MAP kinases MPK9 and MPK12 are preferentially expressed in guard cells and positively regulate ROS-mediated ABA signaling

Fabien Jammes, Charlotte Song, Dongjin Shin, Shintaro Munemasa, Kouji Takeda, Dan Gu, Daeshik Cho, Sangmee Lee, Roberta Giordo, Somrudee Sritubtim, Nathalie Leonhardt, Brian E. Ellis, Yoshiyuki Murata, June M. Kwak

Research output: Contribution to journalArticle

238 Citations (Scopus)

Abstract

Reactive oxygen species (ROS) mediate abscisic acid (ABA) signaling in guard cells. To dissect guard cell ABA-ROS signaling genetically, a cell type-specific functional genomics approach was used to identify 2 MAPK genes, MPK9 and MPK12, which are preferentially and highly expressed in guard cells. To provide genetic evidence for their function, Arabidopsis single and double TILLING mutants that carry deleterious point mutations in these genes were isolated. RNAi-based gene-silencing plant lines, in which both genes are silenced simultaneously, were generated also. Mutants 1carrying a mutation in only 1 of these genes did not show any altered phenotype, indicating functional redundancy in these genes. ABA-induced stomatal closure was strongly impaired in 2 independent RNAi lines in which both MPK9 and MPK12 transcripts were significantly silenced. Consistent with this result, mpk9-1/12-1 double mutants showed an enhanced transpirational water loss and ABA- and H2O 2-insensitive stomatal response. Furthermore, ABA and calcium failed to activate anion channels in guard cells of mpk9-1/12-1, indicating that these 2 MPKs act upstream of anion channels in guard cell ABA signaling. An MPK12-YFP fusion construct rescued the ABA-insensitive stomatal response phenotype of mpk9-1/12-1, demonstrating that the phenotype was caused by the mutations. The MPK12 protein is localized in the cytosol and the nucleus, and ABA and H 2O2 treatments enhance the protein kinase activity of MPK12. Together, these results provide genetic evidence that MPK9 and MPK12 function downstream of ROS to regulate guard cell ABA signaling positively.

Original languageEnglish
Pages (from-to)20520-20525
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume106
Issue number48
DOIs
Publication statusPublished - Dec 1 2009

Keywords

  • Abscisic acid
  • Anion channels
  • Protein kinase
  • Reactive oxygen species
  • Stomata

ASJC Scopus subject areas

  • General

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