Sucrose Phosphate Synthase Research Articles

An efficient triose phosphate synthesis and distribution in wheat provides tolerance to higher field temperatures.

High temperatures in the field hinder bread wheat high-yield production, mainly because of the adverse effects of heat over photosynthesis. The Yaqui Valley, the main wheat producer region in Mexico, is a zone prone to have temperatures over 30°C. The aim of this work was to test the flag leaf photosynthetic performance in 10 bread wheat genotypes grown under high temperatures in the field. The study took place during two seasons (2019-2020 and 2020-2021). In each season, control seeds were sown in December, while heat-stressed were sown in late January to subject wheat to heat stress (HS) during the grain-filling stage. HS reduced Grain yield from 20 to 58% in the first season. HS did not reduce chlorophyll content and light-dependent reactions were unaffected in any of the tested genotypes. Rubisco, chloroplast fructose 1,6-biphosphatase (FBPase), and sucrose phosphate synthase (SPS) activities were measured spectrophotometrically. Rubisco activity did not decrease under HS in any of the genotypes. FBPase activity was reduced by HS indicating that triose phosphate flux to starch synthesis was reduced, while SPS was not affected, and thus, sucrose synthesis was maintained. HS reduced aerial biomass in the 10 chosen genotypes. Genotypes SOKWB.1, SOKWB.3, and BORLAUG100 maintained their yield under HS, pointing to a potential success in their introduction in this region for breeding heat-tolerant bread wheat.

Sugar metabolism and 14-3-3 protein genes expression induced by arbuscular mycorrhizal fungi and phosphorus addition to response drought stress in Populus cathayana

Sugar, as a nutrient exchange substance between arbuscular mycorrhizal (AM) fungi and host plants, plays an important role in the abiotic stress response of mycorrhizal plants. This experiment aimed to study the effects of AM fungi and phosphorus (P) addition on the sugar metabolism and 14-3-3 gene expression of Populus cathayana under drought stress. The results showed that drought affects the process of sugar metabolism by increasing the activities of amylase and invertase, resulting in the decrease of starch content in leaves and roots and the accumulation of soluble sugars (including reducing sugar and sucrose) in roots. Under drought stress, the activity or content of sucrose synthetase, sucrose phosphate synthase, acid invertase, alkaline invertase, reducing sugar, soluble sugar, sucrose, and starch in the root showed the best mycorrhizal effect at the 100 mg P level. The expression levels of the 14-3-3 genes (PcGRF10 and PcGRF11) were significantly increased by mycorrhizal induction under drought stress. These levels were positively correlated with SS, SPS, sucrose, and starch phosphorylase in leaves, as well as with almost all sugar metabolism indicators in roots. However, they were negatively correlated with starch content in both leaves and roots. Sugar metabolism and 14-3-3 protein gene expression were induced by AM fungi and P addition in response to drought stress. The 14-3-3 genes induced by AM fungi may be involved in participating in osmotic regulation during drought stress. This study provides a new idea for the mechanism of sugar metabolism of mycorrhizal plants in arid regions.

Genome-Wide Identification of GmSPS Gene Family in Soybean and Expression Analysis in Response to Cold Stress.

Sucrose metabolism plays a critical role in development, stress response, and yield formation of plants. Sucrose phosphate synthase (SPS) is the key rate-limiting enzyme in the sucrose synthesis pathway. To date, genome-wide survey and comprehensive analysis of the SPS gene family in soybean (Glycine max) have yet to be performed. In this study, seven genes encoding SPS were identified in soybean genome. The structural characteristics, phylogenetics, tissue expression patterns, and cold stress response of these GmSPSs were investigated. A comparative phylogenetic analysis of SPS proteins in soybean, Medicago truncatula, Medicago sativa, Lotus japonicus, Arabidopsis, and rice revealed four families. GmSPSs were clustered into three families from A to C, and have undergone five segmental duplication events under purifying selection. All GmSPS genes had various expression patterns in different tissues, and family A members GmSPS13/17 were highly expressed in nodules. Remarkably, all GmSPS promoters contain multiple low-temperature-responsive elements such as potential binding sites of inducer of CBF expression 1 (ICE1), the central regulator in cold response. qRT-PCR proved that these GmSPS genes, especially GmSPS8/18, were induced by cold treatment in soybean leaves, and the expression pattern of GmICE1 under cold treatment was similar to that of GmSPS8/18. Further transient expression analysis in Nicotiana benthamiana and electrophoretic mobility shift assay (EMSA) indicated that GmSPS8 and GmSPS18 transcriptions were directly activated by GmICE1. Taken together, our findings may aid in future efforts to clarify the potential roles of GmSPS genes in response to cold stress in soybean.

Mitigation of Salt Stress in Reaumuria soongarica Seedlings by Exogenous Ca2+ and NO Compound Treatment

Soil salinization is a common abiotic stress that severely limits the growth of Reaumuria soongarica and reduces its application value. To better understand the response of R. soongarica to salt stress and the physiological mechanisms of exogenous Ca2+ and NO compound treatment in alleviating salt stress, the growth parameters, antioxidant system, carbohydrate metabolism and nitrogen compound metabolism were compared on Days 0, 1, 3, 6, 9, 15 and 30. The results showed that salt stress could significantly reduce the plant height, root length, fresh and dry weights of aboveground and underground parts, as well as the relative water content, severely inhibiting the growth of R. soongarica seedlings. After Ca2+ and NO compound treatment, these growth parameters were significantly improved, and the harm caused by stress in R. soongarica was alleviated. Regarding the antioxidant system, the Ca2+ and NO compound treatment could significantly increase the activities of SOD, CAT, APX and GR, as well as the contents of ASA and GSH, which indicated that exogenous Ca2+ and NO could eliminate the accumulated active oxygen by increasing the activities of oxidoreductases and the content of nonenzymatic antioxidant substances, thereby improving the salt tolerance of R. soongarica. Regarding carbon metabolism, after Ca2+ and NO compound treatment, the soluble sugar and sucrose contents, as well as the activities of sucrose phosphate synthase and sucrose synthase, were significantly increased, which indicated that Ca2+ and NO compound treatment could maintain higher soluble sugar and sucrose contents in R. soongarica and reduce osmotic stress caused by salt treatment. Regarding nitrogen metabolism, the Ca2+ and NO compound treatment reduced the harm of salt stress by regulating the nitrogen compound contents and nitrogen compound-related enzyme activities, including increases in the NO3− content and NR, NiR, GS, GOGAT and GDH activities and a reduction in the NO2− content. The results of this study indicate that the inhibition of the growth and development of R. soongarica by salt stress can be alleviated by regulating the antioxidant system, carbohydrate metabolism and nitrogen compound metabolism, which provides a theoretical basis for Ca2+ and NO compound treatment to improve plant salt tolerance.

Sugar composition and transcriptome analysis in developing ‘Fengtang’ plum (Prunus salicina Lindl.) reveal candidate genes regulating sugar accumulation

Sweetness is an important attribute of fruit quality, which directly affects consumers' preference for fresh fruit and is mostly determined by carbohydrate composition. ‘Fengtang’ plum (Prunus salicina Lindl.) is recognized for its high soluble sugar content, but the sugar composition and the molecular mechanisms underlying sugar overproduction are not fully understood. In this work, the sugar components were analyzed using gas chromatography-mass spectrometry combined with transcription profiles from RNA-sequencing and Quantitative Real-time PCR during fruit development. The target metabolic group showed that sucrose was the dominant sugar component in mature fruit, followed by glucose, fructose, and sorbitol. Based on the transcriptome data and qRT-PCR validation, we identified 12 key structural genes that significantly responded to corresponding component accumulation: sucrose synthase (PsSUS4), sucrose phosphate synthase (PsSPS2), neutral invertase (PsNINV1/3/4), phosphoglucomutase (PsPGM1), UTP-glucose-1-phosphate uridylyl transferase (PsUGP1/2), hexose kinase (PsHXK1/3), sugar transport protein (PsSTP1), and Sugars Will Eventually be Exported Transporter (PsSWEET4). In which PsSUS4 and PsSPS2, whose encoding proteins immediately catalyze sucrose synthesis, were selected to be silenced using the virus-induced gene silencing technology. Silencing of PsSUS4 or PsSPS2 resulted in decreased sucrose content by 27.6% and 8%, respectively, compared with the control, verifying their important roles in sucrose accumulation. Subsequently, sugar metabolism networks in this high-sugar plum were constructed with 12 key structural genes, 72 putative transcription factors, and 4 major sugar components. These results might facilitate a better understanding of the molecular mechanisms of sugar accumulation in ‘Fengtang’ plum and provide a framework for future fruit quality improvement.

Night warming from tillering to jointing increases post-anthesis flag leaf photosynthetic capacity and wheat yield

Global warming is asymmetric, with the increase in temperature at night being greater than that during the day. The objectives of this study were to assess the effects of night warming during different growth stages on the wheat grain yield, dry matter accumulation and distribution, photosynthetic characteristics, and enzymes related to sucrose metabolism. For that, field experiments with passive night warming were conducted using local spring type cultivars ‘Yangmai 18′ and ‘Sumai 188′ and semi-winter type cultivars ‘Yannong 19′ and ‘Annong 0711′ in two growing seasons in the Yangtze River Basin of China (average night time temperature increases of 1.45 °C and 1.56 °C for 2019–2020 and 2020–2021, respectively). The cultivars were exposed to night warming between four different growth stages (tillering to jointing [NWT-J], jointing to booting [NWJ-B], and booting to anthesis [NWB-A]) after 50% of plants had attained the treatment-start stage (tillering: Zadoks growth stage 21, main shoot and one tiller; jointing: Zadoks growth stage 31, the 1st node was detectable; booting: Zadoks growth stage 41, flag leaf sheath extension stage; anthesis: Zadoks growth stage 60, the beginning of pollination). Plants grown under ambient conditions were considered as the control (NN). Treatment NWT-J increased dry matter accumulation in flag leaves and spikes at anthesis and maturity, ultimately benefiting the yield, and the increase was higher in the semi-winter type cultivars. NWT-J increased not only the chlorophyll content, photosynthetic traits (net photosynthetic rate, stomatal conductance, and transpiration rate), and the activities of the maximum efficiency of PSII photochemistry under dark-adapted wheat flag leaves at the grain-filling stage (14 days after anthesis) but also the activities of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), fructose-1,6-bisphosphatase (FBPase), and glycolate oxidase (GOX), and thus improved the photosynthetic capacity of wheat flag leaves and facilitating photosynthate accumulation. NWT-J also increased sucrose-phosphate synthase activity in flag leaves at the grain-filling stage, which could improve sucrose content. Collectively, early vegetative night warming (warming during tillering-jointing) improved the photosynthetic capacity of the flag leaves during the grain-filling stage and promoted the post-anthesis accumulation of dry matter and the transfer of dry matter to the grains, which ultimately benefited the yield.

Nitrogen supply alleviates seed yield reduction by improving the morphology and carbon metabolism of pod walls in shaded rapeseed.

Shading significantly affects rapeseed yield, while reasonable nitrogen (N) application has efficiency gains. However, the functions and mechanisms of N are not fully established for shaded rapeseed plants. Therefore, we conducted a 2-year field experiment to study the effect of N on pod wall morphology and carbon metabolism of shaded rapeseed. Two varieties, three N rates (120 [N1], 240 [N2], and 360 [N3] kg hm-2 ) and two light intensities (100 and 70% light transmission) from 10 to 35 days after the end of flowering were set as experimental parameters. Shading decreased the pod wall chlorophyll content, ribulose 1,5-bisphosphate carboxylase (Rubisco) activity and glucose content at 25 and 35 days after flowering (DAF). Decreased sucrose synthase (SuSy) and sucrose phosphate synthase activity caused by shading reduced sucrose and fructose content. They are responsible for the decline in the 1000-seed weight and a 22.1-37.6% decline in seed yield. More N under shading promoted pod elongation and pigment content, improved chloroplast ultrastructure, increased Rubisco and SuSy activity at 35 DAF, thus contributing to pod wall photosynthesis and fructose and glucose levels in shaded rapeseed plants. Similar trends were observed in pod number, pod weight, and seed weight, while the greatest increase in seed/wall ratio was observed under N2 for shaded rapeseed plants. The results indicated that N can reduce the yield difference between different light conditions and balance partitioning and conversion of photoassimilates in pod wall, but avoid applying an excessive amount of nitrogen.

Effects of Extreme Root Restriction on the Nutritional and Flavor Quality, and Sucrose Metabolism of Tomato (Solanum lycopersicum L.)

Root restriction is suitable for horticultural soilless cultivation characterized by high efficiency and quality in the case of high density and low node order pinching. However, little research is available on the mechanism of root restriction improving the flavor and nutritional quality of tomatoes. We investigated the effects of Extreme Root Restriction (ERR, 750 mL/plant) on the content of metabolites, activity of enzymes, and gene expression level involving sucrose metabolism in different clusters of two tomato types. The fruit diameter and single fruit weight of common tomato at CIII were reduced by 5.6% and 14% under ERR, as a result, the fruit uniformity throughout the whole plant was improved. The ERR enhanced the accumulation of metabolites in tomato fruits, such as soluble sugars, amino acids, vitamin C, lycopene, and polyphenol, which was caused by ‘concentration effect’ that occurred with a reduction of fruit size. The activities of enzymes (SS, SPS, NI, AI) at CIII and CIV of cherry tomatoes increased by 3–4 folds under ERR. ERR enhanced accumulation of sucrose, glucose, and fructose in tomato fruits not only by modulating activities of metabolizing enzymes but also by inducing the expression of sucrose metabolism genes, including sucrose synthase genes (SS1, SS3–6) in common tomato, fructokinase genes (FKs), hexokinase genes (HKs), and sucrose phosphate synthase genes (SPSs), in cherry tomato. The above results are expected to provide a theoretical basis for root restriction cultivation techniques and practical guidance for high-quality tomato production in industrialized cultivation.

Transcriptomic Insights into the Development of Olecranon Honey Peach Fruits Using Two Different Planting Methods

The olecranon honey peach is China’s national geographic identification product because of its crisp texture and high sweetness. In recent years, new field management practices have been developed. In this study, fruits (‘SJH’) grown through new planting methods, i.e., black bags combined with bio-organic fermentation fertilizer, were compared with those (‘SBY’) grown by conventional planting methods, i.e., using a chemical fertilizer without bagging, to determine their effects on improving fruit quality. At maturity, the ‘SJH’ was significantly higher than ‘SBY’ in terms of weight, hardness, and sugar content by 14.43%, 19.55% and 9.66%, respectively. RNA sequencing (RNA-seq) technology analysis was performed on ‘SJH’ and ‘SBY’ to identify the main regulatory pathways involved in fruit development, especially focusing on cell-wall biogenesis and sugar metabolism. We identified a total of 1660 differentially expressed genes (DEGs) in ‘SJH’ and 5673 genes in ‘SBY’ throughout the development. A clustering analysis of DEGs revealed that the expression patterns of key genes involved in cell-wall biogenesis and sugar metabolism pathways in ‘SJH’ differed from those in ‘SBY’, such as cellulose synthase-like protein D (CS-LPD), sucrose-phosphate synthase (SPS) and sucrose synthase (SUS). The new cultivation technology promoted soluble sugar accumulation and cell-wall synthesis through molecular regulation, which improved the sweetness and sensory quality of the fruit. These findings contribute towards to the development of novel ideas for the better cultivation of peaches and provide a deeper investigation into the molecular mechanism of their development.

Impact of carbohydrate metabolism pathways on bearing habit of mango (Mangifera indica L.) genotypes

Heterozygosity is the major constraint in perennial fruit crop like mango for regular bearing breeding. Majority of the popular mango varieties have irregular bearing habit. Many external and internal factors affect the bearing habit of perennial fruit crops. Among internal factors, the level of carbohydrate reserves and phytohormones plays a major role on bearing habit of fruit crops like apple, citrus, mango, litchi etc., Therefore, present research work aimed to study the carbohydrate metabolism pathways in regular and irregular mango genotypes of varying origin. A total of 30 primers were designed using in silico mining of four key genes coding for citrate synthase, alcohol dehydrogenase, sucrose phosphate synthase and trehalose phosphate synthase. These genes play important role in sugar and starch metabolism in mango. Of these specific primers, 14 showed polymorphism among the genotypes studied. Gene diversity (GD), average number of alleles per locus (An), polymorphism information content (PIC) and major allele frequency (Maf) observed were 0.45, 2.14, 0.35, 0.59, respectively. Simple sequence repeats markers grouped 63.15% studied mango genotypes of regular bearers together. Further, these markers could be utilized in a greater number of genotypes for regularity.

Reducing the sink/source ratio of on-date palm plants during fruit growth has physiological and biochemical impacts on the shift in source-sink limitations.

The present study examined the impact of reducing the 'sink' on the 'source' in On-palms with a bunch number greater than eight. The capacity of leaves and fruit, as well as assimilate loading and unloading in phloem, restrict plant growth and yield. The study evaluated yield components, as well as photosynthetic and hormonal feedback, resulting from source-sink relationships. During the mid-Kimri, removing bunches from On-trees stabilized yield components and fruit size, suggesting that On-trees have a sink limitation. Bunch thinning boosted these indicators compared to normal trees with a bunch number between six and eight inclusive, indicating that On-trees had source limitations. In mid-Khalal, the treatments presented a type of source and sink limitation that is opposite to mid-Kimri. The thinning techniques addressed the source-sink limitation by adjusting the additional carbon allocation. This resulted in an increase of non-reducing sugars and starch in different organs, whereas reducing sugars decreased. These adjustments were made to reduce sucrose-phosphate synthase and sucrose synthase activity, raising invertase activity, lowering indole-3-acetic acid, zeatin, gibberellin, and abscisic acid hormone levels in fruits, as well as lowering trehalose production in organs. Levels of hormones, enzymes, and trehalose showed less variation during bunch thinning and source limitation compared to bunch removal and sink limitation. At Rutab, thinning types demonstrated the source limitation of On-trees. Bunch removal and bunch thinning by removing the source-sink limitation had the greatest effect on increasing yield components and fruit size, respectively. To improve the quality and quantity of fruit, it is important to use both thinning techniques simultaneously. © 2023 Society of Chemical Industry.

PvSPS4 is involved in regulation of root sugar balance in common bean under salt stress

Salinity is a stress factor that decreases global agricultural yield. Crops such as rice, tomato, potato, and legumes are susceptible to salt, thus this problem requires urgent attention. Disruption of carbohydrate metabolism can have negative effects on stress tolerance. Sucrose phosphate synthase (SPS) enzymes operate in a key regulatory step in sucrose synthesis. Therefore, they have a significant role in the regulation of sugar metabolism. This study focused on the function of the SPS homolog -pvSPS4- in the roots of legume crop common bean under salinity stress. We previously showed that pvSPS4 expression is root-specific and is upregulated under salt stress in a salt-tolerant common bean genotype. This upregulation was accompanied by an accumulation of sugars in the roots. In the current study, using the same genotype, we generated composite common bean plants with wild-type shoot and pvSPS4 knock-down roots. Composite plants exhibited a more sensitive phenotype under salt stress compared to control and mock plants. pvSPS4 knock-down disturbed the root glucose/sucrose ratio and balance of Ca+2, Mg+2, and K+ in both root and leaves which resulted in a reduction in photosynthetic pigments together with osmoregulation and antioxidant capability. Our results imply that pvSPS4 is an important gene for carbohydrate balance regulation under salt-stress in the common bean root tissues and sets an example for the significance of mainly disregarded roles of SPS genes in sink tissues.

Nontarget Site-Based Resistance to Fenoxaprop-P-ethyl and Candidate Genes Involved in Alopecurus japonicus

Nontarget-site resistance (NTSR) is a complex multigenic trait that is associated with the potential mechanisms of herbicide resistance which pose a serious threat to global crop protection. However, the NTSR mechanisms of Alopecurus japonicus, a malignant weed infesting wheat fields, are less characterized. In this study, we used RNA-sequencing transcriptome and enzyme activity detection to investigate the NTSR mechanisms and candidate genes involved in fenoxaprop-P-ethyl (FE) in a previously identified resistant population compared to the sensitive population of A. japonicus. Transcriptome analysis identified nine upregulated genes, which were constitutively overexpressed and upregulated by FE application in the resistant population, and the results were validated using quantitative real-time PCR. These genes including one cytochrome P450 monooxygenase (P450) gene (CYP75B4), one ATP-binding cassette (ABC) transporter gene (ABCG36), one laccase (LAC) gene (LAC15), one 9-cis-epoxycarotenoid dioxygenase (NCED) gene (NCED5), two purple acid phosphatase (PAP) genes (PAP4, PAP15), one sucrose phosphate synthase (SPS) gene (SPS3), one protein related to disease resistance gene (RGA3) and one immune protein gene (R1B-17). The activity assay of LAC, NCED, PAP and SPS revealed that the activities of these enzymes in the resistant population were significantly higher than those in the sensitive population at 0 h and after FE application at 12 h, 24 h and 72 h. Nevertheless, whether LAC, NCED, PAP and SPS genes were involved in herbicide metabolism needs to be further validated. Our results revealed that CYP, ABC transporter and LAC genes may participate in A. japonicus resistance. These genes identified in the present study provide new insights into the resistance mechanism of weeds in response to herbicide. Our study also implies the complexity of the NTSR mechanisms of weeds.

Drought stress-induced the formation of heteromorphic leaves of Populus euphratica Oliv: evidence from gene transcriptome.

Populus euphratica Oliv., a dominant species of arid desert community, grows heteromorphic leaves at different crown positions. Whether heteromorphic leaves are a strategy of plant adaptation to drought stress is rarely reported. This study sequenced the transcriptome of three typical heteromorphic leaves (lanceolate, ovate and broad-ovate leaves) of P. euphratica, and measured their drought stress. We wanted to reveal the molecular mechanisms underlying the formation of heteromorphic leaves. Drought stress was increased significantly from lanceolate to ovate to broad-ovate leaves. Gene ontology (GO) and KEGG enrichment analysis showed that the MADs-box gene regulated the expression of peroxidase (POD) in the phenylpropane biosynthetic pathway. The up-regulated expression of the chalcone synthase (CHS) gene in broad-ovate leaves significantly activated the flavonoid biosynthetic pathway. In the process of leaf shape change, the different expressions of homeodomain leucine zipper (HD-ZIP) among the three heteromorphic leaves had potential interactions on the AUX and ABA pathways. The expression of Sucrose phosphate synthase (SPS) and sucrose synthase (SUS) increased from lanceolate to broad-ovate leaves, resulting in a consistent change in starch and sucrose content. We concluded that these resistance-related pathways are expressed in parallel with leaf formation genes, thereby inducing the formation of heteromorphic leaves. Our work provided a new insights for desert plants to adapt to drought stress.

Beneficial effects of triadimefon in overcoming drought stress in soybean at fluorescence stage

Soybean (Glycine max [L.] Merr.) at fluorescence stage frequently experiences drought stress. Although triadimefon has been observed to improve drought tolerance of plants, reports on its role in drought resistance on leaf photosynthesis and assimilate transport are limited. This study examined the effects of triadimefon on leaf photosynthesis and assimilate transport at fluorescence stage of soybean experiencing drought stress. Results showed that triadimefon application relieved the inhibitory effects of drought stress on photosynthesis and increased RuBPCase activity. Drought increased soluble sugar contents, yet reduced starch content in the leaves by heightening the activities of sucrose phosphate synthase (SPS), fructose-1,6-bisphosphatase (FBP), invertase (INV), and amylolytic enzyme, impeding the translocation of carbon assimilates to roots and reducing plant biomass. Nevertheless, triadimefon elevated starch content and minimized sucrose degradation by augmenting sucrose synthase (SS) activity and restraining the activities of SPS, FBP, INV, and amylolytic enzyme compared with drought alone, regulating the carbohydrate balance of drought-stressed plants. Therefore, triadimefon application could reduce the photosynthesis inhibition and regulate the carbohydrate balance of drought-stressed soybean plants to lessen the impacts of drought on soybean biomass.

Sucrose metabolism analysis in a high sucrose sugarcane mutant clone at a mature stage in contrast to low sucrose parental clone through the transcriptomic approach

BackgroundThe significance of sugarcane as a major crop is due to the production of sucrose and a significant source of ethanol. Sucrose phosphate synthase (SPS), Sucrose synthase (SuSy), and cell wall invertase (CWIN) genes regulate sucrose metabolism and accumulation in high sucrose sugarcane; such genes are significant for manipulating sucrose content. The current study explored the genes associated with sucrose metabolism and accumulation in a high sucrose sugarcane mutant clone GXB9 compared to its low sucrose parental clone B9.ResultsA total of 100, 262 differentially expressed genes were obtained, and 69, 637 (69.46%) got annotation in public databases COG, GO, KEGG, KOG, Pfam, eggNOG, NR, and Swiss-Prot. The SPS5 gene was significantly up-regulated in the maturing internodes of GXB9 and downregulated in B9. The SuSy and CWIN genes were up-regulated in the immature internodes; however, no expression was found in the maturing internodes of GXB9. The genes involved in trehalose synthesis were downregulated in GXB9 while up-regulated in B9. The cellulose synthase (CeS) genes were significantly up-regulated in the immature internodes than in maturing internodes of GXB9.ConclusionsThe key finding of this research suggests that the SPS5 gene has a predominant role in enhancing the sucrose accumulation ability of GXB9. No expression of SuSy and CWIN genes in maturing internodes and downregulation of trehalose genes in GXB9 may also have contributed to the higher sucrose accumulation in the stalk of high sucrose mutant. The current finding is a source for sugarcane breeding, particularly improving sucrose content.Graphical

Genome-wide identification and function analysis of the sucrose phosphate synthase MdSPS gene family in apple

Sucrose phosphate synthase (SPS) is a rate-limiting enzyme that works in conjunction with sucrose-6-phosphate phosphatase (SPP) for sucrose synthesis, and it plays an essential role in energy provisioning during growth and development in plants as well as improving fruit quality. However, studies on the systematic analysis and evolutionary pattern of the SPS gene family in apple are still lacking. In the present study, a total of seven MdSPS and four MdSPP genes were identified from the Malus domestica genome GDDH13 v1.1. The gene structures and their promoter cis-elements, protein conserved motifs, subcellular localizations, physiological functions and biochemical properties were analyzed. A chromosomal location and gene-duplication analysis demonstrated that whole-genome duplication (WGD) and segmental duplication played vital roles in MdSPS gene family expansion. The Ka/Ks ratio of pairwise MdSPS genes indicated that the members of this family have undergone strong purifying selection during domestication. Furthermore, three SPS gene subfamilies were classified based on phylogenetic relationships, and old gene duplications and significantly divergent evolutionary rates were observed among the SPS gene subfamilies. In addition, a major gene related to sucrose accumulation (MdSPSA2.3) was identified according to the highly consistent trends in the changes of its expression in four apple varieties (‘Golden Delicious’, ‘Fuji’, ‘Qinguan’ and ‘Honeycrisp’) and the correlation between gene expression and soluble sugar content during fruit development. Furthermore, the virus-induced silencing of MdSPSA2.3 confirmed its function in sucrose accumulation in apple fruit. The present study lays a theoretical foundation for better clarifying the biological functions of the MdSPS genes during apple fruit development.

Irrigation regimes modulate non-structural carbohydrate remobilization and improve grain filling in rice (Oryza sativa L.) by regulating starch metabolism

Recently developed ‘super’ rice cultivars with greater yield potentials often suffer from the problem of poor grain filling, especially in inferior spikelets. Here, we studied the activities of enzymes related to starch metabolism in rice stems and grains, and the microstructures related to carbohydrate accumulation and transportation to investigate the effects of different water regimes on grain filling. Two ‘super’ rice cultivars were grown under two irrigation regimes of well-watered (WW) and alternate wetting and moderate soil drying (AWMD). Compared with the WW treatment, the activities of ADP glucose pyrophosphorylase (AGPase), starch synthase (StSase) and starch branching enzyme (SBE), and the accumulation of non-structural carbohydrates (NSCs) in the stems before heading were significantly improved, and more starch granules were stored in the stems in the AWMD treatment. After heading, the activities of α-amylase, β-amylase, sucrose phosphate synthase (SPS) and sucrose synthase in the synthetic direction (SSs) were increased in the stems to promote the remobilization of NSCs for grain filling under AWMD. During grain filling, the enzymatic activities of sucrose synthase in the cleavage direction (SSc), AGPase, StSase and SBE in the inferior spikelets were increased, which promoted grain filling, especially for the inferior spikelets under AWMD. However, there were no significant differences in vascular microstructures. The grain yield and grain weight could be improved by 13.1 and 7.5%, respectively, by optimizing of the irrigation regime. We concluded that the low activities of key enzymes in carbon metabolism is the key limitation for the poor grain filling, as opposed to the vascular microstructures, and AWMD can increase the amount of NSC accumulation in the stems before heading, improve the utilization rate of NSCs after heading, and increase the grain filling, especially in the inferior spikelets, by altering the activities of key enzymes in carbon metabolism.

Panicle removal delays plant senescence and enhances vegetative growth improving biomass production in switchgrass

Switchgrass (Panicum virgatum L.) shows great bioenergy potential and provides multiple ecological services. However, its severe seed shedding causes biomass waste and seed diffusion risk. Questions arise as to the production performance of switchgrass after panicle removal (PR), which remains unknown. We revealed switchgrass growth responses to PR and illustrated physiological reasons. Compared to the untreated switchgrass, PR significantly stimulated stem elongation (32.13%) and increased tiller number (39.70%), as well as aboveground biomass (24.69%). Importantly, PR significantly increased contents of nonstructural carbohydrates (NSCs) in the stem, which was directly beneficial to the ethanol conversion, and in the rhizome and root. The chlorophyll contents, net photosynthetic efficiency, and photochemical quantum efficiencies of flag leaf increased significantly. PR switchgrass allocated more assimilates into the stem, root, rhizome, and NSCs. Activities of phosphoenolpyruvate carboxylase, ribulose-1, 5-diphosphate carboxylase, sucrose phosphate synthase (SPS) in flag leaf and adenosine diphosphate glucose pyrophosphorylase (AGPase) and SPS in the stem and rhizome all increased significantly. In contrast, activities of the AGPase in flag leaf and sheath decreased significantly. Contents of zeatin nucleoside, gibberellins, and indoleacetic acid in flag leaf, stem, and rhizome all increased. Abscisic acid contents in flag leaf and stem decreased significantly while increased significantly in the rhizome. In conclusion, growth-promoting hormones delayed plant senescence, enhanced leaf photosynthesis, and enhanced vegetative growth through regulating assimilates-metabolism-related enzymes, which increased biomass accumulation in PR switchgrass. This work provided new insights for yield and digestibility improvement in switchgrass through field management practices, hormones regulation, or genetic modification strategies.

Foliar application of fish protein peptide improved the quality of deep-netted melon

To improve the fruit quality of deep-netted melon, fish protein peptide (FPP) with a total protein content greater than 90% at a concentration of 1 g·L−1 was sprayed on leaves after pollination, distilled water was sprayed on the control plants (CK). Field indices such as single melon fresh mass, commercial fruit rate, yield and fruit nutrient contents were evaluated. Soluble sugar, starch, organic acid and the activities of enzymes related to sugar metabolism in the inner, middle and outer layers of melon flesh were also determined. The results showed that the commercial fruit rate and yield per hectare increased by 8.96% and 5.98%, respectively. Nutrient contents increased, including the total amounts of 16 amino acids were 0.34 g/100 g higher than those of CK, and the mineral element contents increased by 15.79%, among which the contents of potassium, phosphorus, zinc, calcium, magnesium and molybdenum were significantly different from those of CK (p < 0.05). FPP treatment significantly increased the soluble sugar content in the outer layer of the mesocarp of deep-netted melon and the ascorbic acid contents in the inner and middle layers of the mesocarp of deep-netted melon. FPP increased sucrose accumulations in fruit by decreasing the activity of neutral invertase (NI), increasing the activity of sucrose phosphate synthase (SPS) and the synthesis direction of sucrose synthase (SS), and by increasing the glucose and fructose contents by enhancing the activity of acid invertase (AI). These findings suggest that exogenous FPP improves the commercial fruit rate, yield, and quality of deep-netted melon.