Deciphering the role of Calcium dependent protein kinases, CDPKs, in stress responses in potato plants

SCIORRA MARCELO; ULLOA RITA MARÍA; FANTINO ELISA; SEGRETIN MARÍA EUGENIA; GROSSI CECILIA EUGENIA MARÍA; SANTIN FRANCO

Norwich

Conferencia; Plant Calcium Signalling Conference; 2017

John Innes Centre

Calcium-dependent protein kinases (CDPKs) decode calcium (Ca2+) signals andactivate different signaling pathways involved in hormone signaling, plant growth,development, and both abiotic and biotic stress responses. Data mining of the potatogenome allowed us to identify twenty-six members of this family in Solanumtuberosum that can be classified into four groups (I to IV). Our group characterizedthree members of group II, StCDPK1/2/3, one member of group I, StCDPK7, and isnow analyzing two members of group III, StCDPK22/24 that harbor only three EFhandsin their calmodulin like domains. RT-qPCR analysis indicated thatStCDPK1/2/3 and 7 are ubiquitously expressed in the plant tissues with differentlevels of expression; however, potato plants harboring the reporter GUS gene underthe control of the CDPK promoters (proStCDPK1/2/3/7:GUS) show that each genedisplays a specific spatio-temporal expression profile. In particular, histochemicalanalysis indicated that StCDPK1 is strongly associated to the vascular system [1].StCDPK1/2/3 are predicted to be myristoylated and palmitoylated and both StCDPK1and 2 are associated to the plasma membrane [2]. Regarding StCDPK7, transientexpression assays show that this kinase displays a cytosolic/nuclear localization inspite of having a predicted chloroplast transit peptide [3]. StCDPK1/2/3 and 7 encodeactive protein kinases that are able to phosphorylate syntide-2 and Histone in a Ca2+-dependent way; however, each one displays preference for a specific substrate invitro. In the case of Group II isoforms, StCDPK1 was able to phosphorylate the auxintransporter StPIN4 [1], StCDPK2 strongly phosphorylates StABF transcription factor[4] and StCDPK3 phosphorylates StRSG and StABF [5]. On the other hand,StCDPK7 phosphorylates phenylalanine ammonia lyase isoforms, NtPAL1-4, and itsexpression was induced in systemic leaves upon Phytophthora infestans infection [2].CDPK promoters share many regulatory elements related to biotic and abioticstresses; but salt stress and dehydration-responsive elements are overrepresented inStCDPK2 promoter. With the aim of understanding the role of StCDPK2 and 7 indifferent stresses we are analyzing proStCDPK:GUS plants in response to high salttreatment and upon P. infestans infection. In addition, we obtained proS35:StCDPK2plants and exposed them to salt treatments. Preliminar experiments performed invitro indicate that proS35:StCDPK2 plants are more tolerant to salt than wild-typeplants, showing increased root growth, biomass and chlorophyll content, and lowerlevels of H2O2.