TRANSCRIPT ACCUMULATION OF DEFENSE GENES IN TOMATO INFECTED BY THE FALSE ROOT-KNOT NEMATODE NACOBBUS ABERRANS
Nacobbus aberrans is a migratory-sedentary endoparasitic nematode that forms galls in the roots of infected plants. The purpose of this research was to correlate the expression of four defense-related genes to the N. aberrans life cycle in tomato roots. Transcript accumulation of pathogenesis-related protein PR-1, β-1,3-glucanase (PR-2), peroxidases (POX), and phenylalanine ammonia lyase (PAL) in tomato roots after inoculation with N. aberrans were estimated by qRT-PCR at 2, 7, 14, 21 and 28 days post-inoculation (dpi). The number of juveniles found in the radical system of tomato increased from 56 to 83 at 7 and 14 dpi, respectively, and to more than 95 juveniles at 21 dpi. Gene quantification revealed that the expression of pathogenesis-related genes varied during the evaluation time, confirming that syncytia formation and maintenance are very complex processes. At 2 dpi, gene expression changes were not statistically significant. At 7 dpi, PR-1 was the only up-regulated gene in infected plants compared to non-inoculated plants. At 14 dpi, the expression of PR-2, PAL and POX was increased in the inoculated plants, and at 21 dpi, the expression of PR-2 was decreased while PR-1 transcript accumulation exhibited a slight increase. Finally, at 28 dpi, the expression of PAL was increased, and the expression of POX was decreased. The gene expression alterations induced by N. aberrans could be necessary to ensure the successful completion of the nematode’s life cycle and to create suitable conditions for its establishment and development in tomato roots.