Endogenous ABA Levels Research Articles

The transcription factor ZmbHLH105 confers cadmium tolerance by promoting abscisic acid biosynthesis in maize

Cadmium (Cd), a highly toxic heavy metal, profoundly impacts crop productivity. The bHLH-type transcription factors regulate plant stress responses, yet their involvement in maize's Cd stress response remains unclear. Here, we studied ZmbHLH105, a maize bHLH gene induced by Cd exposure. Overexpression of ZmbHLH105 in maize seedlings, which were treated with 1.0 mM CdCl2 for 7 days, increased endogenous ABA levels, decreased Cd accumulation, and enhanced Cd stress tolerance. ZmbHLH105 directly bound to promoter regions of two key ABA biosynthesis genes ZmNCED1/2, activating their transcription, thus boosting ABA levels and Cd tolerance. ZmbHLH105-overexpression promoted lignin synthesis, while ZmbHLH105-RNAi attenuated this effect. Exogenous ABA supplementation increased lignin content in Cd-stressed maize roots, suggesting ZmbHLH105-mediated Cd tolerance involves ABA-induced lignin deposition and cell wall thickening. Moreover, Cd transport-related gene expression was suppressed in ZmbHLH105 overexpression lines. Our findings demonstrate that ZmbHLH105 decreases Cd accumulation, improving Cd tolerance by enhancing ABA biosynthesis, increasing lignin deposition, thickening cell walls, and inhibiting Cd absorption in maize roots. This study unveils ZmbHLH105's mechanisms in Cd tolerance, highlighting its potential in breeding low Cd-accumulating crops for food and environment safety.

A mutated algal species of Isochrysis sp. obtained via atmospheric room temperature plasma mutagenesis promoted lipid accumulation through the abscisic acid pathway

Isochrysis sp. is an economically important algae rich in unsaturated fatty acids, but its susceptibility to strain degeneration poses challenges for practical applications. To address this, we used atmospheric room temperature plasma (ARTP) for mutagenesis, creating a stable mutant strain, Yield 8 (Y8), with rapid growth and high lipid content. Transcriptome analysis showed upregulation of genes in genetic information processes and metabolic pathways, with notable upregulation of long-chain fatty acid CoA ligase and acyl-CoA acyltransferase (ACAT), consistent with the trend of fatty acid accumulation. Interestingly, the expression levels of ζ-carotene desaturase (ZDS), zeaxanthin epoxidase (ZEP), and phosphatase 2C (PP2C) were upregulated in the Y8 mutant, indicating activation of the ABA pathway. Further, the increased endogenous ABA levels in Y8, along with a 1.17-fold increase in DHA and a 1.26-fold increase in ω3 fatty acids after exogenous ABA application, suggest that Y8's improved traits are mediated by the ABA pathway. These findings highlight Y8's potential for practical applications and further research.

Genome-Wide Identification of PYL/RCAR ABA Receptors and Functional Analysis of LbPYL10 in Heat Tolerance in Goji (Lycium barbarum).

The characterization of the PYL/RCAR ABA receptors in a great deal of plant species has dramatically advanced the study of ABA functions involved in key physiological processes. However, the genes in this family are still unclear in Lycium (Goji) plants, one of the well-known economically, medicinally, and ecologically valuable fruit crops. In the present work, 12 homologs of Arabidopsis PYL/RCAR ABA receptors were first identified and characterized from Lycium (L.) barbarum (LbPYLs). The quantitative real-time PCR (qRT-PCR) analysis showed that these genes had clear tissue-specific expression patterns, and most of them were transcribed in the root with the largest amount. Among the three subfamilies, while the Group I and Group III members were down-regulated by extraneous ABA, the Group II members were up-regulated. At 42 °C, most transcripts showed a rapid and violent up-regulation response to higher temperature, especially members of Group II. One of the genes in the Group II members, LbPYL10, was further functionally validated by virus-induced gene silencing (VIGS) technology. LbPYL10 positively regulates heat stress tolerance in L. barbarum by alleviating chlorophyll degradation, thus maintaining chlorophyll stability. Integrating the endogenous ABA level increase following heat stress, it may be concluded that LbPYL-mediated ABA signaling plays a vital role in the thermotolerance of L. barbarum plants. Our results highlight the strong potential of LbPYL genes in breeding genetically modified L. barbarum crops that acclimate to climate change.

Melatonin Modulates Tomato Root Morphology by Regulating Key Genes and Endogenous Hormones

Melatonin plays a vital role in plant growth and development. In this study, we treated hydroponically grown tomato roots with various concentrations of exogenous melatonin (0, 10, 30, and 50 μmol·L−1). We utilized root scanning and microscopy to examine alterations in root morphology and cell differentiation and elucidated the mechanism by which melatonin regulates these changes through the interplay with endogenous hormones and relevant genes. The results showed that for melatonin at concentrations ranging between 10 and 30 μmol·L−1, the development of lateral roots were significantly stimulated, the root hair growth was enhanced, and biomass accumulation and root activity were increased. Furthermore, we elucidated that melatonin acts as a mediator for the expression of genes, such as SlCDKA1, SlCYCA3;1, SlARF2, SlF3H, and SlKT1, which are involved in the regulation of root morphology changes. Additionally, we observed that melatonin influences the levels of endogenous hormones, including ZT, GA3, IAA, ABA, and BR, which subsequently impact the root morphology development of tomato roots. In summary, this study shows that tomato root morphology can be promoted by the optimal concentration of exogenous melatonin (10–30 μmol·L−1).

Overexpression of NtDOGL4 improves cadmium tolerance through abscisic acid signaling pathway in tobacco

The DELAY OF GERMINATION1-LIKE (DOGL) genes play an essential role in diverse biological processes in plants. However, their exact involvement in the response to cadmium (Cd) stress via the ABA pathway remains unclear. Here, we focused on NtDOGL4, a tobacco DOGL gene whose expression is highly induced upon exposure to Cd. Overexpression of NtDOGL4 in tobacco resulted in elevated endogenous ABA levels, reduced Cd accumulation, and increased tolerance to Cd. Moreover, NtDOGL4 overexpression led to decreased accumulation of reactive oxygen species (ROS) and improved ROS scavenging capacity under Cd stress. Further analyses revealed the direct binding of the transcription factor ABSCISIC ACID-INSENSITIVE 5 (ABI5) to the NtDOGL4 promoter, positively regulating its expression in tobacco. Notably, NtDOGL4 overexpression promoted suberin formation and deposition, while suppressing the expression of Cd transporter genes in tobacco roots, as evidenced by histochemical staining, suberin fraction determination, and qRT-PCR assays. Collectively, our results demonstrate that NtDOGL4 overexpression reduces Cd accumulation, thereby improving Cd stress tolerance through the modulation of antioxidant system, transcription of Cd transporters, and suberin deposition. Notably, the NtABI5-NtDOGL4 module functions as a positive regulator in tobacco's Cd tolerance, underscoring its potential as a molecular target for developing low-Cd crops to ensure environmental safety.

Tomato plants with different endogenous ABA levels show unique phenotypic and phytohormones response to elevated CO2 and progressive soil drying

Tomato plants with different endogenous ABA levels show unique phenotypic and phytohormones response to elevated CO₂ and progressive soil drying

A bermudagrass variant exhibits strong tolerance to low temperature associated with enhanced sugar metabolism and cold‐responsive pathways

AbstractAs a warm‐season turfgrass, bermudagrass (Cynodon) is sensitive to low ambient temperature. The objectives of this study were to evaluate cold tolerance of a new variant Chuannong‐3 under field condition and to further elucidate metabolic and molecular bases of cold tolerance in the Chuannong‐3 as compared to triploid Tifdwarf (Cynodon transvaalensis × Cynodon dactylon) and tetraploid common bermudagrass 001 (C. dactylon). The Chuannong‐3 was identified as a triploid bermudagrass based on ploidy analysis. Chuannong‐3, Tifdwarf, or common bermudagrass 001 exhibited different tolerance to low temperature in field (Chuannong‐3 > common bermudagrass 001 > Tifdwarf). The Chuannong‐3 maintained significantly lower oxidative damage to cell membrane system, chlorophyll loss, and inhibition of photochemical efficiency as well as higher water‐soluble carbohydrate content than Tifdwarf or common bermudagrass 001 in winter of 2022 and 2021. Further study found that Chunanong‐3 exhibited the highest glucose, fructose, sucrose, raffinose content, raffinose synthase activity, and CdSPS1 expression as compared to Tifdwarf and common bermudagrass 001, which provided potential protection against chilling and freezing damages. Chilling and freezing stresses significantly up‐regulated ABA‐dependent (endogenous ABA level, CdABF1, CdDHN4, and CdLEA3) and ABA‐independent (CdWRKY2, CdCBF1, and CdCOR440) pathways in three bermudagrasses, but the most pronounced effects were detected in the Chuannong‐3. These findings indicated that Chuannong‐3 had better ability to acclimate to low temperature stress in relation to up‐regulation of sugar accumulation and metabolism, ABA signaling, and CBF‐COR pathway. This new variant Chuannong‐3 could be a valuable bermudagrass grown in temperate and transition zones.

Transcription factor ANAC004 enhances Cd tolerance in Arabidopsis thaliana by regulating cell wall fixation, translocation and vacuolar detoxification of Cd, ABA accumulation and antioxidant capacity

Cadmium (Cd) is toxic to plants, which have evolved multiple strategies to cope with Cd stress. In this study, we identified a nucleus-localized NAC-type transcription factor, ANAC004, which is induced by Cd and involved in regulating Cd resistance in Arabidopsis. First, anac004 mutants exhibited Cd sensitive phenotype and accumulated more Cd (12–23% higher than wild type in roots and shoots); plants overexpressing ANAC004 showed the opposite phenotype and with lower Cd accumulation. Second, ANAC004 enhanced Cd fixation in cell wall hemicellulose, thus reducing Cd2+ influx into root cells. Third, ANAC004 was involved in the process of vacuolar Cd compartmentalization by regulating the genes associated with Cd detoxification (PCS1/2, NAS4, ABCC1/2/3, MTP1/3, IREG2 and NRAMP3/4). Fourth, ANAC004 reduced root-to-shoot Cd translocation through down-regulated Cd translocation-related genes (HMA2 and HMA4). Finally, the expression of genes related to ABA synthesis (AAO3, MCSU, and NCED3) and the activities of antioxidant enzymes (SOD, POD and CAT) were all reduced in anac004 mutants, leading to reduced levels of endogenous ABA and increased accumulation of reactive oxygen species (O2.− and H2O2) and MDA, which ultimately weakened resistance to Cd. Our results suggest that ANAC004 decreases Cd accumulation in Arabidopsis through enhancing cell wall Cd immobilization, increasing vacuolar Cd detoxification, and inhibiting Cd translocation, thus improving Cd resistance, processes that might be mediated by ABA signaling and antioxidant defense systems.

OsHIPL1, a hedgehog-interacting protein-like 1 protein, increases seed vigour in rice.

SummaryThe cultivation of rice varieties with high seed vigour is vital for the direct seeding of rice, and the molecular basis of regulation of seed vigour remains elusive. Here, we cloned a new gene OsHIPL1, which encodes hedgehog‐interacting protein‐like 1 protein as a causal gene of the major QTL qSV3 for rice seed vigour. OsHIPL1 was mainly localized in the plasma membrane and nucleus. RNA sequencing (RNA‐seq) revealed that the ABA‐related genes were involved in the OsHIPL1 regulation of seed vigour in rice. The higher levels of endogenous ABA were measured in germinating seeds of OsHIPL1 mutants and NIL‐qsv3 line compared to IR26 plants, with two up‐regulated ABA biosynthesis genes (OsZEP and OsNCED4) and one down‐regulated ABA catabolism gene OsABA8ox3. The expression of abscisic acid‐insensitive 3 (OsABI3), OsABI4 and OsABI5 was significantly up‐regulated in germinating seeds of OsHIPL1 mutants and NIL‐qsv3 line compared to IR26 plants. These results indicate that the regulation of seed vigour of OsHIPL1 may be through modulating endogenous ABA levels and altering OsABIs expression during seed germination in rice. Meanwhile, we found that OsHIPL1 interacted with the aquaporin OsPIP1;1, then affected water uptake to promote rice seed germination. Based on analysis of single‐nucleotide polymorphism data of rice accessions, we identified a Hap1 haplotype of OsHIPL1 that was positively correlated with seed germination. Our findings showed novel insights into the molecular mechanism of OsHIPL1 on seed vigour.

Beta-Amylase and Phosphatidic Acid Involved in Recalcitrant Seed Germination of Chinese Chestnut.

Chinese chestnut (Castanea mollissima), a species with recalcitrant seeds, is an important source of nuts and forest ecosystem services. The germination rate of recalcitrant seeds is low in natural habitats and decreases under conditions of desiccation and low temperature. The germination rate of cultivated Chinese chestnut seeds is significantly higher than that of wild seeds. To explore the reasons for the higher germination rate of cultivated seeds in Chinese chestnut, 113,524 structural variants (SVs) between the wild and cultivated Chinese chestnut genomes were detected through genome comparison. Genotyping these SVs in 60 Chinese chestnut accessions identified allele frequency changes during Chinese chestnut domestication, and some SVs are overlapping genes for controlling seed germination. Transcriptome analysis revealed downregulation of the abscisic acid synthesis genes and upregulation of the beta-amylase synthesis genes in strongly selected genes of cultivated seeds. On the other hand, hormone and enzyme activity assays indicated a decrease in endogenous ABA level and an increase in beta-amylase activity in cultivated seeds. These results shed light on the higher germination rate of cultivated seeds. Moreover, phosphatidic acid synthesis genes are highly expressed in seed germination stages of wild Chinese chestnut and may play a role in recalcitrant seed germination. These findings provide new insight into the regulation of wild seed germination and promote natural regeneration and succession in forest ecosystems.

A Comprehensive Evaluation of Salt Tolerance in Tomato (Var. Ailsa Craig): Responses of Physiological and Transcriptional Changes in RBOH's and ABA Biosynthesis and Signalling Genes.

Salinity is a ubiquitous stressor, depleting osmotic potential and affecting the tomato seedlings’ development and productivity. Considering this critical concern, we explored the salinity response in tomato seedlings by evaluating them under progressive salt stress duration (0, 3, 6, and 12 days). Intriguingly, besides the adverse effect of salt stress on tomato growth the findings exhibited a significant role of tomato antioxidative system, RBOH genes, ABA biosynthesis, and signaling transcription factor for establishing tolerance to salinity stress. For instance, the activities of enzymatic and non-enzymatic antioxidants continued to incline positively with the increased levels of reactive oxygen species (O2•−, H2O2), MDA, and cellular damage, suggesting the scavenging capacity of tomato seedlings against salt stress. Notably, the RBOH transcription factors activated the hydrogen peroxide-mediated signalling pathway that induced the detoxification mechanisms in tomato seedlings. Consequently, the increased gene expression of antioxidant enzymes and the corresponding ratio of non-enzymatic antioxidants AsA-GSH suggested the modulation of antioxidants to survive the salt-induced oxidative stress. In addition, the endogenous ABA level was enhanced under salinity stress, indicating higher ABA biosynthesis and signalling gene expression. Subsequently, the upregulated transcript abundance of ABA biosynthesis and signalling-related genes suggested the ABA-mediated capacity of tomato seedlings to regulate homeostasis under salt stress. The current findings have revealed fascinating responses of the tomato to survive the salt stress periods, in order to improve the abiotic stress tolerance in tomato.

The Rice Abscisic Acid-Responsive RING Finger E3 Ligase OsRF1 Targets OsPP2C09 for Degradation and Confers Drought and Salinity Tolerance in Rice.

Drought and salinity are major important factors that restrain growth and productivity of rice. In plants, many really interesting new gene (RING) finger proteins have been reported to enhance drought and salt tolerance. However, their mode of action and interacting substrates are largely unknown. Here, we identified a new small RING-H2 type E3 ligase OsRF1, which is involved in the ABA and stress responses of rice. OsRF1 transcripts were highly induced by ABA, salt, or drought treatment. Upregulation of OsRF1 in transgenic rice conferred drought and salt tolerance and increased endogenous ABA levels. Consistent with this, faster transcriptional activation of key ABA biosynthetic genes, ZEP, NCED3, and ABA4, was observed in OsRF1-OE plants compared with wild type in response to drought stress. Yeast two-hybrid assay, BiFC, and co-immunoprecipitation analysis identified clade A PP2C proteins as direct interacting partners with OsRF1. In vitro ubiquitination assay indicated that OsRF1 exhibited E3 ligase activity, and that it targeted OsPP2C09 protein for ubiquitination and degradation. Cell-free degradation assay further showed that the OsPP2C09 protein is more rapidly degraded by ABA in the OsRF1-OE rice than in the wild type. The combined results suggested that OsRF1 is a positive player of stress responses by modulating protein stability of clade A PP2C proteins, negative regulators of ABA signaling.

Molecular and Physiological Perspectives of Abscisic Acid Mediated Drought Adjustment Strategies.

Drought is the most prevalent unfavorable condition that impairs plant growth and development by altering morphological, physiological, and biochemical functions, thereby impeding plant biomass production. To survive the adverse effects, water limiting condition triggers a sophisticated adjustment mechanism orchestrated mainly by hormones that directly protect plants via the stimulation of several signaling cascades. Predominantly, water deficit signals cause the increase in the level of endogenous ABA, which elicits signaling pathways involving transcription factors that enhance resistance mechanisms to combat drought-stimulated damage in plants. These responses mainly include stomatal closure, seed dormancy, cuticular wax deposition, leaf senescence, and alteration of the shoot and root growth. Unraveling how plants adjust to drought could provide valuable information, and a comprehensive understanding of the resistance mechanisms will help researchers design ways to improve crop performance under water limiting conditions. This review deals with the past and recent updates of ABA-mediated molecular mechanisms that plants can implement to cope with the challenges of drought stress.

Combined effect of partial root drying and elevated atmospheric CO2 on the physiology and fruit quality of two genotypes of tomato plants with contrasting endogenous ABA levels

Elevated CO2 concentration (e[CO2]) could induce the decline of nutrient concentration in tomato fruit, although it enhances the yield. Alternate partial root drying (PRD) irrigation is a water-saving irrigation strategy, which may enhance tomato fruit quality including both organic and inorganic attributes. Yet, it remains unknown whether PRD could alleviate the negative impact of e[CO2] on the quality attributes of tomato fruit. To investigate that, two genotypes of tomato plants differing in their endogenous abscisic acid level, i.e. Ailsa Craig (wild type, WT) and its correspondent ABA-deficient mutant (flacca), were grown in ambient CO2 (a[CO2], 400 ppm) and e[CO2] (800 ppm) environment, respectively. And three irrigation regimes including full irrigation (FI), deficit irrigation (DI) and PRD were applied during anthesis to fruit ripping stages. The results showed that e[CO2] increased net photosynthetic rate, decreased stomatal conductance and transpiration rate. Tomato yield was more sensitive to irrigation regimes than [CO2], and the reduction of fruit yield caused by PRD was attenuated under e[CO2], especially in flacca. Both e[CO2] and PRD enhanced water use efficiency. The concentration of total soluble solid, total sugar and total acid, as well as fruit firmness were improved in PRD. A negative effect of e[CO2] on fruit mineral nutrition was seen only in flacca, and as expected, such impact was attenuated by the reduced irrigation regimes (DI and PRD). Collectively, it is suggested that the responses of tomato fruit quality to e[CO2] and reduced irrigation regimes are genotypic-dependent, where the endogenous ABA level of the plants plays an important role, and this must be considered in climate management in greenhouse tomato cultivation.

Source-Sink Manipulation Affects Accumulation of Zinc and Other Nutrient Elements in Wheat Grains.

To better understand the source–sink flow and its relationships with zinc (Zn) and other nutrients in wheat (Triticum aestivum L.) plants for biofortification and improving grain nutritional quality, the effects of reducing the photoassimilate source (through the flag leaf removal and spike shading) or sink (through the removal of all spikelets from one side of the spike, i.e., 50% spikelets removal) in the field of the accumulation of Zn and other nutrients in grains of two wheat cultivars (Jimai 22 and Jimai 44) were investigated at two soil Zn application levels. The kernel number per spike (KNPS), single panicle weight (SPW), thousand kernel weight (TKW), total grain weight (TGW) sampled, concentrations and yields of various nutrient elements including Zn, iron (Fe), manganese (Mn), copper (Cu), nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg), phytate phosphorus (phytate-P), phytic acid (PA) and phytohormones (ABA: abscisic acid, and the ethylene precursor ACC: 1-aminocylopropane-1-carboxylic acid), and carbon/N ratios were determined. Soil Zn application significantly increased the concentrations of grain Zn, N and K. Cultivars showing higher grain yields had lower grain protein and micronutrient nutritional quality. SPW, KNPS, TKW (with the exception of TKW in the removal of half of the spikelets), TGW, and nutrient yields in wheat grains were most severely reduced by half spikelet removal, secondly by spike shading, and slightly by flag leaf removal. Grain concentrations of Zn, N and Mg consistently showed negative correlations with SPW, KNPS and TGW, but positive correlations with TKW. There were general positive correlations among grain concentrations of Zn, Fe, Mn, Cu, N and Mg, and the bioavailability of Zn and Fe (estimated by molar ratios of PA/Zn, PA/Fe, PA × Ca/Zn, or PA × Ca/Fe). Although Zn and Fe concentrations were increased and Ca was decreased in treatments of half spikelet removal and spike shading, the treatments simultaneously increased PA and limited the increase in bioavailability of Zn and Fe. In general, different nutrient elements interact with each other and are affected to different degrees by source–sink manipulation. Elevated endogenous ABA levels and ABA/ACC ratios were associated with increased TKW and grain-filling of Zn, Mn, Ca and Mg, and inhibited K in wheat grains. However, the effects of ACC were diametrically opposite. These results provide a basis for wheat grain biofortification to alleviate human malnutrition.

Halotolerant bacteria mitigate the effects of salinity stress on soybean growth by regulating secondary metabolites and molecular responses

BackgroundSalinity is a major threat to the agriculture industry due to the negative impact of salinity stress on crop productivity. In the present study, we isolated rhizobacteria and evaluated their capacities to promote crop growth under salt stress conditions.ResultsWe isolated rhizospheric bacteria from sand dune flora of Pohang beach, Korea, and screened them for plant growth-promoting (PGP) traits. Among 55 bacterial isolates, 14 produced indole-3-acetic acid (IAA), 10 produced siderophores, and 12 produced extracellular polymeric and phosphate solubilization. Based on these PGP traits, we selected 11 isolates to assess for salinity tolerance. Among them, ALT29 and ALT43 showed the highest tolerance to salinity stress. Next, we tested the culture filtrate of isolates ALT29 and ALT43 for IAA and organic acids to confirm the presence of these PGP products. To investigate the effects of ALT29 and ALT43 on salt tolerance in soybean, we grew seedlings in 0 mM, 80 mM, 160 mM, and 240 mM NaCl treatments, inoculating half with the bacterial isolates. Inoculation with ALT29 and ALT43 significantly increased shoot length (13%), root length (21%), shoot fresh and dry weight (44 and 35%), root fresh and dry weight (9%), chlorophyll content (16–24%), Chl a (8–43%), Chl b (13–46%), and carotenoid (14–39%) content of soybean grown under salt stress. Inoculation with ALT29 and ALT43 also significantly decreased endogenous ABA levels (0.77-fold) and increased endogenous SA contents (6–16%), increased total protein (10–20%) and glutathione contents, and reduced lipid peroxidation (0.8–5-fold), superoxide anion (21–68%), peroxidase (12.14–17.97%), and polyphenol oxidase (11.76–27.06%) contents in soybean under salinity stress. In addition, soybean treated with ALT29 and ALT43 exhibited higher K+ uptake (9.34–67.03%) and reduced Na+ content (2–4.5-fold). Genes involved in salt tolerance, GmFLD19 and GmNARK, were upregulated under NaCl stress; however, significant decreases in GmFLD19 (3–12-fold) and GmNARK (1.8–3.7-fold) expression were observed in bacterial inoculated plants.ConclusionIn conclusion, bacterial isolates ALT29 and ALT43 can mitigate salinity stress and increase plant growth, providing an eco-friendly approach for addressing saline conditions in agricultural production systems.

Removal of superior wheat kernels promotes filling of inferior kernels by changing carbohydrate metabolism and sink strength

Poor filling and low weight of inferior kernels limit the further improvement of wheat yield. Two cultivars, Shuangda 1 and Xinong 538, with different grain weights, were selected to investigate the physiological changes of inferior kernels by removal of superior kernels (RS) at the flowering stage. iTRAQ combined with physiological indexes was used to identify factors limiting the filling of inferior kernels. Removal of superior kernels significantly increased the mean filling rate of inferior kernels and thus increased their weight. A set of 6012 proteins in inferior wheat kernels were differentially expressed between the RS and control. These differentially expressed proteins were involved mainly in carbon metabolism and energy metabolism. The main reason for the promoting effect of RS on the filling of inferior kernels may be that RS downregulated proteins involved in glycolysis and pyruvate metabolism while upregulating proteins involved in carbon fixation and photosynthesis. Consequently, RS greatly increased the ATP content in inferior kernels, supplying energy for them to absorb photosynthetic assimilates. Removal of superior kernels increased the activities of sucrose synthase, soluble starch synthase, adenosine diphosphate glucose pyrophosphorylase, and starch branching enzyme in inferior kernels and promoted starch accumulation in them. Thus, RS promoted the filling of inferior kernels and increased their weight. The promoting effect of RS on starch synthesis in inferior kernels was associated with their endogenous IAA and ABA levels.

Comparative analysis of the gene expression profile under two cultivation methods reveals the critical role of ABA in grape quality promotion

Root restriction is a critical cultivation technique that accelerates ripening and improves fruit quality, by a still unknown mechanism. ABA is an important phytohormone in both ripening and stress responses. To elucidate the relationship between ABA content and root restriction-induced fruit quality promotion, the endogenous ABA level was investigated in five-year-old ‘Muscat Hamburg’ grapevines from the pre-anthesis stage to maturity. The results showed that ABA production was significantly enhanced by root restriction. A transcriptomics-based approach was taken to identify transcriptionally regulated genes associated with ABA biosynthesis, catabolism and signal transduction in the four development periods of grape. A total of 2873 (884 upregulated and 1989 downregulated) DEGs were identified in all stages. Those related to metabolic processes, cellular processes, responses to stimuli, biological regulation and signal transduction were abundant in the biological process GO category. KEGG analysis revealed that plant hormone signal transduction and carotenoid biosynthesis were enriched out of the 127 total pathways. 12 DEGs involved in ABA biosynthesis and catabolism and 69 DEGs involved in plant hormone signal transduction were significantly regulated by root restriction. Twelve DEGs related to the biosynthesis and catabolism of ABA or plant hormone signal transduction were selected to validate the data obtained by RNA-Seq, and the results showed that genes such as PP2C, NCED, AAO3, ABA3, and CYP707A1, involved in ABA biosynthesis and signal transduction, may play important roles in the promotion of fruit quality by root restriction. This study suggests a potential ABA-mediated mechanism by which root-restriction cultivation promotes fruit ripening.

Foliar applied 24-epibrassinolide alleviates salt stress in rice (Oryza sativa L.) by suppression of ABA levels and upregulation of secondary metabolites

ABSTRACT Salt stress hinders plant growth and disrupts many physio-biochemical and molecular processes. The present study evaluated the potential role of foliar applied 24-epibrassinolide (EBR) for mitigating the adverse effects of salinity in rice plants. Our findings showed that salt stress reduced several growth and physiological parameters, and substantially increased oxidative stress in rice seedlings. The foliar application of EBR replenished the negative effects of salt stress by improving plant growth and physiological attributes in rice plants. Moreover, application of EBR substantially reduced oxidative injuries by enhancing antioxidant enzymes and phenolic compounds in rice plants during salt stress. Interestingly, the endogenous ABA levels were declined in stressed plants by EBR treatment, also validated by expression analysis of ABA-related genes. In addition, application of EBR upregulated carotenoids and flavonoids pathway genes, thus showing its function to activate secondary metabolism in rice plants during salt stress. The principal component analysis (PCA) indicated that, under salt stress, the response of EBR-treated rice plants was strongly correlated with the accumulation of phenolic compounds and flavonoids. Collectively, this study presents useful insight into the distinct role of EBR by activating underlying enzymatic and non-enzymatic defense mechanisms to mitigate salinity in rice plants.

HaASR1 gene cloned from a desert shrub, Haloxylon ammodendron, confers drought tolerance in transgenic Arabidopsis thaliana

Abiotic stresses pose adverse impact on plant growth and development and exploring the stress tolerance genes from dominant species is still urgent. The desert shrub, Haloxylon ammodendron, a C4 and succulent xero-halophyte species, has great drought and salt tolerance. Here, we reported the isolation and functions analysis of HaASR1 (abscisic acid, stress, and ripening) from H. ammodendron. HaASR1 interacts with HaPrxQ and HaBADH and may function in preventing PrxQ and BADH from denaturation in plants under drought stress. Overexpression of HaASR1 reduces the sensitivity of Arabidopsis plants to exogenous ABA and decreases the endogenous ABA level through down-regulating ABA biosynthesis genes under drought stress, which making the plants display less inhibition of shoot growth and enhanced drought tolerance. Overexpression of HaASR1 significantly enhances photosynthetic capacity of Arabidopsis plants under drought stress by reducing H2O2 accumulation through up-regulating AtCAT2, AtAPX1 and AtPrxQ and maintaining relatively integrity of chloroplasts. Overexpression of HaASR1 also significantly improves water-retaining ability. Taken together, we propose that HaASR1 plays critical roles in plant drought stress adaptation by making the plants partially defective in ABA signaling and participating in drought tolerance regulation through nonstomatal pathways, enhancing ROS-scavenging ability and water-retaining ability, which is different from the functions of previously reported ASR genes from other plant species. This research also reveals that HaASR1 gene from the desert shrub, Haloxylon ammodendron, has potential application values in improving abiotic stresses of other plant species by genetic engineering.