Rice ASR1 and ASR5 are complementary transcription factors regulating aluminium responsive genes

Abstract

Rice is the most tolerant staple crop to aluminium (Al) toxicity, which is a limiting stress for grain production worldwide. This Al tolerance is the result of combined mechanisms that are triggered in part by the transcription factor ASR5. ASRs are dual target proteins that participate as chaperones in the cytoplasm and as transcription factors in the nucleus. Moreover, these proteins respond to biotic and abiotic stresses, including salt, drought and Al. Rice plants with silenced ASR genes are highly sensitive to Al. ASR5, a well-characterized protein, binds to specific cis elements in Al responsive genes and regulates their expression. Because the Al sensitive phenotype found in silenced rice plants could be due to the mutual silencing of ASR1 and ASR5, we investigated the effect of the specific silencing of ASR5. Plants with artificial microRNA silencing of ASR5 present a non-transformed phenotype in response to Al because of the induction of ASR1. ASR1 has the same subcellular localization as ASR5, binds to ASR5 cis-regulatory elements, regulates ASR5 regulated genes in a non-preferential manner and might replace ASR5 under certain conditions. Our results indicate that ASR1 and ASR5 act in concert and complementarily to regulate gene expression in response to Al.

SiASR4, the Target Gene of SiARDP from Setaria italica, Improves Abiotic Stress Adaption in Plants

“…ASR proteins play important roles in abiotic stress tolerance in most plants, as observed for OsASR1, ZmASR1 , and TaASR1 (Virlouvet et al, 2011; Hu et al, 2013; Arenhart et al, 2016). SiASR4 , which is reported herein, was also found to enhance abiotic stress resistance in transgenic plants.…”

“…SbASR1 can reduce the accumulation of H 2 O 2 and ${\text{O}}_2^{.-}$ radicals and induce the transcription of ROS scavenger-associated genes (Tiwari et al, 2015). The rice ASR gene OsASR5 binds to cis elements in the promoters of aluminum-responsive genes and regulates the expression of these genes (Arenhart et al, 2016). The transcription levels of some ABA/stress-responsive genes decrease in transgenic plants carrying the lily ASR gene LLA23 , suggesting that LLA2 3 acts as a transcription factor mediating stress-responsive ABA signaling (Yang et al, 2005).…”

Expression patterns and promoter analyses of aluminum-responsive NAC genes suggest a possible growth regulation of rice mediated by aluminum, hormones and NAC transcription factors

“…Importantly, we found scarce evidence of the molecular mechanisms involving NAC transcription factors in direct response to Al toxicity, since neither cis -acting elements nor putative motifs previously reported [15] were found in the promoter regions of NAC genes here analyzed. Indeed, the corresponding consensus sequence () present in the Al-responsive gene promoters like ASR1 and ASR2 in rice [17] was not identified in our promoter analysis. Regardless, the present findings suggest consistency in the response of the NAC gene promoters to phytohormones, which suggests that these molecules can act as intermediaries in growth induction promoted by low concentrations of Al (hormetic effect).…”

“…In this study we also included the genes OsNAC6 [45], OsNAC5 [46], and OsNAC10 [47]. Furthermore, three control genes were also taken into consideration for the tests, which are known to respond to Al: STAR1 , ASR5 [15,17,48], and OsNAC5 [18]. The reference genes evaluated were actin , actin 1 , β-tubulin , and elongation factor 1α .…”

“…The ASR genes ( ASR1 and ASR5 ) are one of the pivotal components in the Al toxicity response machinery, as they codify transcription factors in rice, but they are absent in Arabidopsis [14]. When rice is exposed to toxic levels of Al, the ASR transcription factors act concertedly and complementarily, recognizing the cis -acting elements in the promoters of the STAR1 gene to potentiate the Al response expression of a set of target genes [15–17]. Another family of transcription factors that responds to Al is NAC [1,18], which are specific to plants [19–21].…”