Exogenous Application Of Abscisic Acid Research Articles

Higher endogenous abscisic acid confers greater tolerance to saline-alkaline stress in Petunia hybrida

Saline-alkaline stress not only leads to reduced crop yields but also diminishes the ornamental value of flowers. While petunia exhibits tolerance to saline-alkaline stress, research on the mechanisms underlying this tolerance remains unreported. We investigated the physiological and molecular mechanisms underlying saline-alkaline stress tolerance using two petunia genotypes (Haishishenlou and Mitchell Diploid) with differing tolerance levels. Haishishenlou exhibited less inhibition of growth under saline-alkaline stress compared to Mitchell Diploid, as indicated by higher biomass. Higher endogenous concentration of abscisic acid (ABA) and greater expression levels of ABA biosynthetic genes and lower expression levels of ABA catabolic genes in Haishishenlou than in Mitchell Diploid were observed when challenged by saline-alkaline stress, suggesting that a higher concentration of ABA may underpin the greater tolerance of Haishishenlou to saline-alkaline stress than that of Mitchell Diploid. Under saline-alkaline conditions, Haishishenlou displayed higher chlorophyll content, photosynthetic rates, Pro and soluble sugars content, as well as higher activities of catalase (CAT), superoxide dismutase (SOD) and peroxidase (POD), and a lower Na+/K+ ratio. Exogenous application of ABA alleviated the growth inhibition induced by saline-alkaline stress, promoted the accumulation of proline and soluble sugar, reduced reactive oxygen species (ROS) content and Na+/K+ ratio, and improved antioxidative capacity. These results indicated that a higher endogenous concentration of ABA may underpin the greater tolerance of petunia seedlings to saline-alkaline stress, and exogenous ABA improves the saline-alkaline tolerance of petunia seedlings.

Competitive control of CsNCED1-1 by CsLOB1 and CsbZIP40 triggers susceptibility to citrus canker.

Pustule formation is pivotal for the development of the Xanthomonas citri subsp. citri (Xcc)-induced citrus canker disease (CCD). Although our previous study demonstrated that the exogenous application of abscisic acid (ABA) facilitated pustule formation induced by Xcc, the precise mechanism remains elusive. The 9-cis-epoxycarotenoid dioxygenase (NCED) is a crucial enzyme in ABA biosynthesis. This study explored the role of citrus CsNCED1-1 in CCD resistance through overexpression and RNA interference of CsNCED1-1 in Wanjincheng orange (Citrus sinensis). Our findings indicated that CsNCED1-1 negatively modulated CCD resistance by fostering ABA accumulation, concomitant with an increase in jasmonic acid (JA) and a decrease in salicylic acid (SA). Plants overexpressing CsNCED1-1 displayed shortened leaves with smaller and denser stomata along with irregular and increased palisade cells. CsLOB1 is a known susceptibility gene for CCD, and CsbZIP40 positively influences resistance to this disease. We further confirmed that CsLOB1 promoted and CsbZIP40 suppressed the transcription of CsNCED1-1 by directly binding to the CsNCED1-1 promoter. Notably, CsbZIP40 and CsLOB1 showed a competitive relationship in the regulation of CsNCED1-1 expression, with CsbZIP40 exhibiting greater competitiveness. Overall, our findings highlight that CsNCED1-1 promotes susceptibility to citrus canker by disrupting JA- and SA-mediated defense mechanisms and triggering the proliferation and remodeling of palisade cells, thereby facilitating pathogen colonization and pustule formation. This study offers novel insights into the regulatory mechanisms underlying citrus canker resistance and the role of CsNCED1-1 in citrus.

ABA deficiency and its impact on ion and metabolite profiles in tomato roots under single and combined stress conditions

Abscisic acid (ABA) plays a crucial role in the stress response of plants. Although the impact of ABA on individual stresses has been extensively studied, there is less research on its role in plants grown under stress combination, such as salinity and high temperature. This study analyzes the response at the ionomic and metabolomic levels of tomato roots to ABA deficiency under single salinity or heat stress, as well as under the combination of both stresses, using ABA-deficient (flacca, flc) tomato plants. ABA was found to be crucial in ionic regulation, particularly for Na, K, Ca, and other ions such as Cu, Mn, Zn, Mo, and Fe. However, its influence depended on the type of stress applied, indicating the complexity of plant responses to these adverse environmental factors. In our study, phenylpropanoids, terpenoids, and nitrogenous compounds were the metabolites most affected by endogenous ABA concentration and environmental treatment. On the other hand, the application of exogenous ABA to flc mutants did not fully restore root dry weight, although it did cause significant changes at the ionomic and metabolomic levels. Salinity and heat applied in combination aggravated the vulnerability of flc mutants compared to single stresses, making the application of exogenous ABA more effective under single stresses than under the combined stresses. Finally, a correlation analysis between the ionome and metabolome revealed that the accumulation or deficiency of some ions (i.e., Na, Zn, and Fe) was correlated with the abundance of important metabolites related to amino acid biosynthesis and terpenoid metabolism, among others.

Multi-Omics Exploration of ABA Involvement in Identifying Unique Molecular Markers for Single and Combined Stresses in tomato plants.

Over the past decade, our research group has found that plant responses to combined abiotic stresses are unique and cannot be inferred from studying plants exposed to individual stresses. Understanding how adaptative plant mechanisms integrate from stress perception to biochemical and physiological adjustments is a major challenge in abiotic stress signaling studies. Considering abscisic acid (ABA) as a key regulator in plant abiotic stress responses, in our study, ABA-deficient plants (flc) exposed to single or combined salinity and heat stresses were evaluated and different -omics analyses were conducted. Significant changes in biomass, photosynthesis, ions, transcripts, and metabolites occurred in mutant plants under single or combined stresses. Exogenous ABA application in flc mutants did not fully recover plant phenotypes or metabolic levels but induced cellular reprogramming with changes in specific markers. Multi-omics analysis aimed to identify ABA-dependent, ABA-independent, or stress-dependent markers in plant responses to single or combined stresses. We demonstrated that studying different -omics as a whole led to the identification of specific markers for each stress condition that were not detectable when each -omic was studied individually. This resource article provides an important and novel reference for scientists working in the field of plant abiotic stress. Future exploration of the transcriptomic, ionomic and metabolomic data presented in this study could lead to the identification of new pathways and genes associated with ABA signaling processes. These findings may be utilized to enhance crop resilience to heat waves, salinity, and their combination, contributing to addressing food security challenges in a climate change scenario.

OsABA3 is Crucial for Plant Survival and Resistance to Multiple Stresses in Rice

Preharvest sprouting (PHS) is a serious problem in rice production as it leads to reductions in grain yield and quality. However, the underlying mechanism of PHS in rice remains unclear. In this study, we identified and characterized a preharvest sprouting and seedling lethal (phssl) mutant. The heterozygous phssl/+ mutant exhibited normal plant development, but severe PHS in paddy fields. However, the homozygous phssl mutant was seedling lethal. Gene cloning and genetic analysis revealed that a point mutation in OsABA3 was responsible for the mutant phenotypes. OsABA3 encodes a molybdenum cofactor (Moco) sulfurase. The activities of the sulfureted Moco-dependent enzymes such as aldehyde oxidase (AO) and xanthine dehydrogenase (XDH) were barely detectable in the phssl mutant. As the final step of abscisic acid (ABA) de novo biosynthesis is catalyzed by AO, it indicated that ABA biosynthesis was interrupted in the phssl mutant. Exogenous application of ABA almost recovered seed dormancy of the phssl mutant. The knock-out (ko) mutants of OsABA3 generated by CRISPR-Cas9 assay, were also seedling lethal, and the heterozygous mutants were similar to the phssl/+ mutant showing reduced seed dormancy and severe PHS in paddy fields. In contrast, the OsABA3 overexpressing (OE) plants displayed a significant increase in seed dormancy and enhanced plant resistance to PHS. The AO and XDH activities were abolished in the ko mutants, whereas they were increased in the OE plants. Notably, the Moco-dependent enzymes including nitrate reductase (NR) and sulfite oxidase (SO) showed reduced activities in the OE plants. Moreover, the OE plants exhibited enhanced resistances to osmotic stress and bacterial blight, and flowered earlier without any reduction in grain yield. Taken together, this study uncovered the crucial functions of OsABA3 in Moco sulfuration, plant development, and stress resistance, and suggested that OsABA3 is a promising target gene for rice breeding.

Effect of exogenous abscisic acid on improving low-phosphorus (P) response in rice (Oryza sativa L.)

Phosphorus (P) deficiency is a major constraint to rice productivity worldwide. Exogenous application of abscisic acid (ABA) has not been reported to improve rice response toward P-deficiency. Present study analyzed the biochemical response in the shoots and roots of two rice cultivars, CSR10 (low-P tolerant) and Pusa44 (low-P susceptible) at 36, 72 and 216 h after normal P (NP) (10 ppm) (control), low P (LP) (1 ppm), and LP + ABA given to 12-d old seedlings. Results found that biomass and P-uptake reduced in Pusa44 compared to CSR10 under LP but improved significantly under LP + ABA. P-fractionation was utilized efficiently by CSR10 under LP while LP + ABA improved P-fractionation in both cultivars. LP + ABA improved acid phosphatases in both cultivars. Hexose and sucrose levels were depleted while starch hydrolyzed poorly in Pusa44 compared to CSR10 under LP while LP + ABA enhanced starch hydrolysis and levels of sugars in both cultivars. Starch increased at a late stage in the roots of CSR10 under LP while Pusa44 improved it under LP + ABA. Antioxidant capacity was low while H2O2 was high at early stage in Pusa44 compared to CSR10 under LP. LP + ABA improved antioxidant capacity and reduced H2O2 in both cultivars. Results concluded that ABA is a versatile regulator of not only P-acquisition/P-utilization but also carbohydrates and antioxidant activities under P-deficiency, and exogenous ABA improved low-P tolerance in rice.

Dynamic Changes of Phytohormone Concentrations during <i>Prunella vulgaris</i> L. Development and Impact of Rosmarinic Acid Accumulation through Exogenous ABA Application

Background: Plant hormones not only participate in regulating the growth and development process of plants, but also play an important regulatory role in the synthesis of secondary metabolites. Prunella vulgaris L. (P. vulgaris) is a perennial herb that has a long history for use as a kind of medicinal and edible plant. In order to understand the relationship between plant hormones and Prunella vulgaris L. (P. vulgaris) development. Methods: The quantification of indoleacetic acid (IAA), salicylic acid (SA), jasmonates (JAs), abscisic acid (ABA), 1-aminocyclopropane-1-carboxylic acid (ACC) and cytokinins (CKs) of P. vulgaris during development was performed by a liquid chromatography-mass spectrometry (LC-MS). Furthermore, the effect of exogenous ABA on rosmarinic acid (RA) accumulation was verified. Results: Nuts formation was related to the concentrations of IAA, ABA and ACC in the green-fruit stage, and IAA and ABA levels increased rapidly in this stage. High IAA concentrations can promote an increase in ACC. SA, JAs, ethylene (ET) and ABA were related to the defence response of plants to pathogens. SA concentrations increased sharply after the turning stage, while the concentration of JAs, which are antagonistic to SA, was low. The decrease in ABA concentration after this period may be related to the antagonistic effect of IAA or SA. The CKs trans-zeatin (tZ) and trans-zeatin riboside (tZR) promoted the growth and development of early P. vulgaris, and their concentrations decreased in the late period, leading to withering and senescence of P. vulgaris. The CKs cis-zeatin (cZ) and N6-(2-isopentenyl) adenine (iP) were presumed to be present in nuts. After elicitation with 10 μg/mL ABA, an increase of RA content was observed (p < 0.05). Conclusion: This study can provide an improved basis for elucidating the growth and development mechanism of P. vulgaris in the future, as well as a better understand of the effects of ABA application on RA accumulations.

Identification of miRNAs Interacting with Abscisic Acid to Regulate Fatty Acid Metabolism

Fatty acids are synthesized and stored in seeds during development in Brassica napus. Understanding the molecular mechanism behind fatty acid biosynthesis during seed development is a crucial research objective. In this study, we proved that exogenous application of abscisic acid (ABA) to the siliques can efficiently improve unsaturated fatty acid content in rapeseeds. Then we identified a total of 97 novel microRNAs (miRNAs) and 211 known miRNAs in the seeds of B. napus by high-throughput sequencing. Among them, a total of 23 differentially expressed miRNAs were observed between siliques treated with ABA and the control group. These 23 miRNAs regulated target genes that were involved in lipid metabolism through the integration of gene ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) annotations. Moreover, we validated selected members from these miRNAs and their predicted targets through quantitative RT-PCR. Among these, miR172a, miR395a, and novel13 were significantly down-regulated after ABA treatment, while novel3 was significantly up-regulated. Notably, the predicted target genes of miR172a and miR395a, namely, KAS I and DGAT, play crucial roles in fatty acid synthesis and exhibit up-regulated expression in response to ABA. Our findings suggest that a variety of miRNAs interact with ABA to regulate fatty acid biosynthesis, highlighting the important roles played by miRNAs in the process of fatty acid biosynthesis during seed development.

ABA-receptor agonist iSB09 decreases soil water consumption and increases tomato CO2 assimilation and water use efficiency under drought stress

Climate change can alter precipitation patterns, disrupting the natural water cycle and generating drought periods that negatively impact crop yield or plant survival. Novel biotechnological approaches are being developed to face water deficits. Specifically, molecular knowledge of the plant hormone abscisic acid (ABA) can be harnessed to develop genetic and chemical approaches to cope with abiotic stress. ABA receptor agonists are promising molecules that activate ABA signaling on demand and show long-lasting effects, in contrast to the exogenous application of ABA, which has a short half-life. In this work, we studied the effect of the iSB09 agonist on tomato plants grown under drought stress or well-watered conditions. iSB09 treatment induced stomatal closure in tomato through activation of PYL1-like and PYL4-like ABA receptors. Additionally, RNA-seq analyses reveal coordinated upregulation by ABA or iSB09 of the genes encoding enzymes involved in the synthesis of the osmoprotective galactinol and raffinose family of oligosaccharides. Foliar spraying of iSB09 under drought conditions anticipated the regulation of transpiration, promoted drought avoidance and increased water use efficiency in tomato plants. Physiological analysis of agonist-treated plants reveals increased CO2 assimilation and effective quantum yield of the photosystem II under drought conditions in iSB09-treated plants compared to mock-treated. Faster regulation of transpiration at the start of the drought period was achieved by iSB09 treatment, and, as a result, water consumption was reduced compared to mock-treated plants. Overall, the agonist treatment mounts the genome-wide transcriptional response to stress and increases water use efficiency under drought conditions and plant protection.

Abscisic acid enhances alkaline stress tolerance in grapevines: Physiological and transcriptional profiling

Abscisic acid (ABA) is a crucial signaling regulator governing plant growth and survival during adverse conditions. However, the mechanism by which ABA mediates grapevine tolerance to alkali stress has not yet been elucidated. Here, we investigated the role of ABA in regulating physiological characteristics and transcriptome of grapevines under alkali stress through the application of exogenous ABA and fluridone (an ABA biosynthesis inhibitor). The results revealed that alkali stress led to significant reductions in the net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO2 concentration (Ci), transpiration rate (Tr), chlorophyll content, the maximum quantum yields of primary photochemistry of PSII (Fv/Fm), nonphotochemical quenching (NPQ), which were greatly alleviated by exogenous ABA (50 and 100 μM) application. Specifically, the application of exogenous ABA (50 μM) increased Pn, chlorophyll content and Fv/Fm by 28.39 %, 30.45 % and 17.29 %, respectively, compared with alkali stress alone. Furthermore, exogenous ABA treatment reduced alkali stress-induced superoxide anions (O2∙−) and hydrogen peroxide (H2O2), malondialdehyde (MDA), and electrolyte leakage, as well as higher proline content and activities of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX). Additionally, exogenous ABA (50 μM) decreased O2∙−, H2O2, MDA, electrolyte leakage by 38.64 %, 28.16 %, 39.29 % and 39.42 %, respectively, respect to alkali stress alone. Moreover, exogenous ABA reduced the Na+, increased K+ and K+/Na+ ratio, as well as the phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS), chalcone isomerase (CHI) activities and flavonoid content, and increased zeaxanthin epoxidase (ZEP) and 9-cis-epoxy carotenoid dioxygenase (NCED) activities and endogenous ABA levels in alkali stress-treated grapevines. Exogenous ABA (50 μM) increased flavonoid content and endogenous ABA content by 74.03 % and 20.84 %, compared with alkali stress alone, respectively. Conversely, exogenous fluridone exacerbated alkali stress-induced physiological damage in grapevine plants. Transcriptome analysis revealed that exogenous ABA (50 μM) and fluridone significantly induced the ‘Plant hormone signal transduction (ko04075)’, the ‘MAPK signaling pathway-plant (ko04016)’, ‘ABC transporters (ko02010)’, ‘Photosynthesis-antenna proteins (ko00196)’, ‘Flavonoid biosynthesis (ko00941)’, ‘Phenylpropanoid biosynthesis (ko00940)’ and other biological pathways and key gene involved in chlorophyll metabolism and ion transport. In conclusion, ABA markedly enhanced grapevines tolerance to alkali stress by modulating key biological pathways and physiological characteristics.

RNA splicing modulates the postharvest physiological deterioration of cassava storage root.

Rapid postharvest physiological deterioration (PPD) of cassava (Manihot esculenta Crantz) storage roots is a major constraint that limits the potential of this plant as a food and industrial crop. Extensive studies have been performed to explore the regulatory mechanisms underlying the PPD processes in cassava to understand their molecular and physiological responses. However, the exceptional functional versatility of alternative splicing (AS) remains to be explored during the PPD process in cassava. Here, we identified several aberrantly spliced genes during the early PPD stage. An in-depth analysis of AS revealed that the abscisic acid (ABA) biosynthesis pathway might serve as an additional molecular layer in attenuating the onset of PPD. Exogenous ABA application alleviated PPD symptoms through maintaining ROS generation and scavenging. Interestingly, the intron retention transcript of MeABA1 (ABA DEFICIENT 1) was highly correlated with PPD symptoms in cassava storage roots. RNA yeast 3-hybrid and RNA immunoprecipitation (RIP) assays showed that the serine/arginine-rich protein MeSCL33 (SC35-like splicing factor 33) binds to the precursor mRNA of MeABA1. Importantly, overexpressing MeSCL33 in cassava conferred improved PPD resistance by manipulating the AS and expression levels of MeABA1 and then modulating the endogenous ABA levels in cassava storage roots. Our results uncovered the pivotal role of the ABA biosynthesis pathway and RNA splicing in regulating cassava PPD resistance and proposed the essential roles of MeSCL33 for conferring PPD resistance, broadening our understanding of SR proteins in cassava development and stress responses.

Integrated proteomic, transcriptomic, and metabolomic profiling reveals that the gibberellin-abscisic acid hub runs flower development in the Chinese orchid Cymbidium sinense.

The seasonal flowering Chinese Cymbidium produce an axillary floral meristem and require a dormancy period during cold conditions for flower development. However, the bud activation mechanism remains elusive. This study evaluates the multi-omics across six stages of flower development, along with functional analysis of core genes to decipher the innate mechanism of floral bud initiation and outgrowth in the Chinese orchid Cymbidium sinense. Transcriptome and proteome analyses identified 10 modules with essential roles in floral bud dormancy and activation. Gene clusters in the early stages of flower development were mainly related to flowering time regulation and meristem determination, while the late stages were correlated with hormone signaling pathways. The metabolome identified 69 potential hormones in which gibberellin (GA) and abscisic acid (ABA) were the main regulatory hubs, and GA4 and GA53 exhibited a reciprocal loop. Extraneous GA application caused rapid elongation of flower buds and promoted the expression of flower development genes. Contrarily, exogenous ABA application extended the dormancy process and ABA inhibitors induced dormancy release. Moreover, CsAPETALA1 (CsAP1) was identified as the potential target of ABA for floral bud activation. Transformation of CsAP1 in Arabidopsis and its transient overexpression in C. sinense protoplasts not only affected flowering time and floral organ morphogenesis in Arabidopsis but also orchestrated the expression of flowering and hormone regulatory genes. The presence of ABA response elements in the CsAP1 promoter, rapid downregulation of CsAP1 after exogenous ABA application, and the activation of the floral bud after ABA inhibitor treatment suggest that ABA can control bud outgrowth through CsAP1.

Exogenous abscisic acid induces the formation of a suberized barrier to radial oxygen loss in adventitious roots of barley (Hordeum vulgare).

Internal root aeration is essential for root growth in waterlogged conditions. Aerenchyma provides a path for oxygen to diffuse to the roots. In most wetland species, including rice, a barrier to radial oxygen loss (ROL) allows more of the oxygen to diffuse to the root tip, enabling root growth into anoxic soil. Most dryland crops, including barley, do not form a root ROL barrier. We previously found that abscisic acid (ABA) signalling is involved in the induction of ROL barrier formation in rice during waterlogging. Although rice typically does not form a tight ROL barrier in roots in aerated conditions, an ROL barrier with suberized exodermis was induced by application of exogenous ABA. Therefore, we hypothesized that ABA application could also trigger root ROL barrier formation with hypodermal suberization in barley. Formation of an ROL barrier was examined in roots in different exogenous ABA concentrations and at different time points using cylindrical electrodes and Methylene Blue staining. Additionally, we evaluated root porosity and observed suberin and lignin modification. Suberin, lignin and Casparian strips in the cell walls were observed by histochemical staining. We also evaluated the permeability of the apoplast to a tracer. Application of ABA induced suberization and ROL barrier formation in the adventitious roots of barley. The hypodermis also formed lignin-containing Casparian strips and a barrier to the infiltration of an apoplastic tracer (periodic acid). However, ABA application did not affect root porosity. Our results show that in artificial conditions, barley can induce the formation of ROL and apoplastic barriers in the outer part of roots if ABA is applied exogenously. The difference in ROL barrier inducibility between barley (an upland species) and rice (a wetland species) might be attributable to differences in ABA signalling in roots in response to waterlogging conditions.

ZmADF5, a Maize Actin-Depolymerizing Factor Conferring Enhanced Drought Tolerance in Maize.

Drought stress is seriously affecting the growth and production of crops, especially when agricultural irrigation still remains quantitatively restricted in some arid and semi-arid areas. The identification of drought-tolerant genes is important for improving the adaptability of maize under stress. Here, we found that a new member of the actin-depolymerizing factor (ADF) family; the ZmADF5 gene was tightly linked with a consensus drought-tolerant quantitative trait locus, and the significantly associated signals were detected through genome wide association analysis. ZmADF5 expression could be induced by osmotic stress and the application of exogenous abscisic acid. Its overexpression in Arabidopsis and maize helped plants to keep a higher survival rate after water-deficit stress, which reduced the stomatal aperture and the water-loss rate, as well as improved clearance of reactive oxygen species. Moreover, seventeen differentially expressed genes were identified as regulated by both drought stress and ZmADF5, four of which were involved in the ABA-dependent drought stress response. ZmADF5-overexpressing plants were also identified as sensitive to ABA during the seed germination and seedling stages. These results suggested that ZmADF5 played an important role in the response to drought stress.

Timing of systemic resistance induced by local exogenous ABA application within clonal network of stoloniferous herb Centella asiatica subjected to low water availability.

Resistance traits of plants can be activated both at the damaged site and undamaged parts. Systemic resistance induced by local exogenous abscisic acid (ABA) application alleviated negative effect of low water availability on growth performance of clonal plant. However, timing of systemic resistance was poorly understood. Timing of systemic resistance refers to its activation and decay time within clonal network. Clonal fragment of Centella asiatica with four successive ramets (including first-oldest, second-older, third-old and fourth-young ramets) subjected to low water availability (20% soil moisture content) was used to explore effects of local exogenous ABA application on the timing of resistance activation and decay. Systemic resistance activated by local exogenous ABA application after 4 days remained at least 28 days. Compared with control, biomass accumulation of whole clonal fragment, root biomass and ratio of belowground to aboveground biomass significantly increased by local exogenous ABA application after 28 days. It is suggested that rapid activation and delay of resistance response induced by local exogenous ABA application within clonal network may improve fitness of clonal plant subjected to abiotic stress.

Cuticular wax biosynthesis in blueberries (Vaccinium corymbosum L.): Transcript and metabolite changes during ripening and storage affect key fruit quality traits.

In fruits, cuticular waxes affect fruit quality traits such as surface color at harvest and water loss during postharvest storage. This study investigated the transcriptional regulation of cuticular wax deposition in northern highbush blueberries (Vaccinium corymbosum L.) in relation to fruit water loss and surface color during ripening and postharvest storage, as well as the effects of abscisic acid (ABA)-mediated changes in cuticular wax deposition on these fruit quality traits. Total cuticular wax content (μg∙cm-2) decreased during fruit ripening and increased during postharvest storage. Transcriptome analysis revealed a transcript network for cuticular wax deposition in blueberries. Particularly, five OSC-Likes were identified as putative genes for triterpene alcohol production, with OSC-Like1 and OSC-Like2 encoding mixed amyrin synthases, OSC-Like3 encoding a lupeol synthase, and OSC-Like4 and OSC-Like5 encoding cycloartenol synthases. The expression of three CYP716A-like genes correlated to the accumulation of two triterpene acids oleanolic acid and ursolic acid, the major wax compounds in blueberries. Exogenous ABA application induced the expression of triterpenoid biosynthetic genes and the accumulation of β-amyrin and oleanolic acid, as well as increased the ratio of oleanolic acid to ursolic acid. These changes were associated with reduced fruit water loss. The content of β-diketones was also increased by ABA application, and this increase was associated with increased fruit lightness (measured as L* using CIELAB Color Space by a colorimeter). This study provided key insights on the molecular basis of cuticular wax deposition and its implications on fruit quality traits in blueberries.

Transcriptomic and physiological analyses reveal that jasmonic acid and abscisic acid coordinately regulate cold stress response in Myriophyllum aquaticum

Myriophyllum aquaticum, renowned for its ability to purify aquaculture wastewater, faces a significant challenge due to its susceptibility to cold stress. However, the molecular mechanisms underlying M. aquaticum's response to cold stress remain poorly understood. In this study, we unraveled the molecular mechanisms governing M. aquaticum's response to cold stress through transcriptome sequencing and physiological analyses. Our investigation revealed 12,684 differentially expressed genes during cold stress. Gene ontology and KEGG analyses demonstrated the involvement of plant hormone signaling and transcriptional reprogramming related genes in M. aquaticum's response to cold stress. Further investigations highlighted the role of jasmonic acid (JA) and abscisic acid (ABA) in M. aquaticum's cold acclimation. Firstly, cold stress significantly increased endogenous levels of JA and ABA in M. aquaticum plants. Secondly, the transcript levels of several crucial JA and ABA signaling genes were prominently elevated, as shown by expression profiling and qRT-PCR analyses. Thirdly, the application of exogenous JA or ABA effectively mitigated foliar damage and improved cold tolerance in M. aquaticum plants. Furthermore, the expression of JA and ABA biosynthesis and signaling genes was significantly upregulated in JA- or ABA-pretreated plants when exposed to cold stress. Collectively, our findings provide evidence that JA and ABA contribute to the cold acclimation of M. aquaticum plants. Our research provides insights into the molecular mechanisms underlying cold acclimation of M. Aquaticum plants and presents a novel strategy to improve their cold tolerance, thereby expanding their potential application in phytoremediation efforts in high latitude areas.

Hormone and transcriptomic analysis revealed that ABA and BR are key factors in the formation of inter‐subgeneric hybridization barrier in water lily

AbstractUnderstanding the process of signal communication between pollen and stigma is of significant importance for plant sexual reproduction. In the case of inter‐subgeneric hybridization in water lily, a pre‐fertilization hybridization barrier exists, the regulatory mechanism of which remains unclear. In this study, we conducted hormone and transcriptome analyses of unpollinated stigmas (Mock), self‐pollinated stigmas (SP), cross‐pollinated stigmas within the same subgenus (CP), and inter‐subgenus cross‐pollination stigmas (ISCP) in water lily to elucidate the formation mechanism of the inter‐subgeneric hybridization barrier. Our results indicated that the lack of abscisic acid (ABA) and brassinolide (BR) in ISCP stigmas are key factors contributing to the formation of the inter‐subgeneric hybridization barrier in water lily. Exogenous application of ABA and BR can help overcome the barrier between inter‐subgeneric water lily crosses. Through transcriptome analysis, we identified nine candidate genes involved in regulating the inter‐subgeneric hybridization barrier in water lily. In addition, we further demonstrated the importance of the NCED2‐mediated ABA synthesis pathway in the pollination process through AS‐ODN technology. Our study confirms that ABA and BR are critical for breaking the inter‐subgeneric hybridization barrier. The identification of the nine candidate genes provides important clues for further research on the hybridization recognition mechanism in water lily.

ABA-CsABI5-CsCalS11 module upregulates Callose deposition of citrus infected with Candidatus Liberibacter asiaticus.

Huanglongbing (HLB) primarily caused by Candidatus Liberibacter asiaticus (CLas) has been threatening citrus production globally. Under HLB conditions, an excessive accumulation of the polysaccharide callose in citrus phloem occurs, leading to phloem blockage and starch accumulation in leaves. The callose production is controlled by callose synthases (CalS), which have multiple members within plants. However, the knowledge of callose production in the citrus upon infection with CLas is limited. In this study, we firstly identified 11 CalSs in the Citrus sinensis genome through bioinformatics and found the expression pattern of CsCalS11 exhibited a positive correlation with callose deposition in CLas-infected leaves (correlation coefficient of 0.77, P ≤ 0.05). Knockdown of CsCalS11 resulted in a reduction of callose deposition and starch accumulation in CLas-infected citrus. Interestingly, we observed significantly higher concentrations of abscisic acid (ABA) in HLB-infected citrus leaves compared to uninfected ones. Furthermore, the expressions of CsABI5, CsPYR, and CsSnRK2 in the ABA pathway substantially increased in citrus leaves upon CLas infection. Additionally, the expression of CsCalS11 was significantly upregulated in citrus leaves following the application of exogenous ABA. We confirmed that CsABI5, a pivotal component of the ABA signaling pathway, regulates CsCalS11 expression by binding to its promoter using yeast one-hybrid assay, dual luciferase assay, and transient expression in citrus leaves. In conclusion, our findings strongly suggest that the CsABI5-CsCalS11 module plays a crucial role in regulating callose deposition through the ABA signaling pathway during CLas infection. The results also revealed new function of the ABA signaling pathway in plants under biotic stress.

Exogenous abscisic acid treatment regulates protein secretion in sorghum cell suspension cultures

ABSTRACT Drought stress adversely affects plant growth, often leading to total crop failure. Upon sensing soil water deficits, plants switch on biosynthesis of abscisic acid (ABA), a stress hormone for drought adaptation. Here, we used exogenous ABA application to dark-grown sorghum cell suspension cultures as an experimental system to understand how a drought-tolerant crop responds to ABA. We evaluated intracellular and secreted proteins using isobaric tags for relative and absolute quantification. While the abundance of only ~ 7% (46 proteins) intracellular proteins changed in response to ABA, ~32% (82 proteins) of secreted proteins identified in this study were ABA responsive. This shows that the extracellular matrix is disproportionately targeted and suggests it plays a vital role in sorghum adaptation to drought. Extracellular proteins responsive to ABA were predominantly defense/detoxification and cell wall-modifying enzymes. We confirmed that sorghum plants exposed to drought stress activate genes encoding the same proteins identified in the in vitro cell culture system with ABA. Our results suggest that ABA activates defense and cell wall remodeling systems during stress response. This could underpin the success of sorghum adaptation to drought stress.