A morphodynamic study of C. hirsuta leaf development

• Applicant: Professor Dr. Miltos Tsiantis
• Subject Area: Plant Cell and Developmental Biology
• Term: from 2017 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 318879394

Leaves are the main photosynthetic organs of seed plants and show considerable variation in their shape, making them a good model to understand development and diversity of biological forms. However, the morphogenetic basis for leaf shape diversity is poorly understood. We aim to address this question by comparing C. hirsuta which has complex leaves dissected to leaflets and A. thaliana which has simple leaves that bear only small serrations. Recently, we used genetics, advanced imaging and computational modelling to develop a growth-based framework explaining how genetic differences between these species are translated to differences in form. In this way, we established that a small gene regulatory network of the transcription factor CUP-SHAPE COTYLEDONS2 (CUC2), the auxin efflux transporter (PIN-FORMED1) PIN1 and auxin underlies the iterative pattern formation of leaf serrations as well as leaflets. In this context, the combination of local growth differences caused by species-specific action of two different homeobox genes accentuates growth differences created by this CUC2 patterning mechanism and underlies formation of leaflets instead of serrations. We also discovered that regulatory diversification of the CUC2 paralogue CUC1, that acts redundantly with CUC2, also contributes to these species-specific differences of leaf shape and promotes leaflet formation in C. hirsuta. On this basis, we propose to investigate how ChCUC1 is integrated in the above framework to influence leaf morphogenesis. Specifically, we will determine how ChCUC1 acts through selected downstream genes to influence cell growth, differentiation, cell proliferation and growth direction. To aid this investigation, we will use genetic mosaics to evaluate the degree of, and basis for, non-cell autonomy of its diverse functions. We will continue using computational approaches to synthesize the resulting information and guide experiments. The outcome of the project will be (i) information that clarifies the CUC1 cell-level mode of action and (ii) mechanistically grounded computational models that conceptualize the effect of CUC1 on leaf shape relative to previously described regulators.

• DFG Programme: Research Units
• Subproject of: FOR 2581: Quantitative Morphodynamics of Plants