Roles of miR319 and TCP Transcription Factors in Leaf Development

Abstract

Sophisticated regulation of gene expression, including microRNAs (miRNAs) and their target genes, is required for leaf differentiation, growth, and senescence. The impact of miR319 and its target <i>TEOSINTE BRANCHED1</i>, <i>CYCLOIDEA</i>, and <i>PROLIFERATING CELL NUCLEAR ANTIGEN BINDING FACTOR</i> (<i>TCP</i>) genes on leaf development has been extensively investigated, but the redundancies of these gene families often interfere with the evaluation of their function and regulation in the developmental context. Here, we present the genetic evidence of the involvement of the <i>MIR319</i> and <i>TCP</i> gene families in Arabidopsis (<i>Arabidopsis thaliana</i>) leaf development. Single mutations in <i>MIR319A</i> and <i>MIR319B</i> genes moderately inhibited the formation of leaf serrations, whereas double mutations increased the extent of this inhibition and resulted in the formation of smooth leaves. Mutations in <i>MIR319</i> and gain-of-function mutations in the <i>TCP4</i> gene conferred resistance against miR319 and impaired the cotyledon boundary and leaf serration formation. These mutations functionally associated with <i>CUP-SHAPED COTYLEDON</i> genes, which regulate the cotyledon boundary and leaf serration formation. In contrast, loss-of-function mutations in miR319-targeted and nontargeted <i>TCP</i> genes cooperatively induced the formation of serrated leaves in addition to changes in the levels of their downstream gene transcript. Taken together, these findings demonstrate that the <i>MIR319</i> and <i>TCP</i> gene families underlie robust and multilayer control of leaf development. This study also provides a framework toward future researches on redundant miRNAs and transcription factors in Arabidopsis and crop plants.