Leaf shape is an important agronomic trait that is involved in plant photosynthesis, flowering, disease resistance, and yield. In recent years, many leaf shape-related genes have been identified in model plants, but the precise regulatory network of leaf shape development remains unclear, particularly in woody plants. Transcriptome analysis of trifoliate orange and lemon leaves revealed that two citrus Knotted1-like (CiKN1 and CiKN6) genes might participate in leaf development. Overexpression of CiKN1 displays lobed leaves in simple leaf Arabidopsis and lemon. Further protein interaction analysis revealed that CiKN6 interacted with CiKN1, whose overexpression resulted in deeper lobed leaves in transgenic Arabidopsis and lemon. Suppressing CiKN6 expression also affected the development of lemon leaves. Furthermore, we found that the CiKN1-CiKN6 complex specifically binds to the citrus miR164a promoter and suppresses its expression. In addition, a SQUAMOSA promoter binding protein-like (SPL) gene (CiSPL11) was identified using yeast one-hybrid assays and was found to promote CiKN6 transcription by binding to its promoter. Transgenic Arabidopsis showed that CiSPL11 might be involved in the development of citrus leaves. These results suggested that the CiKN1-CiKN6 complex and miR164a interact to regulate leaf development in citrus.
Keywords: KNAT; SQUAMOSA promoter binding protein, miR164; citrus; leaf development.