Akter Rojina, Inoue Yasuhiro, Masumoto Saori, Mimata Yoshiharu, Matsuura Takakazu, Mori Izumi C, Nakamura Toshiyuki, Nakamura Yoshimasa, Murata Yoshiyuki, Munemasa Shintaro
Graduate School of Environmental and Life Science, Okayama University, Okayama, Japan.
Faculty of Agriculture, Okayama University, Okayama, Japan.
Physiol Plant. 2025 Jul-Aug;177(4):e70396. doi: 10.1111/ppl.70396.
In guard cells, cytosolic Ca acts as a second messenger that mediates abscisic acid (ABA)- and pathogen-associated molecular pattern (PAMP)-induced stomatal closure. It was reported that Arabidopsis cyclic nucleotide-gated ion channel 2 (CNGC2) functions as hydrogen peroxide (HO)- and PAMP-activated Ca-permeable channels at the plasma membrane of mesophyll cells and mediates Ca-dependent PAMP-triggered immunity. In this study, we examined the role of CNGC2 in the regulation of stomatal movement because CNGC2 is also expressed in guard cells. We found that stomata of the CNGC2 disruption mutant cngc2-3 are constitutively closed even in the absence of ABA or the flagellar-derived PAMP, flg22. Consistently, leaf temperatures of the cngc2-3 mutant were higher than those of wild-type (WT) plants. The stomatal phenotype of the cngc2-3 mutant was restored by complementation with wild-type CNGC2 under the control of the guard cell preferential promoter, pGC1. Elevation of cytosolic free Ca concentration in guard cells induced by flg22 and HO remained intact in the cngc2-3 mutant. The introduction of the ost1-3 mutation into the cngc2-3 background did not alter the stomatal phenotype. However, the stomatal phenotype of the cngc2-3 mutant was successfully rescued in the double disruption mutant cngc2-3aba2-2. Taken together, these results suggest that CNGC2 negatively regulates stomatal closure response and does not function as flg22- and HO-activated Ca channels in guard cells. Though CNGC2 is responsive for HO- and flg22-induced [Ca] elevation in mesophyll cells, the involvement of CNGC2 in the response to HO and flg22 in guard cells is questionable.
在保卫细胞中，胞质钙作为第二信使介导脱落酸（ABA）和病原体相关分子模式（PAMP）诱导的气孔关闭。据报道，拟南芥环核苷酸门控离子通道2（CNGC2）在叶肉细胞质膜上作为过氧化氢（H₂O₂）和PAMP激活的钙通透通道发挥作用，并介导钙依赖的PAMP触发免疫。在本研究中，我们研究了CNGC2在气孔运动调节中的作用，因为CNGC2也在保卫细胞中表达。我们发现CNGC2缺失突变体cngc2 - 3的气孔即使在没有ABA或鞭毛来源的PAMP（flg22）的情况下也组成型关闭。一致地，cngc2 - 3突变体的叶片温度高于野生型（WT）植物。在保卫细胞优先启动子pGC1的控制下，用野生型CNGC2互补可恢复cngc2 - 3突变体的气孔表型。flg22和H₂O₂诱导的保卫细胞胞质游离钙浓度升高在cngc2 - 3突变体中保持不变。将ost1 - 3突变引入cngc2 - 3背景中并没有改变气孔表型。然而，在双缺失突变体cngc2 - 3aba2 - 2中成功挽救了cngc2 - 3突变体的气孔表型。综上所述，这些结果表明CNGC2负向调节气孔关闭反应，并且在保卫细胞中不作为flg22和H₂O₂激活的钙通道发挥作用。尽管CNGC2对叶肉细胞中H₂O₂和flg22诱导的[Ca²⁺]升高有反应，但CNGC2是否参与保卫细胞对H₂O₂和flg22的反应仍值得怀疑。
