The IbPYL8–IbbHLH66–IbbHLH118 complex mediates the abscisic acid‐dependent drought response in sweet potato

Abstract

Drought limits crop development and yields. bHLH (basic helix-loop-helix) transcription factors play critical roles in regulating the drought response in many plants, but their roles in this process in sweet potato are unknown.Here, we report that two bHLH proteins, IbbHLH118 and IbbHLH66, play opposite roles in the ABA-mediated drought response in sweet potato. ABA treatment repressed IbbHLH118 expression but induced IbbHLH66 expression in the drought-tolerant sweet potato line Xushu55-2. Overexpressing IbbHLH118 reduced drought tolerance, whereas overexpressing IbbHLH66 enhanced drought tolerance, in sweet potato.IbbHLH118 directly binds to the E-boxes in the promoters of ABA-insensitive 5 (IbABI5), ABA-responsive element binding factor 2 (IbABF2) and tonoplast intrinsic protein 1 (IbTIP1) to suppress their transcription. IbbHLH118 forms homodimers with itself or heterodimers with IbbHLH66. Both of the IbbHLHs interact with the ABA receptor IbPYL8. ABA accumulates under drought stress, promoting the formation of the IbPYL8-IbbHLH66-IbbHLH118 complex. This complex interferes with IbbHLH118's repression of ABA-responsive genes, thereby activating ABA responses and enhancing drought tolerance.These findings shed light on the role of the IbPYL8-IbbHLH66-IbbHLH118 complex in the ABA-dependent drought response of sweet potato and identify candidate genes for developing elite crop varieties with enhanced drought tolerance.

Functions of Basic Helix–Loop–Helix (bHLH) Proteins in the Regulation of Plant Responses to Cold, Drought, Salt, and Iron Deficiency: A Comprehensive Review

“…Under drought, accumulated ABA promotes the formation of the ternary complex and interferes IbbHLH118's repression of ABA-responsive genes, thereby enhancing drought tolerance. 92 SlbHLH96 physically interacts with an ETHYLENE-RESPONSIVE FACTOR (SlERF4). This binary complex interferes the expression of the ABA catabolic gene (SlCYP707A2) through binding to its promoter.…”

“…By contrast, IbbHLH66, a positive regulator of drought response, interacts with IbbHLH118 and ABA receptor PYRABACTIN RESISTANCE 1/PYR-LIKE (IbPYL8) to form the IbPYL8–IbbHLH66–IbbHLH118 complex. Under drought, accumulated ABA promotes the formation of the ternary complex and interferes IbbHLH118’s repression of ABA-responsive genes, thereby enhancing drought tolerance . SlbHLH96 physically interacts with an ETHYLENE-RESPONSIVE FACTOR (SlERF4).…”

Genome-Wide Characterization of the PIFs Family in Sweet Potato and Functional Identification of IbPIF3.1 under Drought and Fusarium Wilt Stresses

“…Due to its strong adaptability and resistance, it is widely planted in drought, waterlogged, and saline areas [ 40 ]. Several genes have been reported to be associated with abiotic stress in sweet potato, including IbMIPS1 , IbC3H18 , IbBBX24 , ItfWRKY70 , IbPYL8 , IbbHLH66 , IbbHLH118 , and IbMYB48 [ 41 , 42 , 43 , 44 , 45 , 46 ]. Sweet potato is susceptible to many pests and diseases, which may cause huge economic losses in crop production.…”

MdMYB44‐like positively regulates salt and drought tolerance via the MdPYL8‐MdPP2CA module in apple

“…Plant stress tolerance is mediated by numerous classical phytohormones, including salicylic acid (SA), abscisic acid (ABA), jasmonic acid (JA), and ethylene (ETH) (An et al., 2018; Fujita et al., 2006; Skubacz et al., 2016). ABA is the most well‐known signaling molecule in mediating plant responses to salt and drought stress (Skubacz et al., 2016; Xue et al., 2022). For example, salt and drought stress trigger endogenous ABA production (Barrero et al., 2005; Guóth et al., 2009; Xiong & Zhu, 2002), and plant salt and drought resistance can be improved by exogenous ABA treatment (Etehadnia et al., 2008; Khadri et al., 2006; Wei et al., 2015).…”