Improving panicle exsertion of rice cytoplasmic male sterile line by combination of artificial microRNA and artificial target mimic

The adoption of hybrid rice caused the second leap in rice yield after the green revolution' and contributes substantially to food security of China and the world. However, almost all cytoplasmic male sterile lines (A lines) as females of hybrid rice have a natural deficiency of panicle enclosure', which blocks pollination between the A line and the fertility restorer line as the male (R line) of hybrid rice and decreases seed yield. In hybrid rice seed production, exogenous 920' (the active ingredient is gibberellin A3) must be applied to eliminate or alleviate panicle enclosure of the A line; however, this not only increases production cost and pollutes the environment, it also decreases seed quality. In this study, we designed a transgenic approach to improve plant height and panicle exsertion of the A line to facilitate hybrid rice production and maintain the semi-dwarf plant type of the hybrid. This approach comprising two componentsartificial microRNA (amiRNA) and artificial target mimicrycan manipulate the differential expression of the endogenous Eui1 gene that is associated with rice internode elongation in the A line and the hybrid. amiRNA is a recently developed gene silencing method with high specificity, while target mimicry is a natural mechanism inhibiting the miRNA function that was also recently characterized. This approach provides a paradigm to tune the expression of endogenous genes to achieve the desired phenotype by combining amiRNA and artificial target mimicry technologies.