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The nuclear pore complex (NPC) has multiple functions beyond the nucleo-cytoplasmic transport of large molecules. Subnuclear compartmentalization of chromatin is critical for gene expression in animals and yeast. However, the mechanism by which the NPC regulates gene expression is poorly understood in plants. Here we report that the Y-complex (Nup107-160 complex, a subcomplex of the NPC) self-maintains its nucleoporin homeostasis and modulates FLOWERING LOCUS C (FLC) transcription via changing histone modifications at this locus. We show that Y-complex nucleoporins are intimately associated with FLC chromatin through their interactions with histone H2A at the nuclear membrane. Fluorescence in situ hybridization assays revealed that Nup96, a Y-complex nucleoporin, enhances FLC positioning at the nuclear periphery. Nup96 interacted with HISTONE DEACETYLASE 6 (HDA6), a key repressor of FLC expression via histone modification, at the nuclear membrane to attenuate HDA6-catalyzed deposition at the FLC locus and change histone modifications. Moreover, we demonstrate that Y-complex nucleoporins interact with RNA polymerase II to increase its occupancy at the FLC locus, facilitating transcription. Collectively, our findings identify an attractive mechanism for the Y-complex in regulating FLC expression via tethering the locus at the nuclear periphery and altering its histone modification., Competing Interests: Conflict of interest statement. The authors declare no competing interests., (© The Author(s) 2023. Published by Oxford University Press on behalf of American Society of Plant Biologists. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Recent investigations in Arabidopsis thaliana suggest that SUPPRESSOR of MORE AXILLARY GROWTH 2 1 (SMAX1) and SMAX1-LIKE2 (SMXL2) are negative regulators of karrikin (KAR) and strigolactone (SL) signaling during plant growth and development, but their functions in drought resistance and related mechanisms of action remain unclear. To understand the roles and mechanisms of SMAX1 and SMXL2 in drought resistance, we investigated the drought-resistance phenotypes and transcriptome profiles of smax1 smxl2 (s1,2) double-mutant plants in response to drought stress. The s1,2 mutant plants showed enhanced drought-resistance and lower leaf water loss when compared with wild-type (WT) plants. Transcriptome comparison of rosette leaves from the s1,2 mutant and the WT under normal and dehydration conditions suggested that the mechanism related to cuticle formation was involved in drought resistance. This possibility was supported by enhanced cuticle formation in the rosette leaves of the s1,2 mutant. We also found that the s1,2 mutant plants were more sensitive to abscisic acid in assays of stomatal closure, cotyledon opening, chlorophyll degradation and growth inhibition, and they showed a higher reactive oxygen species detoxification capacity than WT plants. In addition, the s1,2 mutant plants had longer root hairs and a higher root-to-shoot ratio than the WT plants, suggesting that the mutant had a greater capacity for water absorption than the WT. Taken together, our results indicate that SMAX1 and SMXL2 negatively regulate drought resistance, and disruption of these KAR- and SL-signaling-related genes may therefore provide a novel means for improving crop drought resistance., (© The Author(s) 2022. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Sinapate esters, which are induced in plants under ultraviolet-B (UV-B) irradiation, have important roles not only in the protection against UV-B irradiation but also in the regulation of stomatal closure. Here, we speculated that sinapate esters would function in the stomatal closure of Arabidopsis thaliana in response to UV-B. We measured the stomatal aperture size of the wild-type (WT) and bright trichomes 1 (brt1) and sinapoylglucose accumulator 1 (sng1) mutants under UV-B irradiation; the latter two mutants are deficient in the conversion of sinapic acid to sinapoylglucose (SG) and SG to sinapoylmalate (SM), respectively. Both the brt1 and sng1 plants showed smaller stomatal apertures than the WT under normal light and UV-B irradiation conditions. The accumulation of SM and malate were induced by UV-B irradiation in WT and brt1 plants but not in sng1 plants. Consistently, exogenous malate application reduced UV-B-induced stomatal closure in WT, brt1 and sng1 plants. Nonetheless, levels of reactive oxygen species (ROS), nitric oxide (NO) and cytosolic Ca2+ were higher in guard cells of the sng1 mutant than in those of the WT under normal white light and UV-B irradiation, suggesting that disturbance of sinapate metabolism induced the accumulation of these signaling molecules that promote stomatal closure. Unexpectedly, exogenous sinapic acid application prevented stomatal closure of WT, brt1 and sng1 plants. In summary, we hypothesize that SG or other sinapate esters may promote the UV-B-induced malate accumulation and stomatal closure, whereas sinapic acid inhibits the ROS-NO pathway that regulates UV-B-induced cytosolic Ca2+ accumulation and stomatal closure., (© The Author(s) 2022. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

The karrikin (KAR) receptor and several related signaling components have been identified by forward genetic screening, but only a few studies have reported on upstream and downstream KAR signaling components and their roles in drought tolerance. Here, we characterized the functions of KAR UPREGULATED F-BOX 1 (KUF1) in drought tolerance using a reverse genetics approach in Arabidopsis (Arabidopsis thaliana). We observed that kuf1 mutant plants were more tolerant to drought stress than wild-type (WT) plants. To clarify the mechanisms by which KUF1 negatively regulates drought tolerance, we performed physiological, transcriptome, and morphological analyses. We found that kuf1 plants limited leaf water loss by reducing stomatal aperture and cuticular permeability. In addition, kuf1 plants showed increased sensitivity of stomatal closure, seed germination, primary root growth, and leaf senescence to abscisic acid (ABA). Genome-wide transcriptome comparisons of kuf1 and WT rosette leaves before and after dehydration showed that the differences in various drought tolerance-related traits were accompanied by differences in the expression of genes associated with stomatal closure (e.g. OPEN STOMATA 1), lipid and fatty acid metabolism (e.g. WAX ESTER SYNTHASE), and ABA responsiveness (e.g. ABA-RESPONSIVE ELEMENT 3). The kuf1 mutant plants had higher root/shoot ratios and root hair densities than WT plants, suggesting that they could absorb more water than WT plants. Together, these results demonstrate that KUF1 negatively regulates drought tolerance by modulating various physiological traits, morphological adjustments, and ABA responses and that the genetic manipulation of KUF1 in crops is a potential means of enhancing their drought tolerance., (© American Society of Plant Biologists 2022. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Strigolactone and karrikin receptors, DWARF14 (D14) and KARRIKIN INSENSITIVE 2 (KAI2), respectively, have been shown to positively regulate drought resistance in Arabidopsis thaliana by modulating abscisic acid responsiveness, anthocyanin accumulation, stomatal closure, cell membrane integrity and cuticle formation. Here, we aim to identify genes specifically or commonly regulated by D14 and KAI2 under water scarcity, using comparative analysis of the transcriptome data of the A. thaliana d14-1 and kai2-2 mutants under dehydration conditions. In comparison with wild-type, under dehydration conditions, the expression levels of genes related to photosynthesis and the metabolism of glucosinolates and trehalose were significantly changed in both d14-1 and kai2-2 mutant plants, whereas the transcript levels of genes related to the metabolism of cytokinins and brassinosteroids were significantly altered in the d14-1 mutant plants only. These results suggest that cytokinin and brassinosteroid metabolism might be specifically regulated by the D14 pathway, whereas photosynthesis and metabolism of glucosinolates and trehalose are potentially regulated by both D14 and KAI2 pathways in plant response to water scarcity.

The regulation of stomatal lineage cell development has been extensively investigated. However, a comprehensive characterization of this biological process based on single-cell transcriptome analysis has not yet been reported. In this study, we performed RNA sequencing on 12 844 individual cells from the cotyledons of 5-day-old Arabidopsis seedlings. We identified 11 cell clusters corresponding mostly to cells at specific stomatal developmental stages using a series of marker genes. Comparative analysis of genes with the highest variable expression among these cell clusters revealed transcriptional networks that regulate development from meristemoid mother cells to guard mother cells. Examination of the developmental dynamics of marker genes via pseudo-time analysis revealed potential interactions between these genes. Collectively, our study opens the door for understanding how the identified novel marker genes participate in the regulation of stomatal lineage cell development., (Copyright © 2020 The Author. Published by Elsevier Inc. All rights reserved.)

The reactive oxygen species (ROS) are continuously produced and are essential for mediating the growth and development of plants. However too much accumulation of ROS can result in the oxidative damage to cells, especially under the adverse environmental conditions. Plants have evolved sophisticated strategies to regulate the homeostasis of H 2 O 2 . In this study, we generated transgenic Arabidopsis plants in the Ws ecotype (Ws) background in which WRKY33 is co-suppressed (csWRKY33/Ws). Compared with Ws, csWRKY33/Ws plants accumulate more H 2 O 2 . RNA-seq analysis indicated that in csWRKY33/Ws plants, expression of oxidative stress related genes such as ascorbate peroxidase 2 (APX2) is affected. Over-expression of APX2 can rescue the phenotype of csWRKY33/Ws, suggesting that the changes in the growth of csWRKY33/Ws is duo to the higher accumulation of H 2 O 2 . Analysis of the CHIP-seq data suggested that WRKY33 can directly regulate the expression of PIF4, vice versa. qPCR analysis also confirmed that the mutual regulation between WRKY33 and PIF4. Similar to that of csWRKY33/Ws, and the accumulation of H 2 O 2 in pif4 also increased. Taken together, our results reveal a WRKY33-PIF4 regulatory loop that appears to play an important role in regulating the growth and development of seedlings by mediating H 2 O 2 homeostasis., Competing Interests: Declaration of competing interest The authors declare that they have no conflict of interest., (Copyright © 2020. Published by Elsevier Inc.)

Background: Starch is synthesized during daylight for temporary storage in leaves and then degraded during the subsequent night to support plant growth and development. Impairment of starch degradation leads to stunted growth, even senescence and death. The nuclear pore complex is involved in many cellular processes, but its relationship with starch degradation has been unclear until now. We previously identified that two Nucleoporin98 genes (Nup98a and Nup98b) redundantly regulate flowering via the CONSTANS (CO)-independent pathway in Arabidopsis thaliana. The double mutant also shows severe senescence phenotypes., Results: We find that Nucleoporin 98 participates in the regulation of sugar metabolism in leaves and is also involved in senescence regulation in Arabidopsis. We show that Nup98a and Nup98b function redundantly at different stages of starch degradation. The nup98a-1 nup98b-1 double mutant accumulates more starch, showing a severe early senescence phenotype compared to wild type plants. The expression of marker genes related to starch degradation is impaired in the nup98a-1 nup98b-1 double mutant, and marker genes of carbon starvation and senescence express their products earlier and in higher abundance than in wild type plants, suggesting that abnormalities in energy metabolism are the main cause of senescence in the double mutant. Addition of sucrose to the growth medium rescues early senescence phenotypes of the nup98a-1 nup98b-1 mutant., Conclusions: Our results provide evidence for a novel role of the nuclear pore complex in energy metabolism related to growth and development, in which Nup98 functions in starch degradation to control growth regulation in Arabidopsis.

Previous investigations have shown that the SUPPRESSORS OF MAX2 1-LIKE6, 7 and 8 (SMXL6, 7 and 8) proteins redundantly repress strigolactone (SL) signaling in plant growth and development. Recently, a growing body of evidence indicated that SLs positively regulate plant drought resistance through functional analyses of genes involved in SL biosynthesis and positive regulation of SL signaling. However, the functions of the SL-signaling negative regulators SMXL6, 7 and 8 in drought resistance and the associated mechanisms remain elusive. To reveal the functions of these SMXL proteins, we analyzed the drought-resistant phenotype of the triple smxl6 , 7 , 8 mutant plants and studied several drought resistance-related traits. Our results showed that the smxl6 , 7 , 8 mutant plants were more resistant to drought than wild-type plants. Physiological investigations indicated that the smxl6 , 7 , 8 mutant plants exhibited higher leaf surface temperature, reduced cuticle permeability, as well as decreases in drought-induced water loss and cell membrane damage in comparison with wild-type plants. Additionally, smxl6 , 7 , 8 mutant plants displayed an increase in anthocyanin biosynthesis during drought, enhanced detoxification capacity and increased sensitivity to abscisic acid in cotyledon opening and growth inhibition assays. A good correlation between the expression levels of some relevant genes and the examined physiological and biochemical traits was observed. Our findings together indicate that the SMXL6, 7 and 8 act as negative regulators of drought resistance, and that disruption of these SMXL genes in crops may provide a novel way to improve their drought resistance.

The nuclear pore complex profoundly affects the timing of flowering; however, the underlying mechanisms are poorly understood. Here, we report that Nucleoporin96 ( Nup96 ) acts as a negative regulator of long-day photoperiodic flowering in Arabidopsis ( Arabidopsis thaliana ). Through multiple approaches, we identified the E3 ubiquitin ligase HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENE1 (HOS1) and demonstrated its interaction in vivo with Nup96. Nup96 and HOS1 mainly localize and interact on the nuclear membrane. Loss of function of Nup96 leads to destruction of HOS1 proteins without a change in their mRNA abundance, which results in overaccumulation of the key activator of long-day photoperiodic flowering, CONSTANS (CO) proteins, as previously reported in hos1 mutants. Unexpectedly, mutation of HOS1 strikingly diminishes Nup96 protein level, suggesting that Nup96 and HOS1 are mutually stabilized and thus form a novel repressive module that regulates CO protein turnover. Therefore, the nup96 and hos1 single and nup96 hos1 double mutants have highly similar early-flowering phenotypes and overlapping transcriptome changes. Together, this study reveals a repression mechanism in which the Nup96-HOS1 repressive module gates the level of CO proteins and thereby prevents precocious flowering in long-day conditions., (© 2020 American Society of Plant Biologists. All rights reserved.)

In order to withstand high light (HL) stress, plants have evolved both short-term defense and repair mechanisms and long-term acclimation responses. At present, however, the underlying signaling events and molecular mechanisms are still poorly understood. Analysis of the mutants coe1, coe1 gun1 double mutant and oeGUN1coe1 revealed increased sensitivity to HL stress as compared to wild type (WT), with oeGUN1 coe1 plants displaying the highest sensitivity. Accumulation of FTSH2 protein and degradation of D1 protein during the HL stress were shown to depend on both COE1 and GUN1. Overexpression of COE1 enhanced the induction of FTSH2 and the tolerance to HL stress. These results indicate that the COE1-GUN1 signaling pathway plays an important role in regulating the adaptation of plants to HL., (Copyright © 2019. Published by Elsevier Inc.)

As a scaffold protein, Receptor for Activated C Kinase 1a (RACK1) interacts with many proteins and is involved in multiple biological processes in Arabidopsis. However, the global RACK1 protein interaction network in higher plants remains poorly understood. Here, we generated a yeast two-hybrid library using mixed samples from different developmental stages of Arabidopsis thaliana. Using RACK1a as bait, we performed a comprehensive screening of the resulting library to identify RACK1a interactors at the whole-transcriptome level. We selected 1065 independent positive clones that led to the identification of 215 RACK1a interactors. We classified these interactors into six groups according to their potential functions. Several interactors were selected for bimolecular fluorescence complementation (BiFC) analysis and their interaction with RACK1a was confirmed in vivo. Our results provide further insight into the molecular mechanisms through which RACK1a regulates various growth and development processes in higher plants., (Copyright © 2019. Published by Elsevier Inc.)

Key Message: Two redundant nucleoporin genes Nup98a and Nup98b bypass the CO-check point in photoperiodic signaling and integrated signals from multiple pathways to directly target FT for flowering control in Arabidopsis. Flowering regulation is an important and widely studied plant development event. Even though nucleoporin Nup98 has been proven to play pivotal roles in the growth and development of mammalian cells and yeast, it is still unknown if Nup98 participates in flowering control in plants. In this study, we investigated the function of two Nup98 homologs, Nup98a and Nup98b, in flowering regulation in Arabidopsis. The results showed that Nup98a and Nup98b redundantly inhibit flowering through multiple pathways including clock, photoperiod, and age pathways. Single mutants of nup98a and nup98b do not show any obvious abnormal phenotypes compared to wild-type plants; however, the nup98a1 nup98b1 double mutant displays early flowering. Significantly, Nup98a/Nup98b gate flowering in a CONSTANS (CO)-independent mode. Therefore, Nup98a/Nup98b bypasses the CO checkpoint in photoperiodic signaling and integrated signals from multiple pathways to directly target FLOWERING LOCUS T (FT) for flowering control. In addition, our results provide a line of genetic evidence for uncoupling the mechanism of flowering and senescence at Nup98a/Nup98b genes in Arabidopsis, which are classically recognized as two coupled developmental events.

Background: Sinapic acid and its esters have broad functions in different stages of seed germination and plant development and are thought to play a role in protecting against ultraviolet irradiation. To better understand the interactions between sinapic acid esters and seed germination processes in response to various stresses, we analyzed the role of the plant hormone abscisic acid (ABA) in the regulation of sinapic acid esters involved in seed germination and early seedling growth., Results: We found that exogenous sinapic acid promotes seed germination in a dose-dependent manner in Arabidopsis thaliana. High-performance liquid chromatography mass spectrometry analysis showed that exogenous sinapic acid increased the sinapoylcholine content of imbibed seeds. Furthermore, sinapic acid affected ABA catabolism, resulting in reduced ABA levels and increased levels of the ABA-glucose ester. Using mutants deficient in the synthesis of sinapate esters, we showed that the germination of mutant sinapoylglucose accumulator 2 (sng2) and bright trichomes 1 (brt1) seeds was more sensitive to ABA than the wild-type. Moreover, Arabidopsis mutants deficient in either abscisic acid deficient 2 (ABA2) or abscisic acid insensitive 3 (ABI3) displayed increased expression of the sinapoylglucose:choline sinapoyltransferase (SCT) and sinapoylcholine esterase (SCE) genes with sinapic acid treatment. This treatment also affected the accumulation of sinapoylcholine and free choline during seed germination., Conclusions: We demonstrated that sinapoylcholine, which constitutes the major phenolic component in seeds among various minor sinapate esters, affected ABA homeostasis during seed germination and early seedling growth in Arabidopsis. Our findings provide insights into the role of sinapic acid and its esters in regulating ABA-mediated inhibition of Arabidopsis seed germination in response to drought stress.

Abscisic acid (ABA) plays roles in plant growth and development and in stress responses. Recently, we found that ABA regulates ABA-insensitive protein kinase 1 (AIK1), a mitogen-activated protein kinase kinase kinase. Compared with wild-type, aik1-1 showed downregulation of ABA-responsive genes (RD29A, MYC2, ABI3 and ABI4). Under ABA treatment, the transcript level of KRP1 (Kip-related protein, a cyclin-dependent kinase inhibitor) was lower in aik1-1 than in wild-type. The activity of ABA-activated MPK6 was decreased in abi1 abi2, and abi1 abi2 hab1, and increased in snrk2.2 snrk2.3 and pyr1 pyl1 pyl2 pyl4 mutants. These results indicated that AIK1-MKK5-MPK6 functions in ABA responses and requires ABA-responsive gene expression to regulate ABA-inhibited root growth and cell division. The ABA signaling pathway regulates this MAPK cascade.

The mitogen-activated protein kinase (MAPK) cascade is an evolutionarily conserved signal transduction module involved in transducing extracellular signals to the nucleus for appropriate cellular adjustment. This cascade essentially consists of three components: a MAPK kinase kinase (MAPKKK), a MAPK kinase, and a MAPK, connected to each other by the event of phosphorylation. Here, we report the characterization of a MAPKKK, ABA-INSENSITIVE PROTEIN KINASE1 (AIK1), which regulates abscisic acid (ABA) responses in Arabidopsis (Arabidopsis thaliana). T-DNA insertion mutants of AIK1 showed insensitivity to ABA in terms of both root growth and stomatal response. AIK1 functions in ABA responses via regulation of root cell division and elongation, as well as stomatal responses. The activity of AIK1 is induced by ABA in Arabidopsis and tobacco (Nicotiana benthamiana), and the Arabidopsis protein phosphatase type 2C, ABI1, a negative regulator of ABA signaling, restricts AIK1 activity by dephosphorylation. Bimolecular fluorescence complementation analysis showed that MPK3, MPK6, and AIK1 interact with MKK5. The single mutant seedlings of mpk6 and mkk5 have similar phenotypes to aik1, but mkk4 does not. AIK1 was localized in the cytoplasm and shown to activate MKK5 by protein phosphorylation, which was an ABA-activated process. Constitutively active MKK5 in aik1 mutant seedlings complements the ABA-insensitive root growth phenotype of aik1 The activity of MPK6 was increased by ABA in wild-type seedlings, but its activation by ABA was impaired in aik1 and aik1 mkk5 mutants. These findings clearly suggest that the AIK1-MKK5-MPK6 cascade functions in the ABA regulation of primary root growth and stomatal response., (© 2017 American Society of Plant Biologists. All Rights Reserved.)

Reactive oxygen species (ROS) have been characterized as both important signaling molecules and universal stressors that mediate many developmental and physiological responses. So far, details of the transcriptional mechanism of ROS-responsive genes are largely unknown. In the study reported here, we identified seven potential ROS-responsive cis-acting elements (ROSEs) from the promoters of genes up-regulated by ROS in Arabidopsis (Arabidopsis thaliana). We also found that the APETALA2/ethylene-responsive element binding factor6 (ERF6) could bind specifically to the ROSE7/GCC box. Coexpression of ERF6 enhanced luciferase activity driven by ROSE7. The deficient mutants of ERF6 showed growth retardation and higher sensitivity to photodamage. ERF6 interacted physically with mitogen-activated protein kinase6 (MPK6) and also served as a substrate of MPK6. MPK6-mediated ERF6 phosphorylation at both serine-266 and serine-269 affected the dynamic alternation of the ERF6 protein, which resulted in changes in ROS-responsive gene transcription. These data might provide new insight into the mechanisms that regulate ROS-responsive gene transcription via a complex of MPK6, ERF6, and the ROSE7/GCC box under oxidative stress or a fluctuating light environment.

Although the practice of protein engineering is industrially fruitful in creating biocatalysts and therapeutic proteins, applications of analogous techniques in the field of plant metabolic engineering are still in their infancy. Lignins are aromatic natural polymers derived from the oxidative polymerization of primarily three different hydroxycinnamyl alcohols, the monolignols. Polymerization of lignin starts with the oxidation of monolignols, followed by endwise cross-coupling of (radicals of) a monolignol and the growing oligomer/polymer. The para-hydroxyl of each monolignol is crucial for radical generation and subsequent coupling. Here, we describe the structure-function analysis and catalytic improvement of an artificial monolignol 4-O-methyltransferase created by iterative saturation mutagenesis and its use in modulating lignin and phenylpropanoid biosynthesis. We show that expressing the created enzyme in planta, thus etherifying the para-hydroxyls of lignin monomeric precursors, denies the derived monolignols any participation in the subsequent coupling process, substantially reducing lignification and, ultimately, lignin content. Concomitantly, the transgenic plants accumulated de novo synthesized 4-O-methylated soluble phenolics and wall-bound esters. The lower lignin levels of transgenic plants resulted in higher saccharification yields. Our study, through a structure-based protein engineering approach, offers a novel strategy for modulating phenylpropanoid/lignin biosynthesis to improve cell wall digestibility and diversify the repertories of biologically active compounds.

We isolated two T-DNA insertion mutants of Arabidopsis thaliana GLUTATHIONE PEROXIDASE3 (ATGPX3) that exhibited a higher rate of water loss under drought stress, higher sensitivity to H(2)O(2) treatment during seed germination and seedling development, and enhanced production of H(2)O(2) in guard cells. By contrast, lines engineered to overexpress ATGPX3 were less sensitive to drought stress than the wild type and displayed less transpirational water loss, which resulted in higher leaf surface temperature. The atgpx3 mutation also disrupted abscisic acid (ABA) activation of calcium channels and the expression of ABA- and stress-responsive genes. ATGPX3 physically interacted with the 2C-type protein phosphatase ABA INSENSITIVE2 (ABI2) and, to a lesser extent, with ABI1. In addition, the redox states of both ATGPX3 and ABI2 were found to be regulated by H(2)O(2). The phosphatase activity of ABI2, measured in vitro, was reduced approximately fivefold by the addition of oxidized ATGPX3. The reduced form of ABI2 was converted to the oxidized form by the addition of oxidized ATGPX3 in vitro, which might mediate ABA and oxidative signaling. These results suggest that ATGPX3 might play dual and distinctive roles in H(2)O(2) homeostasis, acting as a general scavenger and specifically relaying the H(2)O(2) signal as an oxidative signal transducer in ABA and drought stress signaling.