An Arabidopsis SNF1-related protein kinase, AtSR1, interacts with a calcium-binding protein, AtCBL2, of which transcripts respond to light

AtSR1 is a protein kinase of Arabidopsis thaliana, which belongs to the SNF 1-related protein kinase subfamily 3. We previously showed accumulation of its transcripts to be responsive to light. In this study, we examined the i nteraction between AtSR1 and six calcineurin B like proteins of Arabidopsis and found that AtSR1 prominently interacts with one of them, AtCBL2, by ye ast two-hybrid assay. Interaction between AtSR1 and AtCBL2 could also be di rectly confirmed in vitro by pull down assay. RNA blot and reverse transcri ption-polymerase chain reaction analyses showed that transcripts of AtCBL2, and also of AtCBL1, another CBL, increased upon illumination of leaves. Th e physiological meaning of the interaction of AtSR1 and AtCBL2 is not clear , but they presumably function in signal transduction of light.