Understanding how auxin signalling mechanisms drive leaf morphogenesis – SERRATIONS

The understanding of molecular mechanisms involved in the control of organ or body size and shape represents one of the main challenges in developmental biology. Plants and more specifically plant leaves exhibit interesting features for such purpose as they can exhibit a wide variety of shapes according to the species, developmental phase and environmental factors. Leaves are perfect model systems to address this challenge. Moreover plant leaves also play an essential role in food production and as a source of renewable energy.
New leaves are formed de novo during plant growth and at each novel season for deciduous species, from small group of cells called meristems maintained through the activity of stem cells. Differences of leaf shape result mainly from differences in the pattern and level of dissection ranging from simple leaves to compound leaves, entire leaves to serrated, tooth-like margins or lobed leaves. Leaf margins contribute to a large extend to leaf growth and shape as all the outgrowths such as leaflets or serrations emanate from them and they also control the overall growth of the leaf.
Leaf growth and development result from the coordination in time and space of cellular divisions and cellular expansion, and expansion of certain plant cells reaches up to one thousand times their size when living the meristem. Transcription factors belonging to the CUP-SHAPED COTYLEDON (CUC) genes and homeodomain genes of the KNOTTED-LIKE (KNOXI) family were shown to be essential for the control of leaf size and shape. In addition, the phytohormone auxin is a critical regulator of growth and development, involved in the regulation and coordination of cell division and cell expansion. The mechanisms of auxin signalling are based on a complex set of co-receptors exhibiting high to low affinity for auxin and an even more complex modular network of transcriptional repressors and activators tightly controlling the expression of a large set of genes.
The SERRATIONS project is based on recent data relative to key transcription factors regulating leaf morphogenesis and advanced knowledge on the generic signalling mechanisms of the phytohormone auxin that plays a critical role in the control and coordination of cellular responses sustaining leaf size and shape. The goal of the project is to identify auxin signalling modules involved in leaf morphogenesis and to integrate these data in mathematical modelling to provide new insights into complex regulatory networks acting on leaf morphogenesis and to further test model-derived hypotheses.