Age-associated growth control modifies leaf proximodistal symmetry and enabled leaf shape diversification
Xinmin Li, Hannah Jenke, Soeren Strauss, Yi Wang, Neha Bhatia, Daniel Kierzkowski, Rena Lymbouridou, Peter Huijser, Richard S. Smith, Adam Runions, Miltos Tsiantis
Abstract
However, the precise significance of SPL9 action for leaf symmetry and marginal patterning is unknown. By combining genetics, quantitative shape analyses, and time-lapse imaging, we show that PD symmetry of the leaf blade in A. thaliana decreases in response to an age-dependent SPL9 expression gradient, and that SPL9 action coordinately regulates the distribution and shape of marginal serrations and overall leaf form. Using comparative analyses, we demonstrate that heteroblastic growth reprogramming in Cardamine hirsuta, a complex-leafed relative of A. thaliana, also involves prolonging the duration of cell proliferation and delaying differentiation. We further provide evidence that SPL9 enables species-specific action of homeobox genes that promote leaf complexity. In conclusion, we identified an age-dependent layer of organ PD growth regulation that modulates leaf symmetry and has enabled leaf shape diversification.