The role of small RNAs in abiotic stress.

It was recently discovered that plants respond to environmental stress not only with a specific gene expression programme at the mRNA and protein level but also small RNAs as response modulators play an important role. The small RNAs lead to cleavage or translational inhibition of mRNAs via complementary target sites. Different examples are described where small RNAs have been shown to be involved in stress responses. A link between hormonal action and small RNA activities has frequently been observed thus coupling exogenous factors with endogenous transmitters. Using the CDT-1 gene from the desiccation tolerant plant Craterostigma plantagineum as an example, it is discussed that generation of novel small RNAs could be an evolutionary pathway in plants to adapt to extreme environments.