Development of Tos17 insertion mutants from Korean cultivars "Ilmibyeo' and "Baegjinju1ho' (Oryza sativa L.)

Rice is one of the most important crops globally and a model plant for genomic studies of monocots. With the release of complete genome sequences, the next challenge is to develop various resources based on functional analyses of genes. In this study, we generated mutants via the insertion of Tos17, a mobile endogenous retrotransposon active during tissue culture. Two rice cultivars, Oryza sativa L. japonica Ilmibyeo' (IM) and Baegjinju1ho' (BJJ1), which represent white and brown rice in the Korean domestic market, respectively, were selected for this study. We analyzed 7608 flanking sequences of newly transposed Tos17 insertions by the flanking adaptor-ligation polymerase chain reaction method and identified 1672 and 843 mutants (M-2 generation) in IM and BJJ1, respectively. An analysis of these Tos17 insertions showed the preferential insertion of Tos17 into rice chromosome genic regions (approximately 70%). We found new insertional mutants in 830 genes among the 1533 genes representing 2515 IM and BJJ1 mutants that did not overlap with the 3280 genes affected in the Nipponbare' (NP) mutants from the National Institute of Agrobiological Sciences database. Of the 1000 lines of Tos17 insertion mutants, we observed semi-dwarf and various leaf-type mutants, including those with narrow, pale-green, and striped leaves at the vegetative stage. At the reproductive stage, 10 lines showed a 17-56% increase in 100-grain weight compared with the wild type. This study demonstrates the potential utility of Tos17 mutants via an efficient tissue culture method in various rice cultivars for improving agronomic traits, including seed weight.