Newer mechanism to control abscisic acid signalling in plants

Newer mechanism to control abscisic acid signaling in plants

Clade A protein phosphatase 2Cs (PP2Cs) are abscisic acid (ABA) co-receptors that block ABA signalling by inhibiting the downstream protein kinases.

ABA signalling is activated after PP2Cs are inhibited by ABA-bound  PYLs receptors in Arabidopsis. However, whether these PP2Cs are regulated by other factors remains unknown.

Authors in the journal Nature Communications report that ABI1 (ABA-INSENSITIVE 1) can interact with the U-box E3 ligases PUB12 and PUB13, but is ubiquitinated only when it interacts with ABA receptors in an in vitro assay.

A mutant form of ABI1-1 that is unable to interact with PYLs is more stable than the wild-type protein. Both ABI1 degradation and all tested ABA responses are reduced in pub12 pub13 mutants compared with the wild type.

Introducing the abi1-3 loss-of-function mutation into pub12 pub13 mutant recovers the ABA-insensitive phenotypes of the pub12 pub13 mutant.

Authors thus uncover an important regulatory mechanism for regulating ABI1 levels by PUB12 and PUB13.