Elucidating the Role of BLH Homeodomain Transcription Factors in Arabidopsis thaliana Leaf Development

Abstract

Leaves account for a considerable portion of the morphological diversity that is seen in the kingdom Plantae. Their shapes are informed by patterns of differential growth that are generated along the adaxial-abaxial, proximodistal, and mediolateral axes of development. Much of the variation in leaf shape is found around the leaf margin. Margin forms are diverse and span a range of shapes from smooth edges to those that are decorated with tooth-like serrations and/or leaflets. Although it may seem an obscure developmental feature, significant strides have been made into understanding the genetic regulation of the leaf margin in the past three decades. This work has, in turn, provided a useful platform to interrogate the molecular basis of shape evolution in plants.

Three amino acid loop extension (TALE) homeodomain transcription factors are a conserved protein superfamily characterised by their atypical homeodomains. The first plant TALE to be characterised was the Zea mays gene KNOTTED1 (KN1) in 1991. Upon its discovery, KN1 was noted to give rise to ectopic knots of tissue when expressed aberrantly in the leaf lamina. This work was a prelude to a rapidly expanding dataset which described TALE as regulators of developmental functions in plants, including morphogenesis. In an extension of this work, this thesis seeks to elucidate the function of uncharacterised TALE in Arabidopsis thaliana shoots.