Poster: Plant Pathogen/Symbiont Interactions

Abs # 703: The hyphal wall components and glucan suppressor of hypersensitive cell death from an oomycete Phytophthora infestans stimulate RiCDPKs, the calcium dependent protein kinases, and the localization of the GFP reporter proteins in the signalling of potato cells

Presenter:	Furuichi, Naotaka , nfuru@agr.niigata-u.ac.jp
Authors	Furuichi, Naotaka  (A)   Okuta, Tomoo  (A)   Hassan, Amjad  (A)   Hatsugai, Noriyuki  (A)   Saitou, Kenta  (B)   Osawa, Michimasa  (A)   Yokokawa, Kazutoshi  (A)   Watahiki, Masaaki  (C)   Kinjou, Masataka  (B)
Affiliations:	(A): Niigata University (B): Hokkaido University (C): ICMB, The University of Edinburgh
Web Site:	http://www.niigata-u.ac.jp

In the presence of Caƒstart sup>2+ the kinase activity of the plasma membrane fraction of potato cells is stimulated by hyphal cell wall components (HWC) of the oomycete Phytophthora infestans. Ca2+-dependent protein kinases, CDPKs, show a large family of serine/threonine kinases in plants. We isolated two CDPK cDNAs (RiCDPK1 and RiCDPK2) from potato cv. Rishiri (R₁-gene). These CDPK transcripts are elevated after elicitor treatment. Recombinant kinases encoded by RiCDPK1 and RiCDPK2 were prepared to investigate the role of CDPKs in potato hypersensitive response (HR). We developed a new method for assaying kinase autophosphorylation by microtiter plates and found that autophosphorylation of RiCDPK1-his and RiCDPK2-his fusion proteins were stimulated by the P. infestans suppressor of HR. In the presence of Ca2+ and Mg2+, RiCDPK1 autophosphorylation was stimulated to a greater extent than RiCDPK2. We also found that smGFP-RiCDPK1 is localized to the potato plasma membrane. These data suggest that RiCDPK1 may play an important role in the HWC-induced signaling cascade in the plasma membrane leading to HR. We also suggest that RiCDPK1 and RiCDPK2 mediate signaling from the suppressors of HR, and that kinase-mediated signaling may result in the inhibition of HR during compatible interactions between potato cells and P. infestans.