| 20164209 |
Mosher S, Moeder W, Nishimura N, Jikumaru Y, Joo SH, Urquhart W, Klessig DF, Kim SK, Nambara E, Yoshioka K: The lesion mimic mutant cpr22 shows alterations in abscisic acid signaling and abscisic acid insensitivity in a salicylic acid-dependent manner. Plant Physiol. 2010 Feb 17.
A number of Arabidopsis thaliana lesion mimic mutants exhibits alterations in both abiotic stress responses as well as pathogen resistance. One of these mutants, cpr22, which has a mutation in two cyclic nucleotide-gated ion channels, is a typical lesion mimic mutant exhibiting elevated levels of salicylic acid (SA), spontaneous cell death, constitutive expression of defense-related genes, and enhanced resistance to various pathogens; the majority of its phenotypes are SA dependent (Yoshioka et al., 2001., Yoshioka et al., 2006). These defense responses in cpr22 are suppressed under high humidity conditions and enhanced by low humidity. After shifting plants from high to low humidity, the cpr22 mutant, but not wild type, showed a rapid increase in SA levels, followed by an increase in abscisic acid (ABA) levels. Concomitantly, genes for ABA metabolism were up-regulated in the mutant. The expression of a subset of ABA-inducible genes, such as RD29A and KIN1/2, were down-regulated, but others, like ABI1 and HAB1 were up-regulated in cpr22 after the humidity shift. cpr22 showed reduced responsiveness to ABA, not only in abiotic stress responses, but also in germination and stomatal closure. Double mutant analysis with nahG plants that degrade SA indicated that these alterations in ABA signaling were attributable to elevated SA levels. Furthermore, cpr22 displayed suppressed drought responses by long-term drought stress. Taken together these results suggest an effect of SA on ABA signaling/abiotic stress responses during the activation of defense responses in cpr22. |
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