Identification of early Al‐responsive genes in rice bean (Vigna umbellata) roots provides new clues to molecular mechanisms of Al toxicity and tolerance

Abstract

Significant secretion of citrate from root apex of rice bean (Vigna umbellata) is delayed by several hours under aluminium (Al) stress. However, the molecular basis of regulation of VuMATE1, a gene encoding an Al-activated citrate transporter, remains unclear. In this study, we used suppression subtractive hybridization together with reverse northern blot analysis and qRT-PCR to identify genes with altered transcript levels in the root apex after treatment with low (5 μM) or high (25 μM) concentration of AlCl3 for a short time (4 h). We found that in addition to VuMATE1, 393 genes showed an early response to Al. Among functionally annotated genes, those related to 'metabolism and energy', 'signal transduction and transcription' and 'transport' was predominantly up-regulated, whereas those associated with 'protein translation, processing and degradation' was predominantly down-regulated. Comparative analysis of transcriptional profiles highlighted candidate genes associated with citrate secretion and revealed several new aspects of the molecular processes underlying Al toxicity and tolerance. Based on the data, it is proposed that metabolic changes represent adaptive mechanisms to Al stress, whereas inhibition of both cell elongation and cell division underlies Al-induced root growth inhibition.

An Oxalyl-CoA Synthetase Is Involved in Oxalate Degradation and Aluminum Tolerance

“…On the basis of rice bean root tip Al stress-responsive suppression subtractive hybridization libraries (Fan et al, 2014), we obtained a full-length VuAAE3 cDNA via rapid amplification of cDNA ends (RACE)-PCR method (GenBank accession no. KX354978; Supplemental Fig.…”

“…The potential of formate formation from oxalate catabolism led us to hypothesize whether this pathway exist in rice bean. More interestingly, a gene previously named as peroxisomal-coenzyme A synthetase (PCAS) was found to be up-regulated significantly in root apices of rice bean, and actually PCAS has high amino acid sequence homology with Arabidopsis AAE3 (Fan et al, 2014). Thus, it is likely that one possible route to formate accumulation originates from degradation of oxalate mediated by PCAS.…”

A Formate Dehydrogenase Confers Tolerance to Aluminum and Low pH

“…In this study, we isolated a full-length VuFDH cDNA, and found that the expression of VuFDH in rice bean root tips is enhanced greatly not only by Al (as previously shown; Fan et al, 2014) but also by low pH stress. We also showed that Al induces the rapid accumulation of formate in rice bean root apices, an accumulation that may contribute to Al-induced root growth inhibition.…”

“…For example, transcriptional profiling studies revealed that genes related to metabolism were differentially expressed in response to Al stress in Arabidopsis, rice (Oryza sativa), barrel clover (Medicago truncatula), maize (Zea mays), and rice bean [Vigna umbellata; Chandran et al, 2008;Kumari et al, 2008;Fan et al, 2014;Mattiello et al, 2014;Wang et al, 2014)]. In addition, proteomic analysis has indicated that proteins of metabolic function are differentially regulated in response to Al stress in roots of tobacco, soybean (Glycine max), and rice (Zhou et al, 2009;Zhen et al, 2007;Wang et al, 2014).…”

The roles of STOP1-like transcription factors in aluminum and proton tolerance

“…18,21 Either AtSTOP1 and AtSTOP2 in Arabidopsis or OsART1 in rice is constitutively expressed, 14,16,17 thus Al or H C regulates them posttranslationally, e.g. direct activation of protein activity.…”