Genomic stability in Nicotiana plants upon silencing of the mismatch repair gene MSH2
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The Mismatch Repair (MMR) system is a highly conserved pathway for the maintenance of genomic stability in many organisms. In plants, this is particularly important because of the lack of a reserved germline. Suppression of MMR leads to an accumulation of random mutations in the genome over successive generations, and thus maximizes genetic diversity. MMR deficiency has been shown to be a useful technique in plant breeding, complementary to chemical or physical mutagenesis. We have developed an artificial microRNA (amiRNA) targeting the MSH2 gene, which is generally applicable in Solanaceae. Two amiRNA precursors were inserted in a transformation vector, under the control of the CaMV 35S promoter and the meiosis active AtDMC1 promoter, respectively. Introduction of this amiRNA construct in Nicotiana tabacum and N. plumbaginifolia reduced the MSH2 transcript levels to 20–30 %. Morphological and developmental abnormalities and plants with white sectors on the first pair of leaves or on the cotyledons (referred to as ‘chimeric albinos’) appeared in the transformed Nicotiana lines at higher frequencies than in the control lines. Also, some plants which show an increased tolerance for the herbicide chlorsulfuron were found. However, the mutant phenotypes were not transmitted to subsequent generations. We conclude that the designed amiRNA was capable of suppressing the MSH2 activity, which caused the occurrence of somatic mutations. Apparently, the silencing of MSH2 was not strong enough in the germline to cause inheritable mutations.
KeywordsMismatch repair MSH2 Mutagenesis Nicotiana Solanum tuberosum
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