Calcium is involved in the R^sub Mc1^^sub (blb)^-mediated hypersensitive response against Meloidogyne chitwoodi in potato

Functional characterization of the Columbia root-knot nematode resistance gene R ^sub Mc1 ( blb )^ in potato revealed the R gene-mediated resistance is dependent on a hypersensitive response and involves calcium. The resistance (R) gene R ^sub Mc1(blb)^ confers resistance against the plant-parasitic nematode, Meloidogyne chitwoodi. Avirulent and virulent nematodes were used to functionally characterize the R ^sub Mc1(blb)^-mediated resistance mechanism in potato (Solanum tuberosum). Histological observations indicated a hypersensitive response (HR) occurred during avirulent nematode infection. This was confirmed by quantifying reactive oxygen species activity in response to avirulent and virulent M. chitwoodi. To gain an insight into the signal transduction pathways mediating the R ^sub Mc1(blb)^-induced HR, chemical inhibitors were utilized. Inhibiting Ca^sup 2+^ channels caused a significant reduction in electrolyte leakage, an indicator of cell death. Labeling with a Ca^sup 2+^-sensitive dye revealed high Ca^sup 2+^ levels in the root cells surrounding avirulent nematodes. Furthermore, the calcium-dependent protein kinase (CDPK), StCDPK4 had a higher transcript level in R ^sub Mc1(blb)^ potato roots infected with avirulent nematodes in comparison to roots infected with virulent M. chitwoodi. The results of this study indicate Ca^sup 2+^ plays a role in the R ^sub Mc1(blb)^-mediated resistance against M. chitwoodi in potato.[PUBLICATION ABSTRACT]