A novel gibberellin response regulatory mechanism via tyrosine phosphorylation

October 23, 2017

Understanding the mechanism that prevents seed germination in highsalt conditions

A collaborative research group from Ehime University, Tokyo University of Science, NAIST, RIKEN CSRS and others isolated GARU, a protein that induces degradation of gibberellin receptors. Using a wheat cell-free protein synthesis system independently developed by Ehime University, the researchers discovered that GARU Tyr residues are phosphorylated by the TAGK2 protein. This TAGK2 Tyr phosphorylation prevents the interaction of GARU with gibberellin receptor proteins, blocking their degradation. However, the known Tyr kinase inhibitor genistein suppresses TAGK2 activity and reduces Tyr phosphorylation of GARU, which promotes receptor degradation. This is the gibberellin response regulatory mechanism by genistein. The collaborative group also found that GARU is responsible for inhibiting germination in a high-salt environment, as the shoot could not survive in such circumstances.

Gibberellins are a major agricultural chemical that needs precise control of application timing and amounts used. By manipulating the expression of GARU and TAGK2 genes found in this research and using genistein, it becomes possible to control gibberellin in terms of plant growth, the timing of flowering and seed germination, and control of various plant responses—for example, the creation of seedless grapes. Moreover, artificial manipulation of the GARU gene is expected to allow control of plant seed germination.

Original article
Nature Communications doi:10.1038/s41467-017-01005-5
K. Nemoto, A. Ramadan, G. Arimura, K. Imai, K. Tomii, K. Shinozaki, T. Sawasaki,
"Tyrosine phosphorylation of the GARU E3 ubiquitin ligase promotes gibberellin signalling by preventing GID1 degradation ".
Kazuo Shinozaki
Group Director
Gene Discovery Research Group