Tyrosine phosphorylation of the GARU E3 ubiquitin ligase promotes gibberellin signalling by preventing GID1 degradation

Abstract

Gibberellin (GA) is a major hormone for plant growth and development. GA response is derived from the degradation of DELLA repressor proteins after GA-dependent complex formation of the GID1 GA receptor with DELLA. Genistein is a known tyrosine (Tyr) kinase inhibitor and inhibits DELLA degradation. However, the biological role of Tyr phosphorylation on the GA response remains unclear. Here, we demonstrate that GARU (GA receptor RING E3 ubiquitin ligase) mediates ubiquitin-dependent degradation of GID1, and that the TAGK2 plant Tyr-kinase is a target of genistein and inhibits GARU–GID1A interactions by phosphorylation of GARU at Tyr321. Genistein induces degradation of GID1 and accumulation of DELLA. Conversely, Arabidopsis garu mutant and TAGK2-overexpressing plants accelerate GID1 stabilization and DELLA degradation. Under salt stress, GARU suppresses seed germination. We propose that GA response is negatively regulated by GARU-dependent GID1 ubiquitination and positively by Tyr phosphorylation of GARU by TAGK2, and genistein inhibits GA signaling by TAGK2 inhibition.

Dehydration‐responsive nuclear proteome landscape of chickpea (Cicer arietinum L.) reveals phosphorylation‐mediated regulation of stress response

“…With respect to threonine as the central residue, there was a single overrepresented motif (Figure c). No conserved motif was found in case of tyrosine, which is in accordance with the previous reports (Nemoto et al, ). Proline directed pSP motif was found to be enriched among the dehydration‐induced dephosphorylated peptides.…”

Properties and functions of calcium‐dependent protein kinases and their relatives inArabidopsis thaliana

“…This phosphorylation reduced GARU–GID1 interaction, leading to stabilization of GID1. Despite the absence of a GA‐related phenotype in crk2 mutant potentially due to redundancy with other CRKs, these data suggest that AtCRK2 positively regulates GA signaling by stabilizing the GA receptor (Nemoto et al ., ). By contrast, crk1 displays a severe phenotype under continuous light (i.e.…”

“…Nonetheless, studies suggest that, like CDPKs, CRKs can display substrate specificity due to specific interaction (Li et al ., ; Liu et al ., ), but also share common substrates with variable efficiencies (Nemoto et al ., ). Interestingly, CRKs were reported to phosphorylate their substrates on tyrosine, supporting the dual‐specificity of those kinases (Table ; Nemoto et al ., , ). By contrast, this has not yet been observed for CDPKs, suggesting that phospho‐tyrosine may be restricted to autophosphorylation for CDPKs as a particular regulatory mechanism.…”

“…GA signaling is also mediated by AtCRK2, which controls the protein stability of the GA receptor gibberellin insensitive dwarf1 (GID1). Interestingly, GARU (GA receptor ring E3 ubiquitin ligase), responsible for proteasomemediated degradation of GID1, was phosphorylated in vitro and in vivo by AtCRK2 on Y321 (Nemoto et al, 2017). This phosphorylation reduced GARU-GID1 interaction, leading to stabilization of GID1.…”

Interplay between REVEILLE1 and RGA‐LIKE2 regulates seed dormancy and germination in Arabidopsis

“…Previous studies have demonstrated that DELLA protein stability is positively or negatively regulated by other factors. GA RECEPTOR RING E3 UBIQUITIN LIGASE promotes GAI accumulation by destabilizing the GID1A receptor (Achard et al, 2008;Nemoto et al, 2017), indicating that the stabilization of DELLAs is indirectly regulated by these factors. GA RECEPTOR RING E3 UBIQUITIN LIGASE promotes GAI accumulation by destabilizing the GID1A receptor (Achard et al, 2008;Nemoto et al, 2017), indicating that the stabilization of DELLAs is indirectly regulated by these factors.…”