The gene regulatory logic of plant stem cell function
Plant shape is patterned by the activity of stem cells in the growing shoot tips and is a major determinant of plant productivity and yield. The size of the stem cell pool in Arabidopsis shoot tips is kept constant as plants grow by the activity of a small genetic circuit comprising small peptides, their receptors which act as kinases, and a downstream transcription factor. The CLV3 peptide acts via the CLV1 receptor to suppress the transcription of the WUSCHEL transcription factor, and WUSCHEL then moves to the CLV3 expression domain, promoting expression to generate a feedback loop to maintain the size of the stem cell pool. The hormonal environment of cells in the shoot apex is also important in regulating stem cell activity, and the CLV/WUS feedback loop intercepts auxin and cytokinin signalling.
The CLV/WUS pathway operates in a similar way in many flowering plants. However, the WOX gene family has undergone extensive duplications and losses in the plant tree of life, and CLV is only present in land plants. These findings raise questions about the fundamental requirements of land plant stem cell function.
This project aims to interrogate the fundamental requirements for land plant stem cell function by testing whether CLV acts via WOX genes in Physcomitrium. The project will involve generation of loss-and gain-of function mutants and reporter lines and phenotypic analysis to build a model of WOX function.
Combined with ongoing work in my lab on hormonal interactions with CLV, the findings will enable us to deduce the regulatory logic of Physcomitrium stem cell function. Comparison with findings from Arabidopsis will reveal generalities in the regulatory logic of land plant stem cell function, with broad potential significance in plant science.
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