Identifying genes acting downstream of the RCO homeobox gene in leaf shape diversity.

The project will be supervised by Miltos Tsiantis at the Max Planck Institute for Plant Breeding Research.


Plant leaves are an attractive model to understand the genetic basis for evolutionary change because they show substantial morphological variation at different evolutionary scales. The Reduced Complexity (RCO) gene played a key role in leaf shape diversification in the crucifer family (Sicard et al., 2014; Vlad et al., 2014; Kierzkowski, Runions et al., 2019; Bhatia et al., 2023) to which the reference plant Arabidopsis thaliana belongs. RCO arose through gene duplication and encodes a class I homeobox-leucine zipper protein. Its function was discovered in Cardamine hirsuta, where it acts to divide the leaf into distinct leaflets by locally repressing growth at the leaf margin, creating a complex shape. This species-specific activity of RCO arose by neo-functionalization following gene duplication of its ancestral paralogue LMI1, which is conserved in seed plants. Specifically, RCO acquired a novel expression domain within the growth zone at the base of the leaf, where growth repression - a conserved function of the RCO/LMI protein – exerts a greater effect on leaf shape. RCO was secondarily lost in A. thaliana leading to leaf simplification, and its reintroduction in the A. thaliana genome is sufficient to increase leaf complexity (Vlad et al., 2014). One key question in the area is to identify the major effectors of RCO function, and this will be the focus of this project. We will identify genes responding to inducible expression of RCO in its native domain, which together with information from ChIP Seq of RCO and scRNA data, will help us to identify genes mediating RCO function

Key publication: Bhatia N, et al. (2023). Interspersed expression of CUP-SHAPED COTYLEDON2 and REDUCED COMPLEXITY shapes Cardamine hirsuta complex leaf form. Current Biology. doi:10.1016/j.cub.2023.06.037

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