Neutral Invertase Activity Research Articles

Hydrogen sulfide alleviates pericarp browning in lichi fruit by modulating energy and sugar metabolisms.

Postharvest litchi is susceptible to browning that limits the development of litchi industry. Hydrogen sulfide (H2S) is an important bioactive molecule that can regulate many physiological processes. This study examined the effects of exogenous H2S on pericarp browning and related physiological mechanisms in postharvest litchi. The results exhibited that exogenous H2S treatment delayed the browning of litchi pericarp and reduced the damage to cell membrane integrity during storage. This treatment inhibited the energy losses of litchi fruit by increasing the activities of H+-ATPase, Ca2+- ATPase, cytochrome C oxidase (CCO) and succinate dehydrogenase (SDH) and regulating the expression of energy metabolism-related genes, including LcAtpB, LcSnRK2, LcAAC1, LcAOX1 and LcUCP1. In addition, H2S treatment increased the levels of fructose, glucose, sucrose, inositol, galactose and sorbose in litchi fruit, and promoted sucrose synthesis by regulating the activities of sucrose phosphate synthase (SPS), sucrose synthase (SS), acid invertase (AI) and neutral invertase (NI). Based on the current findings, we suggest that exogenous H2S enhances the energy supply and antioxidant activity of litchi by modulating energy and sugar metabolism, thereby inhibiting fruit browning and senescence. These results indicated that H2S treatment is an effective approach to maintaining the quality of litchi fruit and extending its shelf life.

Potassium indole-3-butyric acid affects rice's adaptability to salt stress by regulating carbon metabolism, transcription factor genes expression, and biosynthesis of secondary metabolites.

Soil salinity pollution is increasing worldwide, seriously affecting plant growth and crop production. Existing reports on how potassium indole-3-butyric acid (IBAK) regulates rice salt stress adaptation by affecting rice carbon metabolism, transcription factor (TF) genes expression, and biosynthesis of secondary metabolites still have limitations. In this study, an IBAK solution at 40 mg L-1 was sprayed on rice leaves at the seedling stage. The results showed that the IBAK application could promote shoot and root growth, decrease sucrose and fructose content, increase starch content, and enhance acid invertase (AI) and neutral invertase (NI) activity under salt stress, indicating altered carbon allocation. Furthermore, the expression of TF genes belonging to the ethylene responsive factor (ERF), WRKY, and basic helix-loop-helix (bHLH) families was influenced by IBAK. Many key genes (OsSSIIc, OsSHM1, and OsPPDKB) and metabolites (2-oxoglutaric acid, fumaric acid, and succinic acid) were upregulated in the carbon metabolism pathway. In addition, this study highlighted the role of IBAK in regulating the biosynthesis of secondary metabolites pathway, potentially contributing to rice stress adaptability. The results of this study can provide new sustainable development solutions for agricultural production.

The ameliorative effects of exogenous methyl jasmonate on grapevines under drought stress: Reactive oxygen species, carbon and nitrogen metabolism

Drought stress is recognized as one of the foremost abiotic stresses for worldwide agriculture. Methyl jasmonate (MeJA) is a vital phytohormone that is involved in plant growth, development, and stress adaptation. This study aimed to investigate the influence of exogenous MeJA on carbon and nitrogen metabolism in grapevine leaves under drought stress. Two-year-old grape cuttings (Vitis vinifera L.) were foliar sprayed with either 100 μM MeJA solution or distilled water and then exposed to drought stress. The results showed that exogenous MeJA increased the activities of superoxide dismutase (21 %) and catalase (16 %), resulting in decreased accumulation of reactive oxygen species. Drought stress critically disturbed the processes of photosynthesis, sucrose and starch metabolism, nitrogen assimilation, and amino acid metabolism. MeJA pretreatment improved the photosynthetic capacity and decreased the activities of sucrose synthase (31 %), acid invertase (15 %), and neutral invertase (27 %), thereby improving the accumulation of starch (10 %) and sucrose (90 %). In addition, MeJA pretreatment promoted nitrogen assimilation under drought stress. An increase in activities of nitrate reductase (60 %) and glutamine synthetase (13 %), and a decrease in NH4+ content was observed. Meanwhile, the MeJA application promoted the accumulation of proline and γ-aminobutyric acid, which contributed to the osmotic adjustment and ROS scavenging. In conclusion, exogenous MeJA could promote drought tolerance of grapevines by alleviating oxidative damage and regulating carbon and nitrogen metabolism.

Dark septate endophyte Anteaglonium sp. T010 promotes biomass accumulation in poplar by regulating sucrose metabolism and hormones.

Plant biomass is a highly promising renewable feedstock for the production of biofuels, chemicals and materials. Enhancing the content of plant biomass through endophyte symbiosis can effectively reduce economic and technological barriers in industrial production. In this study, we found that symbiosis with the dark septate endophyte (DSE) Anteaglonium sp. T010 significantly promoted the growth of poplar trees and increased plant biomass, including cellulose, lignin and starch. To further investigate whether plant biomass was related to sucrose metabolism, we analyzed the levels of relevant sugars and enzyme activities. During the symbiosis of Anteaglonium sp. T010, sucrose, fructose and glucose levels in the stem of poplar decreased, while the content of intermediates such as glucose-6-phosphate (G6P), fructose-6-phosphate (F6P) and UDP-glucose (UDPG), and the activity of enzymes related to sucrose metabolism, including sucrose synthase (SUSY), cell wall invertase (CWINV), fructokinase (FRK) and hexokinase, increased. In addition, the contents of glucose, fructose, starch, and their intermediates G6P, F6P and UDPG, as well as the enzyme activities of SUSY, CWINV, neutral invertase and FRK in roots were increased, which ultimately led to the increase of root biomass. Besides that, during the symbiotic process of Anteaglonium sp. T010, there were significant changes in the expression levels of root-related hormones, which may promote changes in sucrose metabolism and consequently increase the plant biomass. Therefore, this study suggested that DSE fungi can increase the plant biomass synthesis capacity by regulating the carbohydrate allocation and sink strength in poplar.

Storage Temperature Affects the Accumulation of Phenolics in Fresh-Cut Melon by Accelerating the Sucrose Decomposition

To accurately evaluate the role of storage temperature in improving the quality of fresh-cut fruits and vegetables, the effects of two storage temperatures (5 °C and 15 °C) on the phenylpropanoid pathway and sucrose metabolism in fresh-cut melon (cv. Yugu) cubes were determined. A higher temperature (15 °C) expedited sucrose decomposition in the melon cubes at the early stage of storage, resulting in higher levels of glucose and fructose. This effect was corroborated by increased activities of acid invertase (AI), neutral invertase (NI), and sucrose synthase cleavage (SS-c), along with higher expressions of CmAI1/2, CmNI1/2, and CmSS1/2 in the melon cubes at 15 °C. Additionally, the higher activity and gene expression of hexokinase in melon cubes at 15 °C led to an increase in the utilization rate of sugars toward downstream metabolic pathways. Moreover, the melon cube storage at 15 °C elevated the activities and gene expressions of phenylalanine ammonia lyase (PAL), cinnamic acid 4-hydroxylase (C4H), and 4-coumaric acid: CoA ligase (4CL), thereby increasing the synthesis of phenolics. Sucrose showed a significant negative correlation with PAL, C4H, and 4CL, as well as with CmPAL5/7 and CmC4H1/3. However, hexokinase displayed a significant positive correlation with PAL, C4H, and 4CL, as well as with CmPAL1, CmPAL3-9, CmC4Hs, and Cm4CLs. These findings demonstrate that a higher-temperature storage of melon cubes can accelerate the phenylpropanoid pathway and sucrose metabolism by regulating the activity and gene expression of related enzymes, thereby inducing phenolic accumulation. These results also indicate that lower-temperature storage is not conducive to the conversion of sugars into phenolics in fresh-cut melon. Therefore, the temperature can be appropriately and briefly raised in the production and preservation process of fresh-cut melon to obtain higher levels of phenolics.

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.

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

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.

Reactive oxygen species homeostasis and carbohydrate metabolism involved in wound healing of carrot induced by hot water treatment

Although the information on regulation of reactive oxygen species (ROS) homeostasis or carbohydrate metabolism has been published in other wounding-responsive horticultural crops, the involvement of that in carrot remains unknown, especially treatment with hot water. In this study, ROS and carbohydrate metabolism analysis during wound healing was performed to clarify the underlying mechanism for the wounded carrots subjected to hot water treatment. Results showed that 45 ℃ hot water promoted NADPH oxidase (NOX) and superoxide dismutase (SOD) activities in healing carrots, elevated O2·− and H2O2 contents. Also, hot water enhanced catalase (CAT) and peroxidase (POD) activities, the activities of AsA-GSH cycle-related as well as the ascorbic acid and glutathione levels. Additionally, hot water stimulated acid invertase (AI) and neutral invertase (NI) activities with a higher level of sucrose, fructose and glucose, triggered stronger activities of hexokinase (HK), phosphofruc tokinase (PFK), pyruvate kinase (PK) and glucose-6-phosphate dehydrogenase (G-6-PDH) in glycolytic and pentose phosphate pathway (PPP) during healing of carrots. Taken together, hot water can regulate ROS homeostasis and activate sucrose metabolism, glycolysis and PPP pathway to benefit carrot wound healing.

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.

L-Glutamate maintains the quality of apple fruit by mediating carotenoid, sorbitol and sucrose metabolisms.

l-Glutamate is involved in many important chemical reactions in horticultural products and improves postharvest disease resistance. Quality decline of apple fruit caused by senescence and fungus invasion often leads to tremendous losses during logistics. This study was performed to evaluate the variations of quality attributes, carotenoid, sorbitol and sucrose metabolisms in apples (cv. Qiujin) after l-glutamate dipping treatment. l-Glutamate immersion maintained high values of L*, a* and b*, flesh firmness, titratable acidity, as well as the total soluble solids, soluble sugar, reducing sugar and ascorbic acid contents in apples. l-Glutamate also decreased mass loss, respiratory rate and ethylene release, enhanced sucrose synthase-cleavage, acid invertase and neutral invertase activities, whereas reduced sorbitol dehydrogenase, sucrose phosphate synthase, sucrose synthase synthesis and sorbitol oxidase activities in apples. Moreover, l-glutamate inhibited lutein, β-carotene and lycopene accumulation, and down-regulated phytoene synthase, lycopene β-cyclase, ζ-carotene desaturase, phytoene desaturase, carotenoid isomerase, ζ-carotene isomerase and carotenoids cleavage dioxygenase gene expressions, but up-regulated 9-cis-epoxycarotenoid dioxygenase gene expression in apples. Postharvest l-glutamate dipping treatment can keep apple quality by modulating key enzyme activity and gene expression in sorbitol, sucrose and carotenoid metabolisms. © 2023 Society of Chemical Industry.

Cut-Wounding Promotes Phenolic Accumulation in Cucumis melo L. Fruit (cv. Yugu) by Regulating Sucrose Metabolism

The effect of cutting on the molecular changes underlying sucrose metabolism and the phenylpropanoid pathway in melon fruit (cv. Yugu) during storage at 15 °C was investigated. Furthermore, the key metabolites, enzymes, and genes involved in sucrose and phenylpropanoid metabolism were determined. Results showed that the cutting of melon increased the activities of acid invertase (AI), neutral invertase (NI), and sucrose synthase-cleavage (SS-c) and the expressions of CmAI1/2, CmNI1/2, and CmSS1, while sucrose synthase-synthesis (SS-s) and sucrose phosphate synthase (SPS) activities and the CmSS2/3 and CmSPS1/2/4 gene expressions were suppressed. These led to sucrose decomposition and fructose and glucose accumulation in fresh-cut melon at the early stage of storage. Moreover, cutting increased the activity and gene expression of hexokinase, which accelerated the transformation of hexose in fresh-cut melon. In addition, cutting enhanced the activities of phenylalanine ammonia lyase (PAL), cinnamate-4-hydroxylase (C4H), and 4-coumarate-CoA ligase (4CL) and up-regulated the expressions of CmPAL1-9, CmC4H1-4, and Cm4CL1/2/3, which activated phenylpropanoid metabolism and resulted in phenolic accumulation in fresh-cut melon. These findings demonstrate that cutting of melon can enhance sucrose metabolism and phenylpropanoid pathway by regulating the activities and gene expressions of related enzymes. Therefore, cut-wounding promoted the conversion of sugars to supply the necessary substrates for phenolic accumulation in fresh-cut melon.

Effects of Continuous Straw Returning on Soil Functional Microorganisms and Microbial Communities

This study examined the changes in soil enzymatic activity, microbial carbon source metabolic diversity, and straw decomposition rates in paddy fields treated with 1, 2, or 3years of straw returning (SR1-SR3). The soil's ability to decompose straw and cellulolytic bacteria increased with the number of treatment years (1: 31.9% vs. 2: 43.9% vs. 3: 51.9%, P < 0.05). The numbers of Azotobacter, Nitrobacteria, cellulolytic bacteria, and inorganic phosphate bacteria increased progressively with the numbers of straw returning years. Cellulolytic bacteria and inorganic phosphate bacteria were significantly positively correlated with the decomposition rate (r = 0.783 and r = 0.375, P < 0.05). Based on 16S sequencing results, straw returning improved the microbial diversity of paddy soils by increasing unclassified bacteria and keeping dominant soil microorganism populations unchanged. The relative importance of individual microbial taxa was compared using random forest models. Proteobacteria, ammoniating bacteria, and potassium dissolving bacteria contributed to peroxidase activity. The significant contributors to phosphate monoesterase were Acidobacteriota, Desulfobacterota, ammoniating bacteria, cellulolytic bacteria, and potassium-dissolving bacteria. Proteobacteria, ammoniating bacteria, cellulolytic bacteria, and potassium-dissolving bacteria contributed to urease activity. Desulfobacterota, ammoniating bacteria, cellulolytic bacteria, and potassium-dissolving bacteria contributed to the neutral invertase activity. In conclusion, soil microbial community structure and function were affected within 2years of straw returning, which was driven by the combined effects of soil organic carbon, available nitrogen, available potassium, and pH. With elapsing straw returning years, soil properties interacted with soil microbial communities, and a healthier soil micro-ecological environment would form.

Physiological and transcriptome analyses reveal that mid-fruit load improves the strength of source and sink in grapevine (Vitis Vinifera L.)

• In the present study, the assay for biochemical and molecular mechanism were used by 13 C labeling, full-length RNA-seq and gene transformation. • We make a conclusion that 50%FL significantly improved the source and sink strength. As a prime candidate gene, overexpression of VvPUP1 in grape cells improved its sugar accumulation. • These results demonstrates that the optimal fruit load was about 50%. Appropriately adjusting fruit loads (FL) can promote plant productivity in the field. In the present study, physiological, transcriptomic, and gene function assays were conducted by 13 C labeling, full-length RNA-seq, and gene transformation. A comparative analysis of three different FL treatments (25%FL, 50%FL, and 100% FL) was performed to identify the mechanism that response to different FL. The results showed that 50%FL significantly improved the source strength by enhancing photosynthesis. The sink strength of 50%FL also reached the maximum when considering soluble sugar, weight, 13 C allocation, sugar metabolism-related enzyme activity, and composition in berries, and yield. In addition, full-length transcriptome profiling exploited 1,098 differently expressed genes (DEGs) in 25%FL and 100%FL, and 1,479 DEGs in 50%FL and 100%FL, respectively. Thirty-four genes, including PUP1 and FBA1 , were identified in carbon transport and metabolism-related pathways. As a major candidate gene, VvPUP1 was found to enhance sugar accumulation when overexpressed in grape cells. The transgenic cells had high soluble sugar contents and sucrose synthase (SS), neutral invertase (NI), and sucrose phosphate synthase (SPS) activities. Overexpression of VvPUP1 in tomatoes increased fruit size and weight, soluble sugar concentration, and the expression levels of SlSUS1, SlSPS1 , and SlBGLU13 , suggesting that VvPUP1 can promote berry enlargement and sugar accumulation. These results provide novel insights into the response of grapevine to different FL, demonstrating the differences in the source (leaf) and sink (berry) strength among different FL grapes.

Exogenous Si Mitigates the Effects of Cinnamic-Acid-Induced Stress by Regulating Carbon Metabolism and Photosynthetic Pigments in Cucumber Seedlings

(1) Background: Cinnamic acid (CA) is a harmful substance secreted by the roots of continuous-cropping crops. (2) Methods: This study aimed to investigate how exogenous Si affects chlorophyll content and carbon metabolism in cucumber seedlings under CA-induced stress. (3) Results: The levels of chlorophyll a, chlorophyll b, chlorophyll a+b, and carotenoids were significantly reduced due to CA-induced stress. The addition of exogenous Si significantly alleviated this reduction. Under CA-induced stress, exogenous Si significantly increased the activities of ribulose-1,5-bisphosphate carboxylase, glyceraldehyde-3-phosphate dehydrogenase, fructose-1,6-bisphosphatase, fructose-1,6-bisphosphate aldolase, and transketolase. CA-induced stress significantly increased the fructose, glucose, and sucrose contents and reduced the starch content in the leaves and roots of seedlings. Similarly, the sucrose phosphate synthase, sucrose synthase, acid invertase, and neutral invertase activities were significantly reduced in plants under CA-induced stress. Overall, exogenous Si significantly reduced the soluble sugar content, increased the starch content, and promoted sucrose metabolism-related enzymatic activity in seedlings. (4) Conclusion: Exogenous Si can effectively increase the content of photosynthetic pigments in leaves of seedlings and maintain the balance of osmotic potential in the plant by reducing the accumulation of carbon assimilation products, which ultimately promotes tolerance to CA-induced autotoxicity stress.

Effects of foliar-spraying nitric oxide on the carbon metabolism enzymes activities and nutrients in leaves and roots of Reaumuria soongorica (pall.) maxim seedlings under NaCl stress

Salinity affects the growth of Reaumuria soongorica. Nitric oxide (NO) is a plant signaling molecule that can improve the stress resistance of R. soongorica. To date, studies on the salt tolerance of R. soongorica have mainly focused on its physiological and biochemical indexes. While the useful role of NO in plant response to salt stress and the molecular mechanisms of carbon metabolism in R. soongorica have scarcely been reported. Therefore, sodium nitroprusside (SNP) as NO donor (0, 0.01, 0.10, 0.25, 0.50, 1.0 mmol L−1) was used to determine the effects of NaCl stress on carbon metabolism and salt resistance in R. soongorica. Principal component and membership function analysis were used to select the best carbon metabolism indexes, optimal SNP concentration, and their ability to alleviate NaCl stress. The results showed that 300 mmol L−1 NaCl alone inhibited carbon metabolism and SNP promoted the adaptation of R. soongorica to NaCl stress. The accumulation of total soluble sugar, sucrose, starch, and the activities of sucrose phosphate synthase (SPS) and sucrose synthase (SS) in leaves and roots decreased significantly. The SNP foliar spray significantly increased the content of total soluble sugar and sucrose in roots and leaves and the activities of SS, SPS, acid invertase (AI) and neutral invertase (NI) in leaves but decreased the activities of SS, AI and NI in roots. These results suggested that the best treatment for alleviating NaCl stress was 0.10 mmol L−1 SNP and that the ability to alleviate NaCl stress in R. soongorica could be evaluated based on the activities of soluble sugar, sucrose, NI, and total invertase (TI). This study provides a theoretical basis for the protection and utilization of R. soongorica under saline conditions and also provides a foundation for further research.

Effects of postharvest treatment with pullulan, calcium chloride, and chitosan on quality and sugar metabolism of Annona squamosa during storage

In this study, the effects of postharvest treatment with 1% pullulan, 2% calcium chloride, and 1% chitosan on the physiological and biochemical properties, enzymatic activities and the differentially expressed genes (DEGs) with sucrose metabolism of Annona squamosa L. fruits stored at 15 ± 1°C for 12 days were investigated. Exogenous substances treatment retained a higher level of firmness, surface color, total soluble solids, organic acids, and tvolatile flavor substances compared to the control fruit. Exogenous substances treatments, particularly calcium chloride, enhanced sucrose phosphate synthase activity, whereas it inhibited acid invertase (AI) and neutral invertase (NI) activities. These changes in enzyme activities together resulted in a significantly higher sucrose content and lower glucose and fructose contents. The number (1550 genes), proportion (6.46%), and expression levels of DEGs in the calcium chloride-treated fruit, which was enriched in the starch and sucrose metabolism pathways, were all significantly higher than in chitosan treatment. The findings indicated that exogenous calcium chloride might alter sucrose metabolism during fruit ripening by regulating the enzymatic activities and metabolism pathway. This will provide a theoretical basis for further research on the regulation of sugar metabolism by exogenous substances treatment to solve the problem of quality degradation in the storage of A. squamosa. Novelty impact statement This study indicated that the application of chitosan, pullulan, or calcium chloride, especially calcium chloride treatment, can effectively maintain the quality of Annona squamosa fruit during storage. It was found that exogenous calcium chloride might alter sucrose metabolism during fruit ripening by regulating the enzymatic activities and metabolism pathway. The results provided a theoretical basis for exploring the mechanism of exogenous substances for maintaining the postharvest quality and enhancing the shelf life of A. squamosa fruit in further research.

Abnormal behavior of chilling injury in postharvest papaya fruit is associated with sugar metabolism.

In the most chilling-sensitive fruits and vegetables, usually, the lower the storage temperature, the more serious the symptoms of chilling injury (CI). As one of the special cases, papaya fruits at 1℃ show slighter CI symptoms than those at higher storage temperature. Such abnormal CI phenomenon has not received enough attention and its mechanism is not clear. The present study investigated the difference of CI severity and sugar metabolism in papaya fruits when stored between 1℃ and 6℃. The results showed that CI index in papaya fruits preserved at 1°C was markedly lower than that in fruit at 6°C, which was accompanied by higher content of glucose, fructose, and sucrose. In addition, compared to 6°C, 1°C promoted higher activities of sucrose synthase, sucrose-phosphate synthase, and neutral invertase, but lowered acid invertase activity. RT-qPCR analysis showed that 1°C upregulated the CpSPS expression and downregulated the CpAI expression when compared to 6°C. The present results indicate that higher chilling tolerance in papaya fruit at 1°C could be attributed to more accumulation of sucrose and reducing sugars in relation to more advantageous sugar metabolism. These results provided a basis for explaining the abnormal behavior of papaya fruits in response to varying low temperatures. PRACTICAL APPLICATION: For most chilling-sensitive fruits and vegetables, in the range of temperatures that induce chilling injury (CI), the lower storage temperature may lead to more severe CI. However, as one of the special cases, papaya fruits at 1℃ show slighter CI symptoms than those at higher storage temperature. The reason for this abnormal CI symptom in papaya fruits is that 1°C storage can regulated enzyme activities and changes in gene expression related to sugar metabolism, which could result in more accumulation of sucrose and slower degradation of hexose and contribute to alleviation of CI. Our results provided a basis for explaining the abnormal behavior of papaya fruit in response to varying low temperatures.

Postharvest melatonin dipping maintains quality of apples by mediating sucrose metabolism

Senescence is a pivotal factor that causes quality breakdown and economic loss of fruit after harvest. In this study, ‘Golden Delicious’ apples were used as the materials to investigate the effect of melatonin dipping on quality parameters and sucrose metabolism during room temperature storage. Postharvest melatonin treatment inhibited respiratory intensity and ethylene release, increased flesh firmness, soluble sugar, ascorbic acid, and soluble solid contents, and titratable acid in apples. Furthermore, melatonin treatment inhibited acid invertase and neutral invertase activities, increased sucrose synthase and sucrose phosphate synthase activities, and repressed the activities of sorbitol dehydrogenase, sorbitol oxidase and sucrose synthase cleavage in apple fruit. All these findings suggest that exogenous application of melatonin could maintain quality of ‘Golden Delicious’ apples by mediating the enzyme activity in sucrose metabolism.

Effects of Salt-Alkaline Stress on Carbohydrate Metabolism in Rice Seedlings

The aim of this study was to investigate carbohydrate metabolism in rice seedlings subjected to salt-alkaline stress. Two relatively salt-alkaline tolerant (Changbai 9) and sensitive (Jinongda 138) rice cultivars, grown hydroponically, were subjected to salt-alkaline stress via 50 mM of salt-alkaline solution. The carbohydrate content and the activities of metabolism-related enzymes in the leaves and roots were investigated. The results showed that the contents of sucrose, fructose, and glucose in the leaves and roots increased under salt-alkaline stress. Starch content increased in the leaves but decreased in the roots under salt-alkaline stress. The activities of sucrose-phosphate synthase, sucrose synthase, amylase, and ADP-glucose pyrophosphorylase increased whereas the activities of neutral invertase and acid invertase decreased in the leaves under salt-alkaline stress. The activities of sucrose-phosphate synthase, sucrose synthase, amylase, neutral invertase, and acid invertase increased in the roots under salt-alkaline stress. In conclusion, salt-alkaline stress caused the accumulation of photosynthetic assimilates in the leaves and decreased assimilation export to the roots.