Poster: Intracellular Signaling

Abs # 815: Possible Involvement of Calcium-Dependent Protein Kinase in the Benzoic Acid-induced Flowering of Lemna aequinoctialis strain 151

Presenter:	Beppu, Toshio , beppu@ntu.ac.jp
Authors	Beppu, Toshio  (A)   Sagare, Junicyhi  (A)   Kato, Noriyuki  (A)   Imazawa, Hideki  (A)   Tanaka, Osamu  (B)
Affiliations:	(A): Teikyo University of Science & Tech (B): Dep. Sci. Konann University

Lemna aequinoctialis strain 151,a weakly responsive short-day plant, flowers under continuous light in response to 10 ^-6 M benzoic acid (BA)added to the medium. We previouly reported that the movement of extracellular Ca ²⁺ into the cells through the calcium channel and the elevation of intracellular Ca ²⁺ concentration above a certain level are necessary for the BA-induced flowering. Here we report that a calcium-depedent protein kinase (CDPK) having 52kD-molecular weight is activated during the flower induction by BA. CDPK activity measured by an in-gel assay method was elevated to the maximum level by 6 to 12 h of treatment with BA in the presence of Ca ²⁺ but not in the absence of Ca ²⁺ . Both flowering response and CDPK activity were lowered by the inhibitors of CDPK (bisindolyl maleimide,chelerythrine chloride and D-erythro-sphingosine) but not by the inhibitors of calcium/calmodulin-dependent protein kinase (KN-62 and W7). These results indicate that activation of CDPK may be necessary for BA-induced flowering in Lemna . Now we are cloning a cDNA encoding CDPK.