Barley ABI5 (Abscisic Acid INSENSITIVE 5) Is Involved in Abscisic Acid-Dependent Drought Response

Abstract

ABA INSENSITIVE 5 (ABI5) is a basic leucine zipper (bZIP) transcription factor which acts in the abscisic acid (ABA) network and is activated in response to abiotic stresses. However, the precise role of barley (Hordeum vulgare) ABI5 in ABA signaling and its function under stress remains elusive. Here, we show that HvABI5 is involved in ABAdependent regulation of barley response to drought stress. We identified barley TILLING mutants carrying different alleles in the HvABI5 gene and we studied in detail the physiological and molecular response to drought and ABA for one of them. The hvabi5.d mutant, carrying G1751A transition, was insensitive to ABA during seed germination, yet it showed the ability to store more water than its parent cv. "Sebastian" (WT) in response to drought stress. The drought-tolerant phenotype of hvabi5.d was associated with better membrane protection, higher flavonoid content, and faster stomatal closure in the mutant under stress compared to the WT. The microarray transcriptome analysis revealed up-regulation of genes associated with cell protection mechanisms in the mutant. Furthermore, HvABI5 target genes: HVA1 and HVA22 showed higher activity after drought, which may imply better adaptation of hvabi5.d to stress. On the other hand, chlorophyll content in hvabi5.d was lower than in WT, which was associated with decreased photosynthesis efficiency observed in the mutant after drought treatment. To verify that HvABI5 acts in the ABA-dependent manner we analyzed expression of selected genes related to ABA pathway in hvabi5.d and its WT parent after drought and ABA treatments. The expression of key genes involved in ABA metabolism and signaling differed in the mutant and the WT under stress. Droughtinduced increase of expression of HvNCED1, HvBG8, HvSnRK2.1, and HvPP2C4 genes was 2-20 times higher in hvabi5.d compared to "Sebastian". We also observed a faster stomatal closure in hvabi5.d and much higher induction of HvNCED1 and HvSnRK2.1 genes after ABA treatment. Together, these findings demonstrate that HvABI5 plays a role in regulation of drought response in barley and suggest that HvABI5 might be engaged in the fine tuning of ABA signaling by a feedback regulation between biosynthetic and signaling events. In addition, they point to different mechanisms of HvABI5 action in regulating drought response and seed germination in barley.

Maize ZmbZIP33 Is Involved in Drought Resistance and Recovery Ability Through an Abscisic Acid-Dependent Signaling Pathway

“…Following this, hydrogen peroxide reduction is catalyzed by a peroxidase which removes active oxygen. Collin et al confirmed that increased expression of POD and SOD reduces drought-induced damages in barley (Collin et al, 2020 ). This study found that under drought stress and rewatering, lower SOD and POD activities were measured in the BMV-ZmbZIP33 mutant than BMV ( Figures 6C,D ).…”

“…In Barley, overexpression of HvABI5 increases HvSnRK2.1 expression, enabling the amplification of ABA signaling and activation of ABA-related genes. Under drought stress, HvABI5 directly upregulated of ABA synthesis, and ABA signaling via induction of HvPP2C4 and HvSnRK2.1 in response to drought stress (Collin et al, 2020 ).…”

Genome-Wide Identification and Expression Analysis of OsbZIP09 Target Genes in Rice Reveal Its Mechanism of Controlling Seed Germination

“…The ABA signaling pathway mainly relies on OsbZIP transcription factors, including AREBs, ABFs, and ABI5. Among these, ABI5 plays a key role in suppressing ABA-mediated seed germination and post-germination growth in a number of plant species, such as Arabidopsis [13,40,41], rice [42], wheat [43,44], barley [45], and Sorghum [46]. In addition to the roles of these classical bZIP transcriptional factors in the ABA pathway, several other bZIP members are also involved in the ABAmediated regulation of seed dormancy and germination in rice.…”

Plant-Specific AtS40.4 Acts as a Negative Regulator in Abscisic Acid Signaling During Seed Germination and Seedling Growth in Arabidopsis

“…ABREs are major cis-acting regulators in ABA-dependent gene expression ( Kim et al, 2004 ; Wang et al, 2019 ; Chen et al, 2020 ). ABI3, ABI4, and ABI5 bind directly to the ABREs of the promoter regions of a subset of genes, thereby controlling their transcription levels ( Carles et al, 2002 ; Ezcurra et al, 2000 ; Mizoi et al, 2012 ; Shu et al, 2013 ; Skubacz et al, 2016 ; Wang et al, 2019 ; Chandrasekaran et al, 2020 ; Collin et al, 2020 ). Notably, ABI3, ABI4, and ABI5 either activate or repress gene expression in diverse processes depending on DNA binding.…”