Genome-wide transcriptome and functional analysis of two contrasting genotypes reveals key genes for cadmium tolerance in barley

Abstract

BackgroundCadmium (Cd) is a severe detrimental environmental pollutant. To adapt to Cd-induced deleterious effects, plants have evolved sophisticated defence mechanisms. In this study, a genome-wide transcriptome analysis was performed to identify the mechanisms of Cd tolerance using two barley genotypes with distinct Cd tolerance.ResultsMicroarray expression profiling revealed that 91 genes were up-regulated by Cd in Cd-tolerant genotype Weisuobuzhi and simultaneously down-regulated or non-changed in Cd-sensitive Dong17, and 692 genes showed no change in Weisuobuzhi but down-regulated in Dong17. Novel genes that may play significant roles in Cd tolerance were mainly via generating protectants such as catalase against reactive oxygen species, Cd compartmentalization (e.g. phytochelatin-synthase and vacuolar ATPase), and defence response and DNA replication (e.g. chitinase and histones). Other 156 up-regulated genes in both genotypes also included those encoding proteins related to stress and defence responses, and metabolism-related genes involved in detoxification pathways. Meanwhile, biochemical and physiological analysis of enzyme (ATPase and chitinase), phytohormone (ethylene), ion distribution and transport (Cd, Na+, K+, Ca2+, ABC transporter) demonstrated that significantly larger Cd-induced increases of those components in Weisuobuzhi than those in Dong17. In addition, Cd-induced DNA damage was more pronounced in Dong17 than that in Weisuobuzhi.ConclusionsOur findings suggest that combining microarray, physiological and biochemical analysis has provided valuable insights towards a novel integrated molecular mechanism of Cd tolerance in barley. The higher expression genes in Cd tolerant genotype could be used for transgenic overexpression in sensitive genotypes of barley or other cereal crops for elevating tolerance to Cd stress.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-611) contains supplementary material, which is available to authorized users.

Cadmium localization and its toxic effects on root tips of barley

“…The results here supported our previous observation where cadmium was found to be absorbed within hours in the root cells of a Allium sativum exposed to cadmium ). Cao et al (2014), using Leadmium TM Green AM, found that preferential localization of cadmium was in root apex of the root tips of Cd-tolerant genotype 'Weisuobuzhi' in barley exposed to cadmium, suggesting that this effect was more pronounced with increasing cadmium concentration.…”

“…It has been already demonstrated that some chromosomal aberration may occur by non direct genotoxic effect. Cadmium is known to have indirect effects on DNA, causing strand breaks, sister chromatid exchanges, chromosomal aberrations (Cao et al, 2014;El-Habit, Moneim, 2014). Cadmium inhibited cell division and cell expansion growth, resulting in inhibition of root growth and appearance of stunted roots (Zhang et al, 2009).…”

“…Cadmium inhibited cell division and cell expansion growth, resulting in inhibition of root growth and appearance of stunted roots (Zhang et al, 2009). Some damage induced by cadmium can inhibit DNA repair mechanisms by competition with certain ions which are essential for DNA polymerases (Cao et al, 2014).…”

Alleviation of cadmium toxicity in cucumber (Cucumis sativus) seedlings by the application of selenium

“…Once in plants, Cd can bring a host of biochemical and physiological consequences. Cd-accrued inhibited photosynthesis and impaired growth have been reported in several plants including barley, cucumber (Gallego et al, 2012;Janicka-Russak et al, 2012;Cao et al, 2014a;Asgher et al, 2015). Cd is a non-redox active metal, it can induce generation of reactive oxygen species (ROS), lead to the oxidative burst.…”

Proteomic analysis of saffron (Crocus sativus L.) grown under conditions of cadmium toxicity

“…Cd affects many important physiological and biochemical processes in plants such as photosynthesis and nutrient homeostasis, which in turn inhibits normal plant growth and development (CLIJSTERS;VANASSCHE, 1985;CAO et al, 2014b). To defend against the detrimental effects of Cd, plants have evolved many detoxification mechanisms, including Cd chelation and vacuolar compartmentalization (HALL, 2002).…”