Transcriptional profiling in cadmium-treated rice seedling roots using suppressive subtractive hybridization.

Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China.
Plant Physiology and Biochemistry (Impact Factor: 2.78). 08/2011; 50(1):79-86. DOI: 10.1016/j.plaphy.2011.07.015
Source: PubMed

ABSTRACT Cadmium (Cd), a non-essential metal, is a kind of toxic heavy metal to life, which can accumulate in rice tissues including seeds, thus posing a risk to human health through food chain. To investigate the molecular mechanisms of rice response to Cd exposure, suppression subtractive hybridization and mirror orientation selection were used to compare gene expression profiles in seedling roots of Cd-exposed and control (unexposed) rice plants (Oryza sativa L., Nipponbare). Approximately 1700 positive clones, with insertions ranging from 250 to 1300 bp, were identified through reverse cDNA microarray analysis. Gene expression was further confirmed by real time RT-PCR. A number of differentially expressed genes were found in Cd-exposed rice roots, including 28 up-regulated genes and 19 down-regulated genes. They were found to be involved in diverse biological processes, such as metabolism, stress response, ion transport and binding, protein structure and synthesis, as well as signal transduction. Notably a number of known functional genes were identified encoding membrane proteins and stress-related proteins such as heat shock proteins, monosaccharide transporters, CBL-interacting serine/threonine-protein kinases and metal tolerance proteins. The cDNAs isolated in this study contribute to our understanding of genes and the biochemical pathways that may play a key role in the response of plants to metal exposure in the environment.

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    ABSTRACT: Plant growth is severely affected by toxic concentrations of the non-essential heavy metal cadmium (Cd). Comprehensive transcriptome analysis by RNA-Seq following cadmium exposure is required to further understand plant responses to Cd and facilitate future systems-based analyses of the underlying regulatory networks. In this study, rice plants were hydroponically treated with 50 µM Cd for 24 hours and ∼60,000 expressed transcripts, including transcripts that could not be characterized by microarray-based approaches, were evaluated. Upregulation of various ROS-scavenging enzymes, chelators and metal transporters demonstrated the appropriate expression profiles to Cd exposure. Gene Ontology enrichment analysis of the responsive transcripts indicated the upregulation of many drought stress-related genes under Cd exposure. Further investigation into the expression of drought stress marker genes such as DREB suggested that expression of genes in several drought stress signal pathways was activated under Cd exposure. Furthermore, qRT-PCR analyses of randomly selected Cd-responsive metal transporter transcripts under various metal ion stresses suggested that the expression of Cd-responsive transcripts might be easily affected by other ions. Our transcriptome analysis demonstrated a new transcriptional network linking Cd and drought stresses in rice. Considering our data and that Cd is a non-essential metal, the network underlying Cd stress responses and tolerance, which plants have developed to adapt to other stresses, could help to acclimate to Cd exposure. Our examination of this transcriptional network provides useful information for further studies of the molecular mechanisms of plant adaptation to Cd exposure and the improvement of tolerance in crop species.
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