Upstream kinases of plant SnRKs are involved in salt stress tolerance

Summary Sucrose non‐fermenting 1‐related protein kinases (SnRKs) are important for plant growth and stress responses. This family has three clades: SnRK1, SnRK2 and SnRK3. Although plant SnRKs are thought to be activated by upstream kinases, the overall mechanism remains obscure. Geminivirus Rep‐Int...

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Bibliographic Details
Published in:The Plant journal : for cell and molecular biology 2018-01, Vol.93 (1), p.107-118
Main Authors: Barajas‐Lopez, Juan de Dios, Moreno, Jose Ramon, Gamez‐Arjona, Francisco M., Pardo, Jose M., Punkkinen, Matleena, Zhu, Jian‐Kang, Quintero, Francisco J., Fujii, Hiroaki
Format: Article
Language:English
Subjects:
Alleles
Arabidopsis
Arabidopsis - enzymology
Arabidopsis - genetics
Arabidopsis - physiology
Arabidopsis Proteins - genetics
Arabidopsis Proteins - metabolism
Arabidopsis thaliana
Gene Expression Regulation, Plant
GRIKs
Growth conditions
Growth rate
Kinases
Original
Phosphorylation
Plant growth
Protein kinase
Protein Serine-Threonine Kinases - genetics
Protein Serine-Threonine Kinases - metabolism
Salinity
Salinity effects
Salinity tolerance
Salt Tolerance
Salts
Signal Transduction
Signaling
SnRKs
SOS2
Stress
Stresses
Substrates
Sucrose
Sugar
upstream kinases
Yeast
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Summary:Summary Sucrose non‐fermenting 1‐related protein kinases (SnRKs) are important for plant growth and stress responses. This family has three clades: SnRK1, SnRK2 and SnRK3. Although plant SnRKs are thought to be activated by upstream kinases, the overall mechanism remains obscure. Geminivirus Rep‐Interacting Kinase (GRIK)1 and GRIK2 phosphorylate SnRK1s, which are involved in sugar/energy sensing, and the grik1‐1 grik2‐1 double mutant shows growth retardation under regular growth conditions. In this study, we established another Arabidopsis mutant line harbouring a different allele of gene GRIK1 (grik1‐2 grik2‐1) that grows similarly to the wild‐type, enabling us to evaluate the function of GRIKs under stress conditions. In the grik1‐2 grik2‐1 double mutant, phosphorylation of SnRK1.1 was reduced, but not eliminated, suggesting that the grik1‐2 mutation is a weak allele. In addition to high sensitivity to glucose, the grik1‐2 grik2‐1 mutant was sensitive to high salt, indicating that GRIKs are also involved in salinity signalling pathways. Salt Overly Sensitive (SOS)2, a member of the SnRK3 subfamily, is a critical mediator of the response to salinity. GRIK1 phosphorylated SOS2 in vitro, resulting in elevated kinase activity of SOS2. The salt tolerance of sos2 was restored to normal levels by wild‐type SOS2, but not by a mutated form of SOS2 lacking the T168 residue phosphorylated by GRIK1. Activation of SOS2 by GRIK1 was also demonstrated in a reconstituted system in yeast. Our results indicate that GRIKs phosphorylate and activate SnRK1 and other members of the SnRK3 family, and that they play important roles in multiple signalling pathways in vivo. Significance Statement Since plants face diverse, often coincidental stresses throughout their lifetime, they have to integrate multiple signals to organize growth, development and stress responses. This work shows that GRIKs, which are essential players in sugar signalling pathway as upstream kinases of SnRK1s, also work in salt tolerance of Arabidopsis and identified SOS2, a SnRK3, as a potential substrate of GRIKs in the salinity signalling pathway.
ISSN:0960-7412
1365-313X
DOI:10.1111/tpj.13761