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Genome-wide transcriptome analysis reveals that cadmium stress signaling controls the expression of genes in drought stress signal pathways in rice.

Oono Y, Yazawa T, Kawahara Y, Kanamori H, Kobayashi F, Sasaki H, Mori S, Wu J, Handa H, Itoh T, Matsumoto T - PLoS ONE (2014)

Bottom Line: Plant growth is severely affected by toxic concentrations of the non-essential heavy metal cadmium (Cd).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.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.

View Article: PubMed Central - PubMed

Affiliation: Agrogenomics Research Center, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan.

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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Related in: MedlinePlus

Rice phenotypes under Cd exposure.Phenotypic changes in rice plants grown from 0 to 120 h in culture medium with 50 µM CdSO4 for Cd stress. The shoots showed growth retardation. Black spots on the leaves gradually increased and leaves curled up slowly during Cd exposure. RPKM fold changes at 1 h and 24 h were calculated for Cd treated samples compared with non-treated samples (0 h).
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pone-0096946-g001: Rice phenotypes under Cd exposure.Phenotypic changes in rice plants grown from 0 to 120 h in culture medium with 50 µM CdSO4 for Cd stress. The shoots showed growth retardation. Black spots on the leaves gradually increased and leaves curled up slowly during Cd exposure. RPKM fold changes at 1 h and 24 h were calculated for Cd treated samples compared with non-treated samples (0 h).

Mentions: In the hydroponically cultured rice, growth was greatly affected by Cd exposure (Figure 1). In Cd-exposed rice, growth retardation of the shoot was apparent after 24 h, many dark spots appeared on all leaves after 48 h, the leaves turned yellow and the leaf tips of the seedlings began to wilt after 72 h, and after 120 h of 50 µM cadmium exposure all leaf blades were curled completely and the seedlings were shrunken and wilting, which is attributable to supply of Cd (Figure 1). This concentration or higher concentrations of Cd have been previously shown to elicit robust physiological responses and gene expression as acute toxic responses in rice seedlings [3], [30], [31]. The wilting occurred gradually compared with drought treatment for 24 h, in which symptoms started to appear after 2 h treatment and plants were completely dried up after 24 h, in the same growth chamber (Figure S1). The detoxification processes of the plant are insufficient to cope with the toxic metal beyond a 10 µM dose, and wilting and reduction of plant fresh weight are accompanied by decreased leaf conductance and increased stomatal closing [32]. It has been suggested that part of the fatal damage to plants from Cd exposure occurs through drought stress.


Genome-wide transcriptome analysis reveals that cadmium stress signaling controls the expression of genes in drought stress signal pathways in rice.

Oono Y, Yazawa T, Kawahara Y, Kanamori H, Kobayashi F, Sasaki H, Mori S, Wu J, Handa H, Itoh T, Matsumoto T - PLoS ONE (2014)

Rice phenotypes under Cd exposure.Phenotypic changes in rice plants grown from 0 to 120 h in culture medium with 50 µM CdSO4 for Cd stress. The shoots showed growth retardation. Black spots on the leaves gradually increased and leaves curled up slowly during Cd exposure. RPKM fold changes at 1 h and 24 h were calculated for Cd treated samples compared with non-treated samples (0 h).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4016200&req=5

pone-0096946-g001: Rice phenotypes under Cd exposure.Phenotypic changes in rice plants grown from 0 to 120 h in culture medium with 50 µM CdSO4 for Cd stress. The shoots showed growth retardation. Black spots on the leaves gradually increased and leaves curled up slowly during Cd exposure. RPKM fold changes at 1 h and 24 h were calculated for Cd treated samples compared with non-treated samples (0 h).
Mentions: In the hydroponically cultured rice, growth was greatly affected by Cd exposure (Figure 1). In Cd-exposed rice, growth retardation of the shoot was apparent after 24 h, many dark spots appeared on all leaves after 48 h, the leaves turned yellow and the leaf tips of the seedlings began to wilt after 72 h, and after 120 h of 50 µM cadmium exposure all leaf blades were curled completely and the seedlings were shrunken and wilting, which is attributable to supply of Cd (Figure 1). This concentration or higher concentrations of Cd have been previously shown to elicit robust physiological responses and gene expression as acute toxic responses in rice seedlings [3], [30], [31]. The wilting occurred gradually compared with drought treatment for 24 h, in which symptoms started to appear after 2 h treatment and plants were completely dried up after 24 h, in the same growth chamber (Figure S1). The detoxification processes of the plant are insufficient to cope with the toxic metal beyond a 10 µM dose, and wilting and reduction of plant fresh weight are accompanied by decreased leaf conductance and increased stomatal closing [32]. It has been suggested that part of the fatal damage to plants from Cd exposure occurs through drought stress.

Bottom Line: Plant growth is severely affected by toxic concentrations of the non-essential heavy metal cadmium (Cd).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.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.

View Article: PubMed Central - PubMed

Affiliation: Agrogenomics Research Center, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan.

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.

Show MeSH
Related in: MedlinePlus