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.
Highlights
Cadmium (Cd) is a severe detrimental environmental pollutant
Cd is highly accumulated in root tips of a Cd-tolerant genotype Under Cd stress, the majority of Cd accumulated in root cell wall
In root tips of Weisuobuzhi treated with 5 μM Cd, preferential localisation of Cd was in root apex, and this effect was more pronounced with increasing Cd levels (Figure 1A and 1C)
Summary
Cadmium (Cd) is a severe detrimental environmental pollutant. To adapt to Cd-induced deleterious effects, plants have evolved sophisticated defence mechanisms. Cd has become one of the most harmful and widespread pollutants in agricultural soils This situation has resulted primarily from industrial emissions, application of Cd containing phosphate fertilisers and municipal waste disposal [1,3]. To minimise the detrimental effects of Cd toxicity, plants have evolved a range of detoxification mechanisms, including Cd exclusion, chelation and compartmentalisation in vacuoles [6]. Phytochelatins (PCs) and Cd have been found to form PC-Cd complexes in cytosol, which are subsequently transported into vacuoles. Thereby, it can protect plants from the deleterious effects of Cd [7]. Regulatory mechanisms in Cdtolerance, which is still a focal point in plant research, is a complex process that contains many genes regulated by a variety of physiological pathways [2]
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