ABRE‐BINDING FACTORS play a role in the feedback regulation of ABA signaling by mediating rapid ABA induction of ABA co‐receptor genes

Abstract

Group A protein phosphatase 2Cs (PP2Cs) are abscisic acid (ABA) co-receptors that negatively regulate the ABA signaling pathway by inhibiting the downstream SnRK2 protein kinases. It has long been observed that exogenous ABA treatments dramatically induce the expression of group A PP2C genes, but the underlying molecular mechanisms and the biological significance remain largely unknown. Here, by using GUS reporter transgenic lines in which various lengths of ABI1 and ABI2 promoters were used to drive GUS gene expression, we defined the promoter fragments that confer ABA inducibility to ABI1 and ABI2. We further showed that ABRE-binding factors (ABFs), the bZIP family transcription factors, directly bind to the promoters of group A PP2C genes, and mediate rapid induction of their expression on exogenous ABA treatments. Moreover, our data indicated that ABA dramatically induces the expression of ABF genes and the accumulation of endogenous ABF proteins, and that ABFs themselves are involved in this induction, thus providing another layer of ABA regulation towards ABF proteins in addition to the well-characterized ABA-induced phosphorylation by SnRK2 protein kinases. Together, our data demonstrate that ABFs mediate rapid ABA induction of group A PP2C genes, thus playing a role in the negative feedback regulation of ABA signaling.

Abscisic acid dynamics, signaling, and functions in plants

“…Plant growth and stress responses are carefully controlled by both activity and abundance of PP2Cs. Although ABA and abiotic stresses inactivate PP2Cs to induce stress responses, the expression levels of PP2Cs are actually upregulated by abiotic stresses and ABA through ABRE‐BINDING FACTORS (ABFs), creating a feedback control loop to maintain new homeostatic levels (Bhaskara et al 2012, 2017; Wang et al 2019). Also, under unstressed conditions or transition from stressed to unstressed conditions, ABA and abiotic stress signaling needs to be suppressed to appropriately promote plant growth.…”

“…Exogenous ABA can also promote the elongation of the seedling primary root in the pyl112458 and pyl duodecuple mutants (Gonzalez‐Guzman et al 2012; Zhao et al 2018). Genes in the clade A PP2C family are intensively induced by ABA in the root and this may lead to decreased inhibition of primary root growth (Wang et al 2019). In addition to root growth, ABA inhibits the emergence of vegetative leaves under non‐stress conditions (Yoshida et al 2019).…”

Root Growth Adaptation is Mediated by PYLs ABA Receptor‐PP2A Protein Phosphatase Complex

“…[22,23] In agreement with these reports, ABA treatments led to a pronounced decrease in the density of both initiated primordia and emerged lateral roots in wild-type Arabidopsis thaliana plants (Figure S1a, Supporting Information). [26] The well-established ABA-insensitive dominant mutant abi1-1 (in the Col-0 background) [27,28] is less sensitive to ABA in terms of lateral root elongation. A higher-order mutant lacking five ABA receptors (PYR1, PYL1, PYL4, PYL5, and PYL8; abbreviated as 11458 mutant) was also completely resistant to ABA ( Figure S1b,c, Supporting Information), [24,25] and showed increased lateral root density and impaired gravitropic root growth even under normal growth conditions ( Figure S1b,c, Supporting Information).…”

Chloroplastic Os3BGlu6 contributes significantly to cellular ABA pools and impacts drought tolerance and photosynthesis in rice

“…ABA also plays a crucial role in plant responses to several abiotic stresses such as drought, salt and cold (North et al , ). In seeds, ABA is involved in embryo development, desiccation tolerance, dormancy and germination (Wang et al , ). Additionally, ABA is involved in regulating the stomatal opening, a process crucial for controlling CO 2 concentrations for photosynthesis and water release for transpiration (Kim et al , ; He et al , ).…”