on the basis of the content of sucrose (the key substrate) in LSCB and fiber. ConclusionP application increased cotton fiber bundle strength mainly by enhancing sucrose synthesis in LSCB, sucrose transport between LSCB and fiber, and sucrose utilization in fiber during the crucial period. ImplicationThis report revealed the crucial carbohydrate metabolic path by which P regulated the fiber bundle strength formation and quantified its LPC demand during the crucial period, providing theoretical support for P diagnosis and regulation in cotton cultivation.

An integrated physiology and proteomics analysis reveals the response of wheat grain to low temperature stress during booting

The low temperature (LT) in spring has become one of the principal abiotic stresses that restrict the growth and development of wheat. Diverse analyses were performed to investigate the mechanism underlying the response of wheat grain development to LT stress during booting. These included morphological observation, measurements of starch synthase activity, and determination of amylose and amylopectin content of wheat grain after exposure to treatment with LT during booting. Additionally, proteomic analysis was performed using tandem mass tags (TMT). The results showed that the plumpness of wheat grains decreased after LT stress. Moreover, the activities of sucrose synthase (SuS, EC 2.4.1.13) and ADP-glucose pyrophosphorylase (AGPase, EC 2.7.7.27) exhibited a significant reduction, leading to a significant reduction in the contents of amylose and amylopectin. A total of 509 differentially expressed proteins (DEPs) were identified by proteomics analysis. The GO enrichment analysis showed that the protein difference multiple in the nutritional repository activity was the largest among the molecular functions, and the up-regulated seed storage protein (SSP) played an active role in the response of grains to LT stress and subsequent damage. The KEGG enrichment analysis showed that LT stress reduced the expression of DEPs such as sucrose phosphate synthase (SPS), glucose-1-phosphate adenosine transferase (glgC), and β-fructofuranosidase (FFase) in sucrose and starch metabolic pathways, thus affecting the synthesis of grain starch. In addition, many heat shock proteins (HSPs) were found in the protein processing in the endoplasmic reticulum pathways, which can resist some damage caused by LT stress. These findings provide a new theoretical foundation for elucidating the underlying mechanism governing wheat yield development after exposure to LT stress in spring.

Transcriptomic and metabolomic analysis of changes in grain weight potential induced by water stress in wheat

The sink strength of developing ovaries in wheat determines the grain weight potential. The period from booting to the grain setting stage is critical for ovary growth and development and potential sink capacity determination. However, the underlying regulatory mechanism during this period by which the wheat plant balances and coordinates the floret number and ovary/grain weight under water stress has not been clarified. Therefore, we designed two irrigation treatments of W0 (no seasonal irrigation) and W1 (additional 75 mm of irrigation at the jointing stage) and analyzed the responses of the ovary/grain weight to water stress at the phenotypic, metabolomic, and transcriptomic levels. The results showed that the W0 irrigation treatment reduced the soil water content, plant height, and green area of the flag leaf, thus reducing grain number, especially for the inferior grains. However, it improved the grain weight of the superior and inferior grains as well as average grain weight at maturity, while the average ovary/grain weight and volume during –3 to 10 days after anthesis (DAA) also increased. Transcriptomic analysis indicated that the genes involved in both sucrose metabolism and phytohormone signal transduction were prominently accelerated by the W0 treatment, accompanied by greater enzymatic activities of soluble acid invertase (SAI) and sucrose synthase (Sus) and elevated abscisic acid (ABA) and indole-3-acetic acid (IAA) levels. Thus, the sucrose content decreased, while the glucose and fructose contents increased. In addition, several TaTPP genes (especially TaTPP-6) were down-regulated and the IAA biosynthesis genes TaTAR1 and TaTAR2 were up-regulated under the W0 treatment before anthesis, which further increased the IAA level. Collectively, water stress reduced the growth of vegetative organs and eliminated most of the inferior grains, but increased the ABA and IAA levels of the surviving ovaries/grains, promoting the enzymatic activity of Sus and degrading sucrose into glucose and fructose. As a result, the strong sucrose utilization ability, the enhanced enzymatic activity of SAI and the ABA- and IAA-mediated signaling jointly increased the weight and volume of the surviving ovaries/grains, and ultimately achieved the trade-off between ovary/grain weight and number in wheat under water stress.

Waterlogging restricted cotton fiber elongation by reducing osmolyte accumulation and cell wall biosynthesis

Waterlogging severely threatens the formation of cotton fiber quality, especially the length. However, the underlying mechanism is still incompletely understood. Here, the experiment (control: soil relative water content at (75 ± 5)%; treatment: waterlogging for 6 days) was conducted during the flowering and boll forming stage using two upland cotton cultivars (Dexiamian 1 and Yuzaomian 9110) to investigate the effects of waterlogging on fiber development from both transcriptomic and physiological levels. The transcriptome analysis of 10 days post anthesis cotton fiber showed that waterlogging significantly regulated the expression of genes associated with fiber elongation events including osmotic solutes accumulation, fiber cell wall biosynthesis, and cell wall remodeling and loosening. Waterlogging decreased the sucrose input into cotton fiber, resulting in reduced sucrose and hexose contents. Under waterlogging, the accumulation of malate and K+ in both cultivars was reduced by decreasing phosphoenolpyruvate carboxylase (PEPC) activity and potassium transporter genes (GhPOT) expression, respectively. Thus, the total concentration of osmolytes was reduced, which dampened cotton fiber elongation. Due to reduced sucrose synthase activity and uridine diphosphate glucose content, the cellulose biosynthesis was limited, leading to decreased fiber cell wall accumulation, which was adverse to fiber elongation. Besides, genes responsible for cell wall remodeling and loosening, including xyloglucan endotransglucosylase/hydrolase genes (GhXTH), α-expansin genes (GhEXPA), and pectin methylesterase genes (GhPME) were also responsive to waterlogging, but in different ways between cultivars. Overall, the shortened cotton fiber could be attributed to reduced osmolytes accumulation and cell wall biosynthesis, whilst the effects of waterlogging on cotton fiber cell wall loosening require further exploration.