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IN BRIEF

Two Protein Kinases Required for ABA Signaling in Arabidopsis

neckardt{at}aspb.org

Numerous studies have indicated that phosphorylation is an important component of ABA signaling. Fujii et al. (pages 485–494) identify two protein kinases in Arabidopsis, SNF1-RELATED PROTEIN KINASE2.2 (SnRK2.2) and SnRK2.3, that are required for the control of responses to ABA during seed germination, dormancy, and seedling growth. An snrk2.2 snrk2.3 double mutant (but not single mutants) exhibited strong ABA-insensitive phenotypes in seed germination and root growth inhibition as well as changes in seed dormancy. ABA-induced expression of several genes whose promoters contain an ABA response element (ABRE) was reduced in the double mutant, which also had a greatly reduced level of a 42-kD kinase activity capable of phosphorylating peptides from ABRE binding factors (ABFs). This suggests that SnRK2.2 and SnRK2.3 function redundantly in ABA signaling to activate ABRE-driven gene expression through the phosphorylation of ABFs.

Many elements of this story have been known or suspected for some time. This study is significant because it provides solid genetic evidence for the role of these two kinases in ABA signaling and introduces a well-defined genetic model for further investigation of the pathway (e.g., toward the identification of upstream components that activate the SnRKs and additional components that influence downstream gene expression).

View larger version (88K): [in this window] [in a new window] [as a PowerPoint slide]   The snrk2.2 snrk2.3 double mutant shows strong insensitivity to ABA-induced root growth inhibition.

www.plantcell.org/cgi/doi/10.1105/tpc.107.190211

Related articles in Plant Cell:

Identification of Two Protein Kinases Required for Abscisic Acid Regulation of Seed Germination, Root Growth, and Gene Expression in Arabidopsis

Hiroaki Fujii, Paul E. Verslues, and Jian-Kang Zhu
Plant Cell 2007 19: 485-494. [Abstract] [Full Text]  

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