| Ion channnels are a fundamental requirement of living cells. Aside from obvious functions in nutrient acquisition, ion channels play vital roles in environmental perception and signal transduction. Fluxes of ions, especially calcium ions, across cellular membranes are well documented responses of eukaryotes to virtually every conceivable environmental stimulus. The molecular and genetic basis for these calcium fluxes, however, is unknown in most cases. We screened candidate genes from the model plant Arabidopsis for osmosensitive calcium conductance activity in the heterologous system of Chinese Hamster Ovary (CHO) cells loaded with the calcium-responsive dye Fura-2. These screens led to the identification of the integral membrane protein Calcium-permeable Stress-responsive Cation channel1(AtCSCl) that conferred osmosensitive calcium conductance when heterologously expressed in CHO cells. AtCSCl doesn’t response to cold and heat. Bioinformatics analysis revealed that AtCSCl homologs which contained domain of unknown function (DUF)221presence in nearly all studied eukaryotes. Calcium imaging and electrophysiological experiments show that AtCSCl as well as two CSCs homologs from yeast and Human respectively are hyperosmotic-activated calcium-permeable channels. AtCSCl channel possess non-selective, non-rectify and time-independent electrophysiological properties. These results indicate that AtCSCl may play a role as a hyperosmotic sensor. And CSCs family proteins may function as conserved osmotic sensors across eukaryotes. What is more, we investigated the expression patterns of several AtCSCs genes and found that they expressed in different tissues with some overlaps. Moreover, several T-DNA insertion atcscs mutants were identified but unfortunately no obvious phenotype was observed in single atcscs mutants. |
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