Functional Characterization Of MiR160 In Cotton Ovule Development

The microRN A(miRNA) is a 21–24 nucleotide single stranded non-protein-coding RN A, which plays an important role on plant development, hormone signal transduction, morphogenesis, biotic and abiotic stress responses. Recently, a lot of researches about miRNA have been reported in Arabidopsis and other plants. However, there is less study about miRN A functions in cotton. In this study, the miR160 function in cotton ovule development will be explored.Ten miR160 precursors, which encode the same mature miRNA sequences, have been predicted by bioinformatics referring to the Gossypium hirsutum TM-1 genome. And then 16 potential miR160 target genes were predicted, which were the homologous genes to Auxin Response Factors ARF10, ARF16, ARF17 in Arabidopsis. The expression profile analysis in two cotton species of Gossypium hirsutum TM-1 and YZ1 showed that miR160 was preferentially expressed in ovule from-3 DPA to 0 DPA(days post anthesis), and the expression levels of target ARFs were negatively correlated with it during the development of ovule, suggesting that miR160 was involved in the development of cotton ovule. In order to explore the function of miR160 in ovule development, the mimicry vectors driven by ovule-coat-specific promoter FBP7 were constructed to develop genetically modified cotton lines. In FBP7::Mimicry160 lines, the bolls and seeds were smaller than negative control. Cotton fiber quality analysis data showed that the fiber length, lint index and seed index were less than negative control. Additionally, cotton ovule paraffin section analysis showed that the size of inner ovule epidermis cells was smaller than that of negative control. The relative expression level of ARF was increased in FBP7::Mimicry160 transgenic lines, suggesting that miR160 participated in the cotton ovule development via negative regulating the expression of target ARF. At the same time, we also constructed the overexpression transgenic cotton of miR160 of Arabidopsis driven by FBP7 promoter, however, there was no increased expression of miR160 and no significant phenotype difference in the FBP7::AtmiR160 transgenic lines compared to the negative control.