MAN3 gene regulates cadmium tolerance through the glutathione‐dependent pathway in Arabidopsis thaliana

Abstract

Summary Pollution of soil by the heavy metal cadmium (Cd) is a global environmental problem. The glutathione (GSH)‐dependent phytochelatin (PC) synthesis pathway is one of the most important mechanisms contributing to Cd accumulation and tolerance. However, the regulation of this pathway is poorly understood. Here, we identified an Arabidopsis thaliana cadmium‐tolerant dominant mutant xcd1‐D (XVE system‐induced cadmium‐tolerance 1) and cloned XCD1 gene (previously called MAN3), which encodes an endo‐β‐mannanase. Overexpression of MAN3 led to enhanced Cd accumulation and tolerance, whereas loss‐of‐function of MAN3 resulted in decreased Cd accumulation and tolerance. In the presence of estradiol, enhanced Cd accumulation and tolerance in xcd1‐D was associated with GSH‐dependent, Cd‐activated synthesis of PCs, which was correlated with coordinated activation of gene expression. Cd stress‐induced expression of MAN3 and the consequently increased mannanase activity, led to increased mannose content in cell walls. Moreover, mannose treatment not only rescued the Cd‐sensitive phenotype of the xcd1‐2 mutant, but also improved the Cd tolerance of wild‐type plants. Significantly, this mannose‐mediated Cd accumulation and tolerance is dependent on GSH‐dependent PC concentrations via coordinated control of expression of genes involved in PC synthesis. Our results suggest that MAN3 regulates the GSH‐dependent PC synthesis pathway that contributes to Cd accumulation and tolerance in A. thaliana by coordinated control of gene expression.

Zinc-Finger Transcription Factor ZAT6 Positively Regulates Cadmium Tolerance through the Glutathione-Dependent Pathway in Arabidopsis

“…In addition, a lot of key genes have been shown to be involved in Cd detoxification and tolerance in plants. These include ZNT1, OsHMA9, OsNRAMP5, ZntA, CAD2, AtPDR12, AtPDR8, AtATM3, ACBP1, Nramp5, EIN2, and MAN3 (Pence et al, 2000;Sharma et al, 2000;Shiraishi et al, 2000;Lee et al, 2003Lee et al, , 2007Kim et al, 2006Kim et al, , 2007Xiao et al, 2008;Cao et al, 2009;Lin and Aarts, 2012;Sasaki et al, 2012;Ishikawa et al, 2012;Chen et al, 2015). It was also found that Heat shock transcription factor A4a (HsfA4a) confers Cd tolerance by up-regulating MT gene expression in wheat (Triticum aestivum) and rice (Oryza sativa; Shim et al, 2009).…”

“…The xcd2-D mutant was screened as reported before (Chen et al, 2015). The XVE T-DNA-tagged genomic sequence in xcd2-D was identified by TAIL-PCR (Liu et al, 1995;Zuo et al, 2000;Sun et al, 2003) and DNA sequencing.…”

“…Digested samples were analyzed using an atomic absorption spectrometer (Solaar M6; Thermo Fisher). GSH/GSSG/PC were extracted from seedlings and quantitated according to previous report (Chen et al, 2015).…”

“…To screen for Cd-resistant mutants, we undertook a gain-of-function genetic screen (Chen et al, 2015) and isolated several putative mutants from the XVE-tagging T-DNA insertion lines (Zhang et al, 2005). One of these mutants, designated xcd2-D (XVE system-induced cadmiumtolerance2), was chosen for detailed analysis.…”

Diferentes abordagens para o estudo da resposta de solanáceas ao Cd

“…Diferentemente de alguns metais como o níquel (Ni) e zinco (Zn), que em baixas concentrações estimulam o crescimento da planta (BAZIHIZINA et al 2015), o Cd não está envolvido com nenhuma função fisiológica conhecida e existem inúmeros estudos demonstrando seu efeito deletério nas plantas (CHEN et al, 2015). Em nível celular e molecular a toxicidade por Cd pode influenciar no ciclo do nitrogênio e suas moléculas dependentes, inativando ou denaturando proteínas, podendo ocasionar peroxidação lipídica, ou seja, danos a membranas celulares, resultando na indução de estresse oxidativo, aberrações cromossômicas, e alterações na divisão e ciclo celular (LIN; AARTS, 2012; PIZZAIA, 2013).…”