Researchers at the John Innes Center and their partners at the Chinese Academy of Sciences have identified a molecular switch that determines the differential growth of cells and the shape of plant organs. Phys.org portal.
The growth regulator auxin promotes cell growth through a surface protein called transmembrane kinase 1 (TMK1). On the cell surface, this protein modulates cell wall properties that promote cell growth. But TMK1 also signals the opposite growth-slowing effect in the cell nucleus, where it suppresses cell growth by decreasing auxin-mediated gene expression.
Dr. Bengo Gu and colleagues showed how TMK1 performs these seemingly opposite functions in different parts of the cell. Cleavage of the TMK1 protein occurs on the cell surface, part of the cleaved protein is transferred to its nucleus. Although this process is quite common, the identification of the proteins involved in cleavage has previously been difficult.
The proteins involved are members of the DA1 peptidase family. These enzymes break down various proteins involved in growth reactions and promote the growth of plant organs.
The DA1 family TMK1 cleavage demonstration shows how they modulate the flow of information from the cell surface to the nucleus, shaping cell size and organ growth. Determination of these processes makes an important contribution to the understanding of plant growth processes.
This work proves that DA1 family peptidases affect hormonal signal transduction, which points to a common mechanism for signal transduction from the plasma membrane to the nucleus. The findings potentially offer a way to improve crop seed germination.