Rice ABI5-Like1 Regulates Abscisic Acid and Auxin Responses by Affecting the Expression of ABRE-Containing Genes    

Abstract

Abscisic acid (ABA) regulates plant development and is crucial for plant responses to biotic and abiotic stresses. Studies have identified the key components of ABA signaling in Arabidopsis (Arabidopsis thaliana), some of which regulate ABA responses by the transcriptional regulation of downstream genes. Here, we report the functional identification of rice (Oryza sativa) ABI5-Like1 (ABL1), which is a basic region/leucine zipper motif transcription factor. ABL1 is expressed in various tissues and is induced by the hormones ABA and indole-3-acetic acid and stress conditions including salinity, drought, and osmotic pressure. The ABL1 deficiency mutant, abl1, shows suppressed ABA responses, and ABL1 expression in the Arabidopsis abi5 mutant rescued the ABA sensitivity. The ABL1 protein is localized to the nucleus and can directly bind ABA-responsive elements (ABREs; G-box) in vitro. A gene expression analysis by DNA chip hybridization confirms that a large proportion of down-regulated genes of abl1 are involved in stress responses, consistent with the transcriptional activating effects of ABL1. Further studies indicate that ABL1 regulates the plant stress responses by regulating a series of ABRE-containing WRKY family genes. In addition, the abl1 mutant is hypersensitive to exogenous indole-3-acetic acid, and some ABRE-containing genes related to auxin metabolism or signaling are altered under ABL1 deficiency, suggesting that ABL1 modulates ABA and auxin responses by directly regulating the ABRE-containing genes.

Characterization of OsPM19L1 encoding an AWPM-19-like family protein that is dramatically induced by osmotic stress in rice

“…Based on the observation that OsPM19L1 was dramatically induced by ABA treatment, it may play an important role in ABA signaling. The ABL1 protein is localized to the nucleus and modulates the plant stress and ABA responses by directly regulating the ABRE-containing genes (Yang et al, 2011). An ABRE protein binding site in the promoter region of OsPM19L1 suggests that OsPM19L1 may participate in plant stress and ABA responses under the regulation of ABL1 transcription factor.…”

“…The rice (Oryza sativa L. ssp japonica) cultivars Jiucaiqing, Zhonghua11 (ZH11), and abl1 mutant of Zhonghua11 (Yang et al, 2011) were used in this study. The seeds were sterilized in 0.1% HgCl 2 and germinated at 30°C.…”

“…The rice ABI5-like1 (ABL1) deficiency mutant, abl1, shows suppressed ABA responses (Yang et al, 2011). Since previous data suggest that OsPM19L1 expression is regulated by ABA treatment, it was of interest to analyze whether OsPM19L1 was involved in ABL1 signaling pathway.…”

“…Since there is limited insight into the specificity of rice signaling, studies on rice ABA signal transduction will be very valuable to elucidate the functional mechanism of ABA. Rice ABI5-Like1 (ABL1), a basic region/leucine zipper motif transcription factor, modulates ABA responses by directly regulating the ABA-responsive element (ABRE)-containing genes (Zou et al, 2007(Zou et al, , 2008Yoshida et al, 2010;Yang et al, 2011).…”

A systems biology perspective on the role of WRKY transcription factors in drought responses in plants

“…Yang et al (2011) have shown that rice ABI5-Like1 (ABL1) regulates ABA and auxin responses through ABRe-containing wRKY genes. OsWRKY69 has an ABRe element in its promoter that leads to specific binding of the bZIP transcription factor (ABL1), which suppresses auxin signaling while enhancing ABA signaling and hence provides insights into ABA and auxin crosstalk ).…”