Salt stress in Arabidopsis: lipid transfer protein AZI1 and its control by mitogen-activated protein kinase MPK3.
A plant's capability to cope with environmental challenges largely relies on signal transmission through mitogen-activated protein kinase (MAPK) cascades. In Arabidopsis thaliana, MPK3 is particularly strongly associated with numerous abiotic and biotic stress responses. Identification of MPK3 substrates is a milestone towards improving stress resistance in plants. Here, we characterize AZI1, a lipid transfer protein (LTP)-related hybrid proline-rich protein (HyPRP), as a novel target of MPK3. AZI1 is phosphorylated by MPK3 in vitro. As documented by co-immunoprecipitation and bimolecular fluorescence complementation experiments, AZI1 interacts with MPK3 to form protein complexes in planta. Furthermore, null mutants of azi1 are hypersensitive to salt stress, while AZI1-overexpressing lines are markedly more tolerant. AZI1 overexpression in the mpk3 genetic background partially alleviates the salt-hypersensitive phenotype of this mutant, but functional MPK3 appears to be required for the full extent of AZI1-conferred robustness. Notably, this robustness does not come at the expense of normal development. Immunoblot and RT-PCR data point to a role of MPK3 as positive regulator of AZI1 abundance.
Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Sciences, Muthgasse 18, 1190 Vienna, Austria.
Andrea
A
Pitzschke
Sneha
S
Datta
Helene
H
Persak
D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects / Q000235:genetics; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D012965:Sodium Chloride / Q000494:pharmacology
C539888:AZI1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D012965:Sodium Chloride; C458516:AtMPK3 protein, Arabidopsis; D020929:Mitogen-Activated Protein Kinase Kinases
AZI1; Arabidopsis; MAPK; MPK3; in vivo interaction.; lipid transfer protein; phosphorylation; salt stress