Tiny RNAs behind plant stress sensitivity
doi:10.1038/nindia.2012.182 Published online 12 December 2012
New research has linked a mutation in a gene of Arabidopsis that codes for SICKLE (SIC) protein to lower levels of cellular microRNAs (miRNAs), a type of tiny RNA molecule. The lower levels of miRNA molecules make the plant sensitive to environmental stresses like chilling and salinity, and lead to developmental defects such as stunted growth and delayed flowering.
Such insights into links between genetic mutation, reduced levels of miRNA and flawed developments could yield new ways to genetically engineer plants to tolerate environmental stresses.
Although the roles of miRNAs in plant development and stress responses are well known, no studies have comprehensively linked the roles of proteins such as SIC to miRNA biogenesis and environmental stress responses.
In the hope of finding such links in plants, the researchers induced mutations in the Arabidopsis genome using ethane methyl sulfonate, a mutagen and carcinogen. This yielded a sickle-1 (sic-1) mutant variety of Arabidopsis with a mutation in the SIC gene. They also exposed sic-1 plants to cold stress at four degrees Celsius, plant stress hormone and salt stress using sodium chloride, then compared sic-1's stress responses with those of normal Arabidopsis plants.
In addition to delayed flowering and dwarfism compared with normal plants, the sic-1 mutant was sensitive to cold stress and showed lower levels of miRNAs in vegetative and reproductive tissues. The sickle leaf margin of sic-1 mutant plants was corrected in transgenic plants expressing the normal SIC gene, supporting the idea that SIC is necessary for normal plant development.
"This suggests the possibility of controlling the expression of a set of genes required for a specific stress tolerance by engineering the accessory small RNA biogenesis factors such as SICKLE protein," says Viswanathan Chinnusamy, one of the researchers.
The authors of this work are from: Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, Shanghai, China; Purdue University, West Lafayette, University of California, Riverside, US; Central Arid Zone Research Institute, Jodhpur, and Division of Plant Physiology, Indian Agricultural Research Institute, New Delhi, India.