Two Calcium-Dependent Protein Kinases, CPK4 and CPK11, Regulate Abscisic Acid Signal Transduction inArabidopsis

Abstract

Many biochemical approaches show functions of calcium-dependent protein kinases (CDPKs) in abscisic acid (ABA) signal transduction, but molecular genetic evidence linking defined CDPK genes with ABA-regulated biological functions at the whole-plant level has been lacking. Here, we report that ABA stimulated two homologous CDPKs in Arabidopsis thaliana, CPK4 and CPK11. Loss-of-function mutations of CPK4 and CPK11 resulted in pleiotropic ABA-insensitive phenotypes in seed germination, seedling growth, and stomatal movement and led to salt insensitivity in seed germination and decreased tolerance of seedlings to salt stress. Double mutants of the two CDPK genes had stronger ABA-and salt-responsive phenotypes than the single mutants. CPK4-or CPK11-overexpressing plants generally showed inverse ABA-related phenotypes relative to those of the loss-of-function mutants. Expression levels of many ABA-responsive genes were altered in the loss-of-function mutants and overexpression lines. The CPK4 and CPK11 kinases both phosphorylated two ABA-responsive transcription factors, ABF1 and ABF4, in vitro, suggesting that the two kinases may regulate ABA signaling through these transcription factors. These data provide in planta genetic evidence for the involvement of CDPK/calcium in ABA signaling at the whole-plant level and show that CPK4 and CPK11 are two important positive regulators in CDPK/calcium-mediated ABA signaling pathways.

Modulation of Protein Phosphorylation, N-Glycosylation and Lys-Acetylation in Grape (Vitis vinifera) Mesocarp and Exocarp Owing to Lobesia botrana Infection

“…Calcium (Ca 2ϩ ) is an important secondary messenger involved in different defense (59,60). CDPKs are activated by pathogen elicitors and are important for disease resistance (61).…”

Ca2+-Dependent Protein Kinase11 and 24 Modulate the Activity of the Inward Rectifying K+ Channels inArabidopsisPollen Tubes

“…To further confirm this result in vivo, bimolecular fluorescence complementation (BiFC) assays were performed. CPK11 was localized to the cytoplasm and nucleus as described previously (Dammann et al, 2003;Rodriguez Milla et al, 2006;Zhu et al, 2007), and CPK24 was localized to the plasma membrane and nucleus ( Figure 4B). Our BiFC assays ( Figure 4C) showed not only that CPK11 and CPK24 interacted each other, but also that the CPK11/CPK24 complex was specifically localized to the plasma membrane of the cotransformed Arabidopsis mesophyll protoplasts.…”

Plant Stress Surveillance Monitored by ABA and Disease Signaling Interactions

“…Similarly CPK4 and CPK11 were shown to biochemically target ABF1 and ABF4 (Zhu et al, 2007). The lack of phosphorylation of ABF1 and ABF4, reduced ABAinduction of gene expression including ABI4, ABI5, RAB18, and KIN1, and more susceptible phenotypes to drought stress in cpk4-1 cpk11-2 (Zhu et al, 2007) well correlate with the proposed functions of CDPKs as an important positive regulator of ABA signal transduction. It is noteworthy to compare the above observation with recent results showing cpk4-2 cpk11-2 showed a defect in Ca 2+ oscillation-induced stomatal closures, whereas no effects on the ABA-induced stomatal closures .…”

“…Consistent to their roles in mediating ABA signaling in many different types of tissues, CPK32 was reported to interact directly with ABA responsive bZIP transcription factor4 (ABF4) and upregulate ABA-induced gene expression (Choi et al, 2005). Similarly CPK4 and CPK11 were shown to biochemically target ABF1 and ABF4 (Zhu et al, 2007). The lack of phosphorylation of ABF1 and ABF4, reduced ABAinduction of gene expression including ABI4, ABI5, RAB18, and KIN1, and more susceptible phenotypes to drought stress in cpk4-1 cpk11-2 (Zhu et al, 2007) well correlate with the proposed functions of CDPKs as an important positive regulator of ABA signal transduction.…”

“…It is also intriguing that ABA-activated OST1/SnRK2.6 can phosphorylate ABF3, which is then predicted to stabilize ABF3 (Sirichandra et al, 2010). However, the presence of multiple protein kinase bands nearby CPK4 in in-gel-kinase assays (Zhu et al, 2007) indicate that a protein kinase(s) other than CPK4 or SnRK2s could also be involved in parallel to consummate the fine-tuning of ABA and biotic signal transduction.…”