The basic helix‐loop‐helix transcription factor gene, OsbHLH38, plays a key role in controlling rice salt tolerance

Abstract

The plant hormone abscisic acid (ABA) is crucial for plant seed germination and abiotic stress tolerance. However, the association between ABA sensitivity and plant abiotic stress tolerance remains largely unknown. In this study, 436 rice accessions were assessed for their sensitivity to ABA during seed germination. The considerable diversity in ABA sensitivity among rice germplasm accessions was primarily reflected by the differentiation between the Xian (indica) and Geng (japonica) subspecies and between the upland‐Geng and lowland‐Geng ecotypes. The upland‐Geng accessions were most sensitive to ABA. Genome‐wide association analyses identified four major quantitative trait loci containing 21 candidate genes associated with ABA sensitivity of which a basic helix‐loop‐helix transcription factor gene, OsbHLH38, was the most important for ABA sensitivity. Comprehensive functional analyses using knockout and overexpression transgenic lines revealed that OsbHLH38 expression was responsive to multiple abiotic stresses. Overexpression of OsbHLH38 increased seedling salt tolerance, while knockout of OsbHLH38 increased sensitivity to salt stress. A salt‐responsive transcription factor, OsDREB2A, interacted with OsbHLH38 and was directly regulated by OsbHLH38. Moreover, OsbHLH38 affected rice abiotic stress tolerance by mediating the expression of a large set of transporter genes of phytohormones, transcription factor genes, and many downstream genes with diverse functions, including photosynthesis, redox homeostasis, and abiotic stress responsiveness. These results demonstrated that OsbHLH38 is a key regulator in plant abiotic stress tolerance.

OsNAC5 orchestrates OsABI5 to fine‐tune cold tolerance in rice

“…For example, Arabidopsis CONSTITUTIVELY PHOTOMORPHOGENIC 1 SUPPRESSOR 6 (CSU6) represses hypocotyl growth via transcriptional and biochemical regulation of PHYTOCHROME‐INTERACTING FACTOR 4 (PIF4) and PIF5 (Lan et al, 2022). By contrast, one recent study showed that a bHLH TF, bHLH38, dually regulates OsDREB2A at the transcriptional level and via direct protein–protein interaction to promote stress tolerance (Du et al, 2023). Previous studies (Takasaki et al, 2010; Song et al, 2011; Li et al, 2021) and our current results (Figures 1–4) suggest that OsNAC5 and OsABI5 regulate cold tolerance by controlling the interaction between ROS and phytohormones (e.g., ABA).…”

Population Structure and Genetic Diversity of Shanlan Landrace Rice for GWAS of Cooking and Eating Quality Traits

“…OsbHLH38 ( LOC_Os08g33590 ) is an alkaline helix-loop-helix transcription factor gene that is most important for ABA sensitivity. In addition, OsbHLH38 influences abiotic stress tolerance in rice by mediating the expression of a large number of plant hormone transporter genes, transcription factor genes, and many downstream genes with different functions, including photosynthesis, redox homeostasis, and abiotic stress reactivity [ 50 ]. Further transgenic experiments are needed to reveal the association between these genes and Tp.…”

Designing salt stress‐resilient crops: Current progress and future challenges

“…An important feature of the salt stress response is that the osmotic signal causes abscisic acid (ABA) to accumulate by inducing the expression of ABA biosynthesis genes (e.g., NINE‐CIS‐EPOXYCAROTENOID DIOXYGENASEs ( NCEDs ), ABA DEFICIENT ( ABA ), and ALDEHYDE OXIDASE 3 ( AO3 )), which elicits many adaptive responses in plants (van Zelm et al, 2020; Du et al, 2023). The salt‐induced increase in ABA is perceived by PYR/PYL/RCAR (pyrabactin resistance 1/PYR1‐like/regulatory component of ABA receptors) family receptors, which inhibit clade A‐type 2C protein phosphatase (PP2C) activities, thus activating subclass III SNF1‐related protein kinase 2s (SnRK2s) (Ma et al, 2009; Park et al, 2009; Vlad et al, 2009).…”