Roles of RCN1, Regulatory A Subunit of Protein Phosphatase 2A, in Methyl Jasmonate Signaling and Signal Crosstalk between Methyl Jasmonate and Abscisic Acid

Abstract

Methyl jasmonate (MeJA) as well as abscisic acid (ABA) induces stomatal closure with their signal crosstalk. We investigated the function of a regulatory A subunit of protein phosphatase 2A, RCN1, in MeJA signaling. Both MeJA and ABA failed to induce stomatal closure in Arabidopsis rcn1 knockout mutants unlike in wild-type plants. Neither MeJA nor ABA induced reactive oxygen species (ROS) production and suppressed inward-rectifying potassium channel activities in rcn1 mutants but not in wild-type plants. These results suggest that RCN1 functions upstream of ROS production and downstream of the branch point of MeJA signaling and ABA signaling in Arabidopsis guard cells.

Nitric oxide functions in both methyl jasmonate signaling and abscisic acid signaling in Arabidopsis guard cells

“…These results are consistent with our previous results, i.e., NO is involved in both MeJA-and ABA-induced stomatal closure and functions downstream of the branching point of MeJA and ABA signaling in Arabidopsis guard cells. 7 Our finding implies that protein phosphatase 2A might positively regulate NO levels in guard cells (Fig. 2).…”

“…5 NO mediates elevation of cytosolic free Ca 2+ concentration ([Ca 2+ ] cyt ), inactivation of inward-rectifying K + channels and activation of S-type anion channels, 6 which are known to be key factors in MeJA-and ABA-induced stomatal closure. 2,[7][8][9] It has been reported that ROS was not induced by MeJA and ABA in the MeJA-and ABA-insensitive mutant, rcn1 in which the regulatory subunit A of protein phosphatase 2A, RCN1, is impaired. 7,10 We examined NO production induced by MeJA and ABA in rcn1 guard cells (Fig.…”

The Arabidopsis rcn1-1 Mutation Impairs Dephosphorylation of Phot2, Resulting in Enhanced Blue Light Responses

“…The rcn1-1 mutant was impaired in abscisic acid-induced stomatal closing and showed reduced abscisic acid-induced calcium increases. Whereas in wild-type seedlings both methyl jasmonate and abscisic acid induce stomatal closure, neither did the rcn1-1 mutant seedlings (Saito et al, 2008). The retardation of phot2 dephosphorylation in the rcn1-1 mutant described above could account for these results.…”

“…Both methyl jasmonate and abscisic acid normally induce a burst of reactive oxygen species and activate inward-rectifying potassium channels (Saito et al, 2008). However, the hormones fail to do either in the rcn1-1 mutant, suggesting that RCN1 functions upstream from reactive oxygen species production and membrane depolarization but downstream from the two growth regulators.…”

Inhibitory Effects of Methylglyoxal on Light-Induced Stomatal Opening and Inward K+Channel Activity inArabidopsis

“…8) For whole-cell current recordings, the pipette solution contained 30 mM KCl, 70 mM K-Glu, 2 mM MgCl 2 , 3.35 mM CaCl 2 , 6.7 mM EGTA, 10 mM HEPES adjusted to pH 7.1 with Tris, and the bath solution contained 30 mM KCl, 2 mM MgCl 2 , 40 mM CaCl 2 , and 10 mM MES titrated to pH 5.5 with Tris. 9) For data analysis, pCLAMP 8.2 software (Molecular Devices, Sunnyvale, CA) was used.…”