PLPKI: A novel serine proteinase inhibitor as a potential biochemical marker involved in horizontal resistance to Phytophthora infestans

MARIANA L. FELDMAN; ADRIANA B. ANDREU; SAMANTA KORGAN; MARÍA C. LOBATO; MARCELO HUARTE; LINDA L. WALLING; GUSTAVO R DALEO

PLANT BREEDING

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2014 vol. 133 p. 275 - 280

0179-9541

Potato leaves infected with P. infestans produced a serine proteinase inhibitor (PLPKI) with specificity for microbial proteinases. Sequencing of the first twenty residues at the NH2-terminus of the mature PLPKI polypeptide demonstrated that PLPKI is a novel member of the potato proteinase inhibitor I family. PLPKI inhibited the activity of extracellular proteinases produced by two pathogens of potato, P. infestans and R. solani, but was inactive against proteinases secreted into the culture media by the binucleate Rhizoctonia N2, a non-pathogenic fungus for potato. Western blot analysis showed a positive correlation between the levels of PLPKI and the degree of horizontal resistance, showing its highest accumulation in clone OKA 5632.11, which has been described as highly resistant. This correlation, together with the ability of PLPKI to completely abolish the secreted serine proteinase activity of P. infestans, suggests that PLPKI may have an active role in protecting potato plants from this pathogenic oomycete and that it could be used as a suitable biochemical marker to help breeders in the selection of cultivars with high degree of horizontal resistance.