RESUMO
The effect of Radopholus similis, Pratylenchus araucensis, Meloidogyne spp., and their interaction was evaluated in seedlings of Musa AAB 'Dominico Hartón'. The study was conducted in a nursery in Palestina, Caldas department, Colombia. Forty-day-old plantain seedlings were infected separately with 750, 1,500, 2,250 and 3,000 of each species of nematodes/plant. Two experiments were conducted to evaluate the damage of R. similis, P. araucensis, Meloidogyne spp. and the mixture of 750 R. similis + 750 P. araucensis + 750 Meloidogyne spp. compared with the mixture of different proportions (1,500, 2,250 and 3,000 of each species of nematodes). Noninfected plants were included as a control treatment, for a total of 17 treatments in a randomized complete block design with ten replications. Twelve weeks after inoculation, all nematodes, both alone and in combination, reduced (p < 0.05) plantain dry root and shoot weight. In two experiments, R. similis, P. araucensis, and Meloidogyne spp. alone, each with a population density of 3,000, reduced (p < 0.05) root dry weight by 32.5%, 9.5% and 49%, respectively, and decreased (p < 0.05) shoot dry weight by 21.5%, 23%, and 31.5%, respectively, compared to the control. The interaction of nematodes with the lowest population decreased root (33%) and shoot (21%) weight. We conclude that the growth of 'Dominico Hartón' seedlings was affected by plant-parasitic nematodes, but the greatest damage occurred with concomitant nematode infection.
RESUMO
Plant pathogenic organisms secrete proteins called effectors that recognize, infect and promote disease within host cells. Bacteria, like Pseudomona syringae, use effectors with DnaJ function to disrupt plant defenses. DnaJ proteins (also called Hsp40) are a group of co-chaperone molecules, which assist in the folding of proteins. Despite the described role of DnaJs as effectors in several groups of pathogens, this group of proteins has never been correlated with the infection process in plant parasitic nematodes. In this study, we analyze the importance of DnaJ for plant parasitic nematodes. To do that, we compare the number of DnaJ proteins in nematodes with different lifestyles. Then, we predict the secreted DnaJ proteins in order to detect effector candidates. We found that Meloidogyne species have more secreted DnaJs than the rest of the nematodes analyzed in the study. Particularly, M. arenaria possess the highest proportion of secreted DnaJ sequences in comparison to total DnaJ proteins. Furthermore, we found in this species at least five sequences with a putative nuclear localization signal, three of them with a serine rich region with an unknown function. Then, we chose one of these sequences (MG599854) to perform an expression analysis. We found that MG599854 is over-expressed from 3 days post inoculation onwards in tomato plants. Moreover, MG599854 seems to be enough to produce cell death in Nicotiana benthamiana under transient expression conditions. In concordance with our results, we propose that DnaJ proteins are a potential source of effector proteins in plant parasitic nematodes.