Nicotiana Tabacum Tolerance to CPSMV Involves Increased H2O2/phenol Contents and Adjustments of Defense Protein Biosynthesis and Expression of Initiation/elongation Factors

Abstract CPSMV is one of the various pathogens that infect cowpea (Vigna unguiculata L. Walp.), an important leguminous crop, and cause significant yield losses. To the best of our knowledge, there is no report on the reaction of tobacco, a model, non-leguminous plant, in response to CPSMV. In this study, we inoculated Nicotiana tabacum L. (var. Xanthi) leaves with a CPSMV isolate to evaluate which type of relationship (compatible, incompatible or tolerance) is established in this pathosystem and what are the plant biochemical responses to the CPSMV challenge. Tobacco plants were grown in vitro under controlled conditions and their leaves inoculated with CPSMV. The disease symptoms, the presence of the virus, and the tobacco biochemical responses were assessed in comparison with the mock-inoculated controls at 1, 2, and 6 days after inoculation (DAI). CPSMVCE modulated the activity of some enzymes and gene expression in tobacco to its own benefit, whereas, in parallel, N. tabacum actively responds against the viral infection. Accordingly, the severe disease symptoms caused by CPSMVCE in susceptible cowpea genotypes were not developed although the CPSMVCE viral particles were present in the tobacco leaves at 6 DAI. These findings suggest that N. tabacum (var. Xanthi) exhibited the patterns of a typical tolerant host to CPSMVCE. However, a comprehensive understanding of the mechanisms of tolerance of N. tabacum (var. Xanthi) to CPSMVCE is of utmost importance to develop new cowpea genotypes tolerant or resistant to this viral disease.