Identification of the role of BLH genes in plant leaf morphogenesis

Jeon HW and Byrne M

School of Biological Sciences, The University of Sydney, Sydney, NSW, Australia.

Plant leaves are one of the most obvious features of plants. After the initiation from the shoot apical meristem, they form diverse leaf shapes determined by leaf morphogenesis. Arabidopsis thaliana, a model of plant biology, has two families of the transcription factor, BEL1-LIKE TALE HOMEODOMAIN (BLH) proteins and KNOTTED1-LIKE TALE HOMEOBOX (KNOX) proteins, that affect various plant aspects as well as leaf development. First, among a total of thirteen BLH proteins, previous studies have shown that BLH2/SAW1 and BLH4/SAW2 are redundantly required for leaf margin development. Second, class II KNOX proteins (KNAT3, 4, 5) have been identified as regulators of the above-ground organ development including leaf formation. In addition to these transcription factors, an auxin-CUC2 feedback loop is a well-known hormonal mechanism that regulates the shape of leaf margins. To understand how plants determine their leaf shape, our study is aiming at the in-depth characterisation of SAW proteins with their functional redundancies and the relationship between BLH and KNOX in terms of the leaf margin development as well as how these proteins interact with the auxin-CUC2 regulation module. We have found that additional knockout of a class II KNOX gene in saw1 saw2 double mutants can enhance the leaf serration phenotype. This observation leads to the possibility of the new BLH-KNOX interactions in leaf shape formation. Consequently, our study will provide an insight into the underlying mechanisms of the leaf development with a better understanding of BLH and KNOX functions.