Abstract
Cadmium (Cd) is a non-essential heavy metal that is toxic to plants. microRNAs (miRNAs) are 21-nucleotide RNAs that are ubiquitous regulators of gene expression at the post-transcriptional level. Several plant miRNAs, such as miR390, have vital roles in plant growth, development and responses to environmental stresses including heavy metal stress. In this study, the expression of mature miR390 was significantly down-regulated under Cd stress in rice. Consequently, the target gene of miR390, OsSRK was dramatically induced by Cd treatment. Transgenic rice plants overexpressing miR390 displayed reduced Cd tolerance and higher Cd accumulation compared with wild-type plants. Simultaneously, expression of OsSRK was less pronounced in 35S:MIR390 plants than in wild-type. These results indicate that miR390 was a negative regulator involved in Cd stress tolerance in rice.
Highlights
Cadmium is an important environmental pollutant that is highly toxic to plants (Schützendübel et al, 2001)
Rice miRNA expression patterns were examined under Cd stress using a microarray assay containing probes complementary to the miRNA sequences in miRBase Release 11.04 (Ding et al, 2011). 1-week-old rice seedlings were treated with 60 μM CdCl2 for 6 h, after which small RNA was isolated from roots and used to screen the microarray
Mature miR390 expression was down-regulated after 6 h exposure to 60 μM CdCl2, which was consistent with the microarray data (Figure 1B)
Summary
Cadmium is an important environmental pollutant that is highly toxic to plants (Schützendübel et al, 2001). It is widely released into soil, air, and water mainly by effluent from industrial sources, mining, and phosphate fertilization (Pinto et al, 2004). Cd is readily taken up by plants, resulting in toxic symptoms. It damages the photosynthetic apparatus, decreases carbon assimilation and chlorophyll content, and eventually leads to wilting and plant death (Hsu and Kao, 2003; Rodriguez-Serrano et al, 2009). In plants, increasing reports have demonstrated that miRNAs have vital regulatory roles in growth, development and plant resistance to abiotic and biotic stresses, including heavy metal stress (Sunkar et al, 2006; Ding and Zhu, 2009; Khraiwesh et al, 2012)
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