Authors: FEN-YONG YAO, GUO-NING QI, JAMSHAID HUSSSAIN
Abstract: In recent years a slow-type anion channel (SLAC) family composing five members, including slow anion channel associated 1 (SLAC1) and four SLAC1 homologs (SLAHs), has been identified in Arabidopsis thaliana. The anion channels are activated by calcium-dependent protein kinases (CPKs) and play crucial roles in mediating anion fluxes across plasma membranes. SLAH2 is specifically expressed in root stele cells and has been characterized as a nitrate-selective anion channel activated by CPK21 and CBL-interacting protein kinase 23 (CIPK23). However, the interaction between CPKs and SLAH2 and how it is regulated remains to be elucidated. In this study we found that SLAH2 could be activated by a few CPKs from three subgroups of the CPK family. Out of those CPKs, the constitutively active form of CPK2 from subgroup 1 activates SLAH2, whereas the native as well as constitutively active form of CPK3 from subgroup 2 and CPK7, CPK10, and CPK32 from subgroup 3 activate SLAH2. We also explored the role of SLAH2 in root-to-shoot nitrate transport by measuring the nitrate contents in xylem sap, but no significant differences were observed between the slah2-1 T-DNA insertion mutant and SLAH2 overexpression lines. Together, these data demonstrate that SLAH2 is regulated by multiple CPKs with variable Ca2+ sensitivities. Further research is required to understand the role of SLAH2 in nitrate transport.
Keywords: Arabidopsis, anion channel, SLAH2, CPKs, nitrate, calcium
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