Negative feedback regulation of ABA biosynthesis in peanut (Arachis hypogaea): a transcription factor complex inhibits AhNCED1 expression during water stress

Abstract

Abscisic acid (ABA), a key plant stress-signaling hormone, is produced in response to drought and counteracts the effects of this stress. The accumulation of ABA is controlled by the enzyme 9-cis-epoxycarotenoid dioxygenase (NCED). In Arabidopsis, NCED3 is regulated by a positive feedback mechanism by ABA. In this study in peanut (Arachis hypogaea), we demonstrate that ABA biosynthesis is also controlled by negative feedback regulation, mediated by the inhibitory effect on AhNCED1 transcription of a protein complex between transcription factors AhNAC2 and AhAREB1. AhNCED1 was significantly down-regulated after PEG treatment for 10 h, at which time ABA content reached a peak. A ChIP-qPCR assay confirmed AhAREB1 and AhNAC2 binding to the AhNCED1 promoter in response to ABA. Moreover, the interaction between AhAREB1 and AhNAC2, and a transient expression assay showed that the protein complex could negatively regulate the expression of AhNCED1. The results also demonstrated that AhAREB1 was the key factor in AhNCED1 feedback regulation, while AhNAC2 played a subsidiary role. ABA reduced the rate of AhAREB1 degradation and enhanced both the synthesis and degradation rate of the AhNAC2 protein. In summary, the AhAREB1/AhNAC2 protein complex functions as a negative feedback regulator of drought-induced ABA biosynthesis in peanut.

N-terminal domains of AhAREB1 protein are necessary for transcriptional characteristics and negative regulation of the AhNCED1 gene

“…Combined with above results, we assume that AhAREB1 may negatively regulate the expression of AhNCED1 by binding to the ABRE element in the AhNCED1 promoter. It is also consistent with what has been reported by Liu et al (2016a). , e, i, m, q -seedlings (bar = 4 mm); b, f, j, n, r -leaves (bar = 2 mm); c, g, k, o, s -siliquae (bar = 0.5 mm); d, h, l, p, t -flowers (bar = 2 mm).…”

“…Transgenic AhAREB1, A4, A5 and A6 peanut hairy roots were used for the ChIP assay and a p35S:GFP peanut hairy root was used as a negative control. The ChIP assay was performed as described by Liu et al (2016a) with minor modifications. In brief, anti-GFP antibody (Abcam) and protein A/G agarose beads (Roche) were used to precipitate the chromatin complex.…”

“…We have also isolated AhAREB1 (Arachis hypogaea ABA responsive element binding protein 1) from peanut and found that the AhAREB1 gene is specifically induced by ABA, dehydration, and drought . As for the possible role of the AhAREB1 transcription factor in the regulation of AhNCED1, Liu et al (2016a) demonstrated that the AhAREB1/AhNAC2 protein complex could negatively regulate the expression of AhNCED1. However, the regulation of AhAREB1 on AhNCED1 is not clear and the domain function of the AhAREB1 transcription factor also needs to be further confirmed.…”

Role of ABA Signaling in Regulation of Stem Sugar Metabolism and Transport under Post- Flowering Drought Stress in Sweet Sorghum

“…Some of the ABFs in turn regulate the expression of genes involved in ABA biosynthesis by binding to the ABA-responsive cis-elements (ABREs) present in the promoters of ABA biosynthesis genes and bring about higher ABA accumulation. For example, the activity of 9-cisepoxycarotenoid dioxygenase (NCED), which is a ratelimiting step in ABA biosynthesis, was reported to have two ABREs in its promoter and was subjected to regulation by ABFs, besides other transcription factors (Liu et al 2016). In the two sorghum lines studied, stress-induced ABA accumulation correlated to higher expression of the ABFs, in an ABA concentration-dependent manner.…”

Molecular background of cadmium tolerance in Rht dwarf wheat mutant is related to a metabolic shift from proline and polyamine to phytochelatin synthesis

“…Indeed, increased ABA content can increase NCED expression. According to these, an important regulatory mechanism of the actual ABA level is it hydroxylation and degradation (Liu et al 2016).…”