Identifying and characterizing the ubiquitinylation substrates of the central leaf growth and senescence regulator, BIG BROTHER

How plants grow from a small seed to their final stature appeals to the imagination of many

people. Plants are indispensable for our daily needs, therefore, it is crucial to understand the

mechanisms that drive plant growth and identify molecular links between genes that enhance final

leaf size and longevity. In this project, we will study the central growth regulator BIG BROTHER

(BB). BB limits leaf size and longevity and its inactivation leads to larger leaves that show a delayed

senescence. Recent transcriptome experiments have shown that the expression of many inhibitors

of growth and senescence regulators is triggered by BB. Most probably, BB modifies

transcriptional regulators of these genes, but these remain unknown. By combining transcriptomic

and proteomic approaches, we will identify these substrates of BB. Next, we will find out what

happens to those proteins after they are modified by BB (they can be degraded, for example). To

reveal their in leaf growth and senescence, we will quantify if mutants with an altered expression

show changes in leaf size or longevity. Finally, we will identify the interactors and downstream

targets of a subset of these proteins to complete the link between BB and the observed

downstream transcriptomic changes. This project will reveal new regulators of growth and

uncover new molecular links between known growth regulating genes. This way, our current view

on how leaves reach their final size will be significantly enhanced.