PROTEINASE INHIBITOR TYPE-2: CHARACTERIZATION AND EFFECT ON SOUTHERN ROOT-KNOT NEMATODE RESISTANCE IN TOBACCO (Nicotiana tabacum L.)

Proteinase inhibitors (PIs) are polypeptides that occur naturally in a wide range of plants and are considered to be an essential part of the plant's natural defense system. The aims of this study were to characterization of PI2 and determine of its effect on nematode (Meloidogyne incognita) resistance in Nicotiana tabacum. Resistant (KY9) and susceptible (Ergo) genotypes were inoculated by M. incognita race 2 and total RNA were extracted from roots. qPCR was performed by exclusive primers for PI2 (Q40561) and EF1 alpha (reference gene) and determined PI2 fold changes in two, three and four days after inoculation. Results showed significant difference of PI2 expression in resistant and susceptible genotypes and three time courses. Bioinformatics analysis revealed PI2 is an unstable protein and has three proteinase inhibitory domains with a trance membrane region. Proteinase inhibitory domains are trypsin and chymotrypsin inhibitor. Two conserved residues are in PI2 protein, which seems to be very important. Phylogenetic relationship of inhibitor precursor-repeats in Nicotiana sp. revealed seven groups.