The role of VuMATE1 expression in aluminium-inducible citrate secretion in rice bean (Vigna umbellata) roots

Abstract

Aluminium (Al)-activated citrate secretion plays an important role in Al resistance in a number of plant species, such as rice bean (Vigna umbellata). This study further characterized the regulation of VuMATE1, an aluminium-activated citrate transporter. Al stress induced VuMATE1 expression, followed by the secretion of citrate. Citrate secretion was specific to Al stress, whereas VuMATE1 expression was not, which could be explained by a combined regulation of VuMATE1 expression and Al-specific activation of VuMATE1 protein. Pre-treatment with a protein translation inhibitor suppressed VuMATE1 expression, indicating that de novo biosynthesis of proteins is required for gene expression. Furthermore, post-treatment with a protein translation inhibitor inhibited citrate secretion, indicating that post-transcriptional regulation of VuMATE1 is critical for citrate secretion. Protein kinase and phosphatase inhibitor studies showed that reversible phosphorylation was important not only for transcriptional regulation of VuMATE1 expression but also for post-translational regulation of VuMATE1 protein activity. These results suggest that citrate secretion is dependent on both transcriptional and post-transcriptional regulation of VuMATE1. Additionally, VuMATE1 promoter–β-glucuronidase fusion lines revealed that VuMATE1 expression was restricted to the root apex and was entirely Al induced, indicating the presence of cis-acting elements regulating root tip-specific and Al-inducible gene expression, which will be an important resource for genetic improvement of plant Al resistance.

Expression of cytochrome P450 CYP81A6 in rice: tissue specificity, protein subcellular localization, and response to herbicide application

“…These results indicate that CYP81A6 expression is up-regulated by a protein (probably a transcription factor) that is translated de novo and is directly or indirectly induced by bentazon; they also rule out the possible involvement of a repressor protein suppressing its transcription in the absence of bentazon. A similar phenomenon was reported in rice bean on the Al-induced expression of VuMATE1 (Liu et al, 2013).…”

“…Three-week-old seedlings (about 18 cm long with 4 leaves) were sprayed with the herbicides bentazon, metsulfuron-methyl, or pendimethalin at a range of concentrations (0, 250, 500, 1000, and 1500 mg/L). The effect of the protein translation inhibitor cycloheximide (CHX) on CYP81A6 expression was tested by spraying 20 µmol/L CHX 1 h before bentazon treatment (500 mg/L), as performed in rice bean by Liu et al (2013).…”

Isolation and Characterization of an Aluminum-resistant Mutant in Rice

“…A number of plant species are documented to secrete different organic acids to detoxify Al. For instance, wheat ( Triticum aestivum ), Arabidopsis thaliana and oilseed rape ( Brassica napus ) release malate for Al detoxification (Delhaize et al 1993; Ligaba et al 2006; Hoekenga et al 2003), whereas snapbean ( Phaseolus vulgaris ), rice bean ( Vigna umbellata ), maize ( Zea mays ), and soybean ( Glycine max ) secrete citrate to detoxify Al (Miyasaka et al 1991; Pellet et al 1995; Yang et al 2000; Liu et al 2013; Yang et al 2006). Oxalate is exuded from roots of buckwheat, tomato and spinach ( Spinacia oleracea ) under Al stress (Ma et al 1997; Zheng et al 1998; Yang et al 2005; Yang et al 2011).…”

Alleviation by abscisic acid of Al toxicity in rice bean is not associated with citrate efflux but depends on ABI5‐mediated signal transduction pathways

“…Sequence alignment established that CL3862.Contig1_All and Unigene20395_All are VuMATE1 and VuMATE2 , respectively, two previously identified Al tolerance genes responsible for Al‐stimulated citrate efflux (Liu et al ; ). In line with our previous work, ABA could slightly induce VuMATE1 expression, but both the intensity and localization of the expression differed from that induced by Al (Liu et al ).…”