Perennial trees have a unique cambium stem cell division and differentiation that constantly renews the vascular system to thicken the stem, giving them the ability to grow indefinitely. By absorbing and fixing carbon dioxide and producing oxygen, tree growth produces sustainable and environmentally beneficial wood materials that humans use. A complex signaling system regulates the proliferation and differentiation of cambium stem cells, which are responsible for tree growth. It is yet unknown how these signals are perceived and transmitted by receptors.

 

Recently, Li Laigeng's group at the Chinese Academy of Sciences' Center for Excellence in Molecular Plant Science discovered the receptor-like protein kinase gene ASX, which plays an important role in signal transduction during the processes of tree wood formation and cell wall thickening. Although cambium cell division can continue after the gene is knocked out using gene editing technology, the process of dividing cells into xylem is halted, and the cells cannot complete normal cell wall thickening. ASX is found on the plasma membrane and forms a complex with the SERK2 and SERK4 proteins. ASX phosphorylation can be catalyzed by SERK2 and SERK4. According to the findings, ASX and SERK create a signaling module in tree stems that governs gene expression programs for xylem differentiation and cell wall thickening.

 

The discovery of the ASX-SERK signaling module not only gives us a new way to figure out and understand the signals that control the differentiation of tree cambium cells, but it also shows us how to control the thickening of wood cell walls and modify trees to make them have better wood qualities. 

 

This finding is published in the New Phytologist in an article titled "Screening genome-editing knockouts reveals the role of the receptor-like kinase ASX in the regulation of secondary xylem formation in Populus" (https://nph.onlinelibrary.wiley.com/doi/abs/10.1111/nph.18881). 

 

 

Prof. Laigeng Li, Group leader

National Key Laboratory of Plant Molecular Genetics, Center for Excellence in Molecular Plant Sciences (CEMPS), Chinese Academic of Sciences