Pyruvate Decarboxylase Activity Research Articles

Effect of Hypoxic Stress and Levels of Mn on the Physiology and Biochemistry of Phyllostachys praecox.

Hypoxic environments have an adverse effect on the growth and development of P. praecox, and this is accompanied by the production of reducing substances such as Fe and Mn. In this study, the effect of hypoxic stress and Mn concentrations on leaf chlorophyll contents, root morphology, root activity, element absorption, antioxidant enzymes, and respiratory enzyme system of P. praecox were evaluated in a hydroponics environment. The results revealed that application of Mn2+ during hypoxic stress enhanced leaf chlorophyll contents and boosted up the indexes of the root system. The root activity of P. praecox was reduced with stresses of hypoxia. The treatment of Mn2+ initially improved and then decreased the root activity of P. praecox, and attained its maximum with application of 300 μmol/L Mn2+ compared with control. The indexes of antioxidant enzymes of P. praecox were higher than that of 8 mg/L oxygen concentrations except for variable superoxide dismutase (SOD) in the treatment of 300 μmol/L Mn2+ with hypoxia stress. The application of Mn had inhibited the absorption of mineral elements in P. praecox. The activities of pyruvate decarboxylase (PDC), alcohol dehydrogenase (ADH), and lactic dehydrogenase (LDH) were initially improved and then diminished with hypoxia stress. It is concluded that hypoxia is a key factor affecting the growth and degradation of P. praecox, while combining it with the increase of Mn concentration enhances the damage to Phyllostachys pubescens. Our research is helpful for the sustainable management and scientific fertilization management of Phyllostachys praecox.

The pyruvate decarboxylase activity of IpdC is a limitation for isobutanol production by Klebsiella pneumoniae

BackgroundKlebsiella pneumoniae contains an endogenous isobutanol synthesis pathway. The ipdC gene annotated as an indole-3-pyruvate decarboxylase (Kp-IpdC), was identified to catalyze the formation of isobutyraldehyde from 2-ketoisovalerate.ResultsCompared with 2-ketoisovalerate decarboxylase from Lactococcus lactis (KivD), a decarboxylase commonly used in artificial isobutanol synthesis pathways, Kp-IpdC has an 2.8-fold lower Km for 2-ketoisovalerate, leading to higher isobutanol production without induction. However, expression of ipdC by IPTG induction resulted in a low isobutanol titer. In vitro enzymatic reactions showed that Kp-IpdC exhibits promiscuous pyruvate decarboxylase activity, which adversely consume the available pyruvate precursor for isobutanol synthesis. To address this, we have engineered Kp-IpdC to reduce pyruvate decarboxylase activity. From computational modeling, we identified 10 amino acid residues surrounding the active site for mutagenesis. Ten designs consisting of eight single-point mutants and two double-point mutants were selected for exploration. Mutants L546W and T290L that showed only 5.1% and 22.1% of catalytic efficiency on pyruvate compared to Kp-IpdC, were then expressed in K. pneumoniae for in vivo testing. Isobutanol production by K. pneumoniae T290L was 25% higher than that of the control strain, and a final titer of 5.5 g/L isobutanol was obtained with a substrate conversion ratio of 0.16 mol/mol glucose.ConclusionsThis research provides a new way to improve the efficiency of the biological route of isobutanol production.

High relative humidity enhances chilling tolerance of zucchini fruit by regulating sugar and ethanol metabolisms during cold storage

High relative humidity (RH) cold room (RH: 98 ± 2%) controlled by a ‘dry fog’ system and normal cold room (RH: 74 ± 2%) were used to store zucchini fruit to investigate the regulation of high RH on chilling tolerance and sugar and ethanol metabolisms under cold stress. High RH storage inhibited chilling injury (CI) and maintained higher activities of sucrose synthase-synthesis and sucrose phosphate synthase and contents of glucose, fructose and sucrose in zucchini fruit. Meanwhile, high RH-stored fruit exhibited lower activities of hexokinase, phosphofructokinase, and pyruvate kinase as compared with the control. Besides, the accumulation of acetaldehyde and ethanol under cold stress was decreased by high RH storage together with the inhibition of the increase in activities of alcohol dehydrogenase, pyruvate decarboxylase and expressions of related genes. Taken together, high RH storage enhanced chilling tolerance in zucchini fruit by maintaining high levels of soluble sugars and inhibiting ethanol production.

Molecular mechanism of ethanol fermentation inhibition via protein tyrosine nitration of pyruvate decarboxylase by reactive nitrogen species in yeast

Protein tyrosine nitration (PTN), in which tyrosine (Tyr) residues on proteins are converted into 3-nitrotyrosine (NT), is one of the post-translational modifications mediated by reactive nitrogen species (RNS). Many recent studies have reported that PTN contributed to signaling systems by altering the structures and/or functions of proteins. This study aimed to investigate connections between PTN and the inhibitory effect of nitrite-derived RNS on fermentation ability using the yeast Saccharomyces cerevisiae. The results indicated that RNS inhibited the ethanol production of yeast cells with increased intracellular pyruvate content. We also found that RNS decreased the activities of pyruvate decarboxylase (PDC) as a critical enzyme involved in ethanol production. Our proteomic analysis revealed that the main PDC isozyme Pdc1 underwent the PTN modification at Tyr38, Tyr157, and Tyr344. The biochemical analysis using the recombinant purified Pdc1 enzyme indicated that PTN at Tyr157 or Tyr344 significantly reduced the Pdc1 activity. Interestingly, the substitution of Tyr157 or Tyr344 to phenylalanine, which is no longer converted into NT, recovered the ethanol production under the RNS treatment conditions. These findings suggest that nitrite impairs the fermentation ability of yeast by inhibiting the Pdc1 activity via its PTN modification at Tyr157 and Tyr344 of Pdc1.

Exogenous ABA promotes aroma biosynthesis of postharvest kiwifruit after low-temperature storage.

Exogenous ABA played a positive role in the accumulation and biosynthesis of aroma components of postharvest kiwifruit after low-temperature storage, especially the esters production during ripening. Low-temperature storage (LTS) generally affects the aroma formation associated with the decrease in aroma quality in kiwifruit. In this work, abscisic acid (ABA) treatment after LTS increased the production of aroma components in postharvest kiwifruit and enhanced the related enzyme activity, especially alcohol acyltransferase (AAT), branched amino acid transaminase (BCAT) and hydroperoxide lyase (HPL). Corresponding to the enzyme activity, the gene expression of AchnAAT, AchnADH, AchnBCAT and AchnHPL was significantly up-regulated by ABA. The principal component analysis further illustrated the differences in aroma components between ABA and the control. The positive correlation of aroma accumulation with the expression levels of AchnPDC and AchnLOX and the enzyme activities of BCAT and pyruvate decarboxylase (PDC) was also revealed by correlation analysis. In addition, the promoter sequences of the key genes involved in aroma biosynthesis contained multiple cis-elements (ABRE and G-box) of ABA-responsive proteins. Combining the transcriptome sequencing data, the promoting role of ABA signaling in the regulation of aroma biosynthesis of postharvest kiwifruit after LTS was discussed. This study would provide a reference for improving aroma quality of postharvest kiwifruit after LTS, as well the molecular mechanism of kiwifruit aroma fading after LTS.

Residue Analysis and the Effect of Preharvest Forchlorfenuron (CPPU) Application on On-Tree Quality Maintenance of Ripe Fruit in "Feizixiao" Litchi (Litchi chinensis Sonn.).

Litchi is a highly perishable fruit. Ripe litchi fruit loses quality quickly as they hang on tree, giving a very short hanging life and thus harvest period. This study attempted to explore the roles of cytokinin in regulating fruit ripening and senescence of litchi and examine the possibility of applying cytokinin in “on-tree storage” of the fruit. Exogenous cytokinin, forchlorfenuron (CPPU), was applied at 20 mg L−1 7 weeks after full bloom on litchi (Litchi chinensis cv. Feizixiao) fruit clusters. Color parameters, chlorophylls, anthocyanins, fruit and fruit part weights, total soluble solutes (TSSs), soluble sugars, organic acids, non-anthocyanin flavonoids, ethanol, and also CPPU residue in fruit were traced. CPPU residue was higher but decreased faster in the pericarp than in the aril, where it maintained < 10 μg kg−1. CPPU had no significant effect on fruit weight but tended to increase pericarp weight. The treatment suppressed chlorophyll loss and anthocyanin accumulation in the pericarp, increased non-anthocyanin flavonoids in the aril, but had no significant effects on non-anthocyanin flavonoids in the pericarp and total sugar and organic acids in the aril. As the commercially ripe fruit hanged on tree, TSSs, total sugar, and sucrose decreased with ethanol and acetic acid accumulation in the aril. CPPU significantly suppressed the loss of sucrose and total sugar and the accumulation of ethanol and acetic acid in the aril and inhibited malondialdehyde accumulation in the pericarp of the overripe fruit. Soluble invertase, alcohol dehydrogenase, and pyruvate decarboxylase (PDC) activity and gene expression in the aril were downregulated by CPPU. The results suggest that cytokinin partially suppresses the ripening process in litchi and is effective to slow quality loss in the overripe fruit on tree.

Effects of 1-methylcyclopropene (1-MCP) treatment on ethanol fermentation of Nanguo pear fruit during ripening.

The aim of this study was to analyze the effects of 1-methylcyclopropene (1-MCP) on ethanol fermentation of Nanguo pears during ripening. Pears were exposed to 1µl/L 1-MCP and stored at 20±2°C. Our data indicated that postharvest application of 1-MCP maintained flesh firmness and reduced ethylene production and respiration rate during storage compared with untreated fruits. 1-MCP treatment delayed the second glucose peak during fruit ripening. The contents of pyruvate and acetyl-CoA were generally reduced by 1-MCP treatment, and at the same time, their peaks were delayed by it during storage compared with controls. The contents of citric acid (CA) and oxaloacetate (OA) were increased by 1-MCP, whereas the contents of acetaldehyde and ethanol were reduced during the whole storage period compared with controls. Activities of alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDC) were reduced by application of 1-MCP during the early stage of storage, and the appearance of their peak activities was also delayed after treatment with 1-MCP. These data showed that postharvest application of 1-MCP could effectively delay the production of the "alcohol taste" of Nanguo pears during ripening. PRACTICAL APPLICATIONS: Nanguo pear is one of the most common cultivars that widely grow in northeast China. It is preferred by many consumers for its unique "alcohol taste", which is mainly produced through ethanol fermentation during ripening. Until now, the mechanisms for regulating ethanol fermentation in ripening Nanguo pears are still unclear. Our data indicated that postharvest application of the ethylene action inhibitor 1-MCP could effectively delay the production of the "alcohol taste" of Nanguo pears during ripening. The data from this study can provide reference data for maintaining the quality of postharvest Nanguo pears.

Assimilatory deficit and energy regulation in young Handroanthus chrysotrichus plants under flooding stress.

Flooding negatively influences the growth and development of several plant species. Here, we show that the flood tolerance of young Handroanthus chrysotrichus plants involves growth deficit, carbon assimilation reductions, starch remobilization, and energy regulation. The effect of hypoxia was evaluated in a controlled experiment consisting of plants subjected to normoxia and water-logging, with later recovery. We measured morphological changes, gas exchange, photosynthetic pigments, soluble carbohydrates and starch contents, the activity of the enzymes alcohol dehydrogenase (ADH), and pyruvate decarboxylase (PDC), and ATP and ADP levels. While control plants showed normal appearance and growth, flooded plants exhibited a drastic decrease in growth, necrosis of some root tips, hypertrophic lenticels on the stems, and foliar chlorosis. Oxygen deprivation in root cells led to a significant decrease in stomatal conductance. The low Amax rates caused a decline in foliar soluble sugar content at 20days and a subsequent increase in the leaves and roots, coinciding with starch degradation at 40days. We also observed increases of 220.5% in ADH and 292% in PDC activities in the roots at 20 and 40days of flooding. The activation of anaerobic metabolism in stressed plants was an essential mechanism for ATP regulation in both tissues used to maintain a minimal metabolism to cope with hypoxia to the detriment of growth. The post-stress recovery process in H. chrysotrichus occurred slowly, with gas exchange gradually resumed and anaerobic metabolism and sugar content maintained to improve energy regulation.

Melatonin and KNO3 Application Improves Growth, Physiological and Biochemical Characteristics of Maize Seedlings under Waterlogging Stress Conditions.

Simple SummaryWaterlogging is one of the serious abiotic stresses that retards plant growth and reduces crop productivity. Therefore, exploring effective ways for alleviating the impacts of waterlogging stress has important theoretical and practical applications. Melatonin is a pleiotropic molecule that influences many diverse actions to enhance plant growth. Therefore, investigating efficient waterlogging mitigation measures has both theoretical and practical significance. The objectives of the present research were to examine the efficiency of melatonin and KNO3 seed soaking and foliar application on alleviating the waterlogging inhibited growth performance of maize seedlings. The results showed that melatonin and KNO3 significantly improved the plant growth and biochemical parameters of maize seedlings under waterlogging stress conditions. Overall, the application of 100 µM melatonin with 0.50 g KNO3 via seed soaking and foliar spray can be used as a potential mitigating strategy for improving the growth of maize seedlings and alleviating the ill effects of waterlogging stress.Waterlogging is one of the serious abiotic stresses that inhibits crop growth and reduces productivity. Therefore, investigating efficient waterlogging mitigation measures has both theoretical and practical significance. The objectives of the present research were to examine the efficiency of melatonin and KNO3 seed soaking and foliar application on alleviating the waterlogging inhibited growth performance of maize seedlings. In this study, 100 µM melatonin and different levels (0.25, 0.50 and 0.75 g) of potassium nitrate (KNO3) were used in seed soaking and foliar applications. For foliar application, treatments were applied at the 7th leaf stage one week after the imposition of waterlogging stress. The results showed that melatonin with KNO3 significantly improved the plant growth and biochemical parameters of maize seedlings under waterlogging stress conditions. However, the application of melatonin with KNO3 treatments increased plant growth characteristics, chlorophyll content, and the net photosynthetic rate at a variable rate under waterlogging stress. Furthermore, melatonin with KNO3 treatments significantly reduced the accumulation of hydrogen peroxide (H2O2) and malondialdehyde (MDA), and it decreased the activity of pyruvate decarboxylase and alcohol dehydrogenase, while increasing enzymatic activities and soluble protein content of maize seedlings under waterlogging stress conditions. Overall, our results indicated that seed soaking with 100 µM melatonin and 0.50 g KNO3 was the most effective treatment that significantly improved the plant growth characteristics, chlorophyll content, photosynthetic rate, and enzymatic activity of maize seedling under waterlogging conditions.

Effects of abscisic acid (ABA) on ethanol fermentation during postharvest ripening of Nanguo pear fruit (Pyrus ussuriensis Maxim.)

The aim of this study was to explore the role of abscisic acid (ABA) in ethanol fermentation during postharvest ripening of Nanguo pear fruit (Pyrus ussuriensis Maxim.). Pears harvest at commercial maturity were treated with 100 μmol L−1 ABA or its biosynthesis inhibitor nordihydroguaiaretic acid (NDGA). Our data indicated that ABA treatment promoted respiration rate and ethylene production during ripening compared with controls, while NDGA treatment had the opposite effects. During the early ripening stage, flesh firmness in ABA treatment group was lower than in controls; while in NDGA treatment group, it was higher than in controls. The contents of glucose, ethanol and acetaldehyde were increased by ABA treatment while reduced by NDGA treatment during ripening compared with the controls. ABA treatment promoted pyruvate and acetyl-CoA contents, whereas application of NDGA reduced pyruvate content and delayed the peak of acetyl-CoA content compared with the controls. The oxaloacetic acid (OA) and citric acid (CA) contents were reduced by ABA treatment while increased by NDGA treatment during ripening. ABA treatment promoted pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) activities, whereas NDGA treatment reduced their activities mainly at the early ripening stage. Quantitative real-time polymerase chain reaction (qPCR) showed that expression of PDC1, ADH1 and ADH2 was differentially up-regulated by ABA treatment during ripening while down-regulated by NDGA treatment compared with the controls. PDC2 expression was enhanced after application of NDGA during ripening while reduced by ABA treatment at the early ripening stage. Our data indicated that ABA had a promoting effect on ethanol fermentation during ripening of Nanguo pear fruit.

Validation of mathematical model with phosphate activation effect by batch (R)-phenylacetylcarbinol biotransformation process utilizing Candida tropicalis pyruvate decarboxylase in phosphate buffer

The (R)-phenylacetylcarbinol (PAC) batch biotransformation kinetics for partially purified Candida tropicalis TISTR 5350 pyruvate decarboxylase (PDC) were determined to validate a comprehensive mathematical model in 250 mL scale with 250 mM phosphate buffer/pH 7.0. PDC could convert initial 100/120 mM benzaldehyde/pyruvate substrates to the statistical significantly highest (p ≤ 0.05) maximum PAC concentration (95.8 ± 0.1 mM) and production rate (0.639 ± 0.001 mM min−1). A parameter search strategy aimed at minimizing overall residual sum of square (RSST) based on a system of six ordinary differential equations was applied to PAC biotransformation profiles with initial benzaldehyde/pyruvate concentration of 100/120 and 30/36 mM. Ten important biotransformation kinetic parameters were then elucidated including the zeroth order activation rate constant due to phosphate buffer species (ka) of (9.38 ± < 0.01) × 10–6% relative PDC activity min−1 mM−1. The validation of this model to independent biotransformation kinetics with initial benzaldehyde/pyruvate concentration of 50/60 mM resulted in relatively good fitting with RSST, mean sum of square error (MSE), and coefficient of determination (R2) values of 662, 17.4, and 0.9863, respectively.

Effects of pyruvate decarboxylase (pdc1, pdc5) gene knockout on the production of metabolites in two haploid Saccharomyces cerevisiae strains

Saccharomyces cerevisiae has good reproductive ability in both haploid and diploid forms, a pyruvate decarboxylase plays an important role in S. cerevisiae cell metabolism. In this study, pdc1 and pdc5 double knockout strains of S. cerevisiae H14-02 (MATa type) and S. cerevisiae H5-02 (MATα type) were obtained by the Cre/loxP technique. The effects of the deletion of pdc1 and pdc5 on the metabolites of the two haploid S. cerevisiae strains were consistent. In S. cerevisiae H14-02, the ethanol conversion decreased by 30.19%, the conversion of glycerol increased by 40.005%, the concentration of acetic acid decreased by 43.54%, the concentration of acetoin increased by 12.79 times, and the activity of pyruvate decarboxylase decreased by 40.91% compared to those in the original H14 strain. The original S. cerevisiae haploid strain H14 produced a small amount of acetoin but produced very little 2,3-butanediol. However, S. cerevisiae H14-02 produced 1.420 ± 0.063 g/L 2,3-BD. This study not only provides strain selection for obtaining haploid strains with a high yield of 2,3-BD but also lays a foundation for haploid S. cerevisiae to be used as a new tool for genetic research and breeding programs.

Kinetics of Whole Cells and Ethanol Production from Candida tropicalis TISTR 5306 Cultivation in Batch and Fed-batch Modes Using Assorted Grade Fresh Longan Juice.

The kinetic profiles of Candida tropicalis TISTR 5306 cultivation based on modified yeast-malt (MYM), assorted grade fresh longan juice (AsgLG) and longan solid waste extract (LSWE) medium were evaluated in 1 l batch mode. The highest ethanol concentration level (25.5 ± 0.8 g/l) and ethanol yield - Yp/s of 0.491 ± 0.017 g ethanol/g consumed substrate, dried biomass concentration level (9.44 ± 0.05 g/l) and dried biomass yield - Yp/s of 0.533 ± 0.170 g dried biomass/g consumed substrate, specific pyruvate decarboxylase (PDC) activity (0.037 ± 0.003 U/mg protein) were achieved (p ≤ 0.05) in AsgLG medium. Scores ranking strategy were employed and AsgLG medium was subsequently selected with in the highest total score (p ≤ 0.05) of 698 ± 7 at 48 h. The cultivation in fed-batch mode with three rounds of pulse feeding (PF) in 1 l AsgLG medium was carried out. The apparent highest ethanol and dried biomass concentration levels with corresponding yields relative to time zero were (28.3 ± 0.5 g/l, 0.482 ± 0.012 g/g) at 120 h of PF2 and (9.39 ± 0.04 g/l, 0.110 ± 0.001 g/g) at 192 h of PF3. The maximum specific PDC activity was 0.057 ± 0.006 U/mg protein during PF1 feeding.

Nitric oxide increases the biomass and lint yield of field-grown cotton under temporary waterlogging through physiological and molecular regulation

• Foliar spray of exogenous nitric oxide increased its concentration in waterlogged cotton. • Increased nitric oxide concentration triggered a series of physiological and molecular events. • Foliar spray of nitric oxide ultimately reduced yield loss under waterlogging. Waterlogging is a major abiotic stress that reduces crop growth and productivity. Nitric oxide (NO) is an essential signaling molecule involved in abiotic stress responses in many plant species. However, it is unclear if and how NO mitigates waterlogging stress in field-grown cotton. In this study, the NO donor sodium nitroprusside (SNP) or its scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl -imidazoline-1-1-oxyl-3-oxide (cPTIO) was foliar-applied to waterlogged and non-waterlogged cotton plants. The NO concentrations in different plant parts, plant growth, yield and yield components, as well as related physiological and molecular events, were examined over three consecutive years under field conditions. Foliar application of SNP increased NO concentration in leaves by 83.6 and roots by 80.2 % under waterlogging, while cPTIO decreased the NO concentration by 18.9 and 5.3 %, respectively. Biomass and lint yield were reduced by 17.2 and 36.0 % under waterlogging without the application of SNP or cPTIO, but the reductions were 8.8 and 28.4 % following SNP application and 29.5 and 43.4 % respectively, following cPTIO application. Foliar applied SNP increased biomass by 10.2 % and lint yield by 12.0 % under waterlogging, whereas cPTIO caused 5.0 and 11.5 % reductions in biomass and lint yield. Quantitative real-time PCR analysis showed that the SNP up-regulated the NO synthesis gene (Gh NIR ), but down-regulated the genes involved in glycolysis and fermentation (Gh ADH 2 and Gh PDC ), ethylene production (Gh ACO and Gh ACS 8), and abscisic acid (ABA) synthesis (Gh NCED 2). It also reduced hydrogen peroxide (H 2 O 2 ) production and malonaldehyde (MDA) content in the leaves, but increased the leaf chlorophyll content and photosynthetic rate. The levels of auxin (IAA) and gibberellic acid (GA) were increased by SNP but those of ABA and ethylene contents as well as the activities of alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDC) in leaves were decreased. The cPTIO showed an opposite effect to SNP in almost all physiological and molecular responses to waterlogging. The overall results indicated that increasing the concentrations of NO in plant tissues via the foliar application of SNP mitigates waterlogging stress through a series of physiological and molecular events, ultimately reducing biological and lint yield loss under waterlogging. Therefore, increasing the concentration of NO in plant tissues by genetic breeding or agronomic measures might be a potential strategy for improving waterlogging tolerance and reducing yield loss in cotton.

Ethanol vapor treatment inhibits apple ripening at room temperature even with the presence of ethylene

Abstract The present study aimed to evaluate the effect of two ethanol vapor doses (250 and 500 ppm), 1-methylcyclopropene (1-MCP) (0.650 ppm) with or without ethylene application (150 ppm) on the aerobic and anaerobic metabolism and quality of ‘Elstar’, a fast ripening apple cultivar, and ‘Nicoter’, a slowly ripening apple cultivar, over 14 d of holding at room temperature (20 ± 2 °C). Fruit were subjected to treatments for 24 h and analyses performed after 0, 7 and 14 d holding at room temperature (20 ± 2 °C). For both cultivars studied, ethanol vapor treatments, especially 500 ppm, inhibited the ripening of apples even when combined with 150 ppm of ethylene, but not as much as 1-MCP treatment in ‘Nicoter’ apples. Fruit treated with ethanol vapor maintained lower electrolyte leakage, higher flesh firmness, greener color and had more healthy fruit. However, its application increased the pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) activity, acetaldehyde and ethyl acetate accumulation, but in concentrations below the odor threshold reported in the literature. The 1-MCP treatment increased decay incidence, reducing the healthy fruit amount in ‘Nicoter’ apples after 14 d, but maintained a very low ethylene production and respiration rate, which allowed higher acidity maintenance after 14 d holding at room temperature. There was no incidence of external and internal physiological disorders in both cultivars.

Mechanism of anoxic tolerance in backcross lines developed through Jyothi x Swarna-Sub 1 under submergence stress.

Rice varieties adapted to flash flood exhibit submergence tolerance by maintaining reduced shoot elongation under submerged conditions. This study focuses on the two main physiological traits leading to flash flood tolerance- high survival percentage with reduced shoot elongation under submergence and increased rate of alcoholic fermentation. Sub1introgressed BC3F2 lines exhibited higher survival percentage with moderate shoot elongation under submergence stress for fourteen days similar to the donor parent Swarna- Sub1. Enzymatic activities of alcohol dehydrogenase and pyruvate decarboxylase were monitored for fourteen days under submergence stress. The developed Sub1 introgressed lines and the donor parent Swarna-Sub1 showed higher rates of alcohol dehydrogenase and pyruvate decarboxylase activities under submergence stress thereby maintaining optimum rates of alcoholic fermentation. The findings of this study confirmed the expression of tolerance mechanism in the Sub1introgressedJyothi Backcross Inbred lines under submergence stress.

Growth and respiratory metabolic adaptation strategies of riparian plant Distylium chinense to submergence by the field study and controlled experiments

Submergence tolerance is crucial when thinking in promising species for restoration of ecosystems prone to suffer extreme flooding events. In this study, two-year-old seedlings of Distylium chinense were subjected to one field study and five controlled experiments: unsubmerged and watered daily as controls (CK) and completely submerged for 30, 60, 90 and 120 days, respectively followed by a 60-day recovery period to test the submergence tolerance. The results showed that the survival decreased with the increasing flooding duration. Different submergence duration treatments affected dry mass accumulation and carbohydrate content of roots, stems and leaves. Flooding stress affected the activities of pyruvate decarboxylase (PDC), ethanol dehydrogenase (ADH) and lactic dehydrogenase (LDH) enzymes, which indicated the roots and leaves adapt to long-term flooding by reinforcing their anaerobic respiration and activities of ADH were higher than those of LDH for roots and leaves with stronger alcoholic fermentation mainly. After de-submergence, the recovery patterns of carbohydrate were coincided with those of dry mass accumulation of the roots, stems and leaves. A significant regression equation analysis showed root starch content and dry mass accumulation were the major factors affecting the seedling survival. And D. chinense accumulated substantial amounts of carbohydrate before submergence and invested more in roots and stems than in leaves, which enhances long-term survival under submergence. Carbohydrate storage is a key functional trait that can explain high survival under submergence. D. chinense may have adopted a suite of growth and respiratory metabolic adaptation strategies to survive long-term submergence.

Effect of hypobaric treatment on off-flavour development and energy metabolism in ‘Bruno’ kiwifruit

Kiwifruit (Actinidia deliciosa cv. Bruno) can more easily acquire ‘alcoholic flavour’ due to the accumulation of ethanol under normal ripening conditions compared to the other cultivars of kiwifruit. In this study, the effects of hypobaric treatment (25 ± 5 kPa for 30 min) one time (T1) and two times (T2) on fruit quality, ethanol metabolism and energy metabolism in ‘Bruno’ kiwifruit were investigated during room temperature storage. The results showed that T2 treatment effectively reduced fruit decay and weight loss during the whole storage period, and both T1 and T2 treatments maintained higher values of total phenolic, quinic acid and citric acid than CK during the late stage of storage. Moreover, the hypobaric treatments reduced alcoholic flavour development, while T2 treatment was more effective than T1 treatment. The mechanism for this effect might involve two aspects. On the one hand, T2 treatment enhanced aerobic metabolism by increasing the energy level and the activities of succinic dehydrogenase (SDH), cytochrome c oxidase (CCO) and H+-adenosine triphosphatase (H+-ATPase) during the late stage of storage. On the other hand, T2 treatment inhibited anaerobic metabolism by decreasing the concentrations of acetaldehyde and ethanol and the activities of pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH). In conclusion, we speculated that the effect of hypobaric treatment on ‘Bruno’ kiwifruit might be involved in the regulation of aerobic and anaerobic metabolisms during storage at room temperature.

RICE SEEDLING ESTABLISHMENT AS INFLUENCED BY CULTIVARS AND SEED PRIMING WITH POTASSIUM NITRATE

Poor crop establishment is one of the major constraints to obtain the higher potential of rice, particularly in areas prone to environmental stresses. Therefore, present study was conducted to evaluate the effects of potassium nitrate on germination dynamics, seedling growth and associated physiological and biochemical events of two rice cultivars. For this purpose, various seed priming treatments were tested in lab and greenhouse. The percent concentrations of potassium nitrate were 0.25, 0.50, 0.75, 1.0 and 1.25 in both lab evaluation and greenhouse experiment. Non-primed seeds were maintained as a control for comparison. The results depicted that soaking rice seeds at higher concentrations of KNO3 could delay emergence time and final emergence (%) in both cultivars under lab and greenhouse conditions. Seed priming with 0.75% KNO3 significantly increased the stand establishment and seedling vigor attributes of both cultivars compared with other concentrations and naked rice seeds both in lab evaluation and greenhouse screening. Similarly, highest values for photosynthesis rate, evaporation rate and CO2 index were observed in experimental units receiving primed seeds with 0.75% KNO3 under greenhouse screening. Interestingly, no variance was observed among both rice cultivars. Overall, higher seed emergence, seedling vigor and associated biochemical attributes due to seed priming with 0.75% KNO3 was associated with decrease in alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDH) activities in lab and greenhouse screening.

Comparative transcriptome analysis of genes involved in volatile compound synthesis in blueberries (Vaccinium virgatum) during postharvest storage

• Genes involved in postharvest blueberry aroma biosynthesis were characterized. • Increased ethyl acetate was associated with increased PDC activity after harvest. • Postharvest storage modulated terpene synthase (TPS) genes associated with linalool. Transcriptional regulation of aroma formation genes during postharvest storage remains poorly understood in the blueberry. In order to have a better understanding of the transcriptional regulation processes that occur in rabbiteye blueberry during storage and their effect on the volatile composition change, we performed volatile metabolite profiling and transcriptomic analysis. Our study reveals that during postharvest storage, ‘Garden blue’ blueberry volatile composition changed by regulating several secondary metabolic pathways, in particular, by stimulating the expression of pyruvate decarboxylase (PDC) genes, resulting in a high production of ethyl acetate. Postharvest storage also modulated some terpene synthase (TPS) genes associated with linalool production. The concentration of C6 aldehydes and alcohols decreased during the postharvest storage accompanied by lower lipoxygenase (LOX) gene expression. These findings illustrate the molecular and biochemical mechanisms that occur in blueberry during the postharvest storage period, especially with regard to volatile composition changes.