How a molecular switch shapes the growth of plant organs

Researchers from the John Innes Center and partners from the Chinese Academy of Sciences have discovered a molecular switch that determines differential cell growth and organ shape.

The growth regulator auxin promotes cell growth through a surface protein called transmembrane kinase 1 (TMK1). At st cell surface TMK1 modulates cell wall properties that promote cell growth. But TMK1 also signals the opposite effect of growth retardation cell nucleuswhere it suppresses cell growth by reducing auxin-mediated gene expression.

Dr. Bengo Gu and colleagues have shown how TMK1 performs these seemingly opposing functions in different parts of the cell. This involves cleaving the TMK1 protein on the cell surface and transporting some of the cleaved protein into the nucleus. Although this process is fairly common, identifying the proteins that cleave the protein has been difficult due to technical challenges.

The proteins involved are members of the DA1 peptidase family. These enzymes break down many proteins involved in growth reactions and help shape the growth of organs. Demonstration of TMK1 cleavage of the DA1 family reveals how they modulate the flow of information from the cell surface to the nucleus to shape cell size and organ growth. Determining these processes makes an important contribution to our understanding of plant growth.

Dr. Gu, a research fellow at the John Innes Center, says their “work demonstrated that DA1 family peptidases act on the hormone signal transmission, indicating a general mechanism of signal transduction from the plasma membrane to the nucleus. The findings potentially offer a way to improve crop seed germination.”

“Modulation of receptor-like transmembrane kinase 1 nuclear localization by DA1 peptidases in Arabidopsis” was published in Proceedings of the National Academy of Sciences.