Functional identification of Ammopiptanthus mongolicus anion channel AmSLAC1 involved in drought induced stomata closure

Drought, one of the most acute abiotic stressors plants encountered, can adversely affect plants growth and development. The fast adjustment of stomatal aperture is necessary for effective drought tolerance in plants. Anion channels were identified as important controllers of stomatal closing via mediating anion efflux. The present study reports the isolation and identification of a SLAC (SLOW ANION CHANNEL-ASSOCIATED 1) or-tholog from an ancient desert shrub Ammopiptanthus mongolicus (Maxim.) Cheng f. (AmSLAC1), which is functionally conserved for ABA and drought induced stomata closure. AmSLACI was primarily expressed in shoots, especially in guard cells. The transcription of AmSLAC1 was induced in response to ABA and PEG treatments, implying the potential involvement in ABA-induced drought stress responses. Fluorescence observation suggested that AmSLAC1 was localized in the plasma membrane. BiFC asssays demonstrated an interaction between AmSLAC1 and the typical calcium-dependent protein kinases AmCPK6. Ectopic expression of AmSLAC1 restores a slac1-defective phenotype in Arabidopsis. Furthermore, anion conductance mediated by AmSLAC1 can be activated by AmCPK6 in Xenopus oocytes. Taken together, these results demonstrate that the expression of AmSLAC1 enables the complement of the phenotypes of Arabidopsis slac1 mutants, indicating that AmSLAC1, as an anion channel and regulated by AmCPK6, is functionally conserved for ABA and drought induced stomata closure.