From solving climate change to building space rockets, ERECTA - a multifaceted Receptor-Like Kinase.

Abstract

Wood and cork respectively originate from cell proliferation of the vascular cambium and the cork cambium. Both cambia consist of a single, bifacial, continuous ring of stem cells and share overlapping regulatory pathways. In Arabidopsis, the ERECTA (ER) receptor-like kinase is known to regulate several developmental processes including meristematic maintenance. Recent studies reported that mutation in the ER gene enhanced the vascular defects observed in the PHLOEM INTERCALADED WITH XYLEM (PXY) – also known as TDR – loss of function mutant. As PXY/TDR partially controls vascular cambium development, these results suggest that ER also regulates the activity of the vascular cambium. This raises the following questions: is ER also involved in cork cambium regulation? And what are the molecular mechanisms underpinning the ER-dependent cambium regulation? Using phylogenetic analyses and morphogenetic studies, we identified several EPIDERMAL PATTERNING FACTOR-LIKE (EPFL) peptides as potential ER ligands which may redundantly regulate cambium activity. Interestingly, we also found that EPFL4-6, initially thought to be main cambium regulators, did not appear with the evolution of vascular cambium. Furthermore, loss-of-function experiments suggest that the ER family (ERf) receptors not only genetically interact with the PXY family (PXf) receptors to regulate vascular cambium activity but also to control the initiation and maintenance of the cork cambium. These findings indicated that the ERf-PXf signalling network ubiquitously regulates the initiation and maintenance of stem cells in post-embryonic tissues. Additionally, expression studies showed that ERf and PXf receptors had overlapping expression patterns in both the vascular and cork cambium as well as their neighbouring tissues. Interestingly, these results suggest that ERf and PXf could physically interact. For this reason, we prepared transgenic lines and genetic constructs for future protein-protein interaction assays. Finally, we found that auxin signalling played a key role downstream of the ERf-PXf network to control stem cell activity post-embryonically.