Development of biotechnological strategies involving CDPKS and PGPB to generate potato plants tolerant to salinity and Phytophthora infestans

F SANTIN; E FANTINO; CEM GROSSI; RM ULLOA

CABA

Congreso; Reunión Conjunta de Sociedades de Biociencias; 2017

SAIB/SAB/SAIC

Salinity of soils affects plant development and is responsible for great losses in crop yields. Potato plants can grow well in soils with an electrical conductivity (EC) of 1,7 dS/m, however tuber yield decreases more than 50% at 5.9 dS/m. Calcium is a universal second messenger that responds to biotic and abiotic stimuli. Calcium dependent protein kinases (CDPKs) sense the fluctuation in cytosolic Ca2+ levels and participate in stress responses. Particularly, StCDPK2 promoter contains elements responsive to ABA, dehydration and desiccation. Transgenic plants 35S::StCDPK2 lines B and E presented higher biomass and greater root development under 50 mM NaCl. In order to compare the expression profile of CDPK2 in both normal and saline conditions we analyzed two transgenic lines (St2B and St2K) harboring reporter gene beta-glucuronidase (GUS) under the control of CDPK2 promoter. These plants were grown in solid MS media (2% agar) and were then treated with 150 mM NaCl for 1, 4 and 12 hours. Histochemical and fluorometrical GUS activity was conducted in leaves and roots. GUS activity was higher on the cells of the root cap under saline stress. Fluorometrical analysis correlated with this observation in line St2B. On the other hand, line 35S:CDPK2 A that exhibited a stronger tolerance to saline stress presented bacterial colonies associated to the root. The microorganism was isolated and 16S rDNA partial sequencing identified it as belonging to Methylobacterium sp. Treatment with 50 mM NaCl produced a reduction in chlorophyll content and root development which was mitigated with Methylobacterium inoculation. Moreover, a preliminary study showed its capacity to antagonize the phytopathogenic oomycete Phytophthora infestans the causal agent of late blight. Taken together, our results suggest that potato StCDPK2 could mediate the response to salt stress and that this plant growth promoting bacteria (PGPB) could play a significant role in saline tolerance and biocontrol.