Histomolecular responses in susceptible and resistant phenotypes of Capsicum annuum L. infected with Phytophthora capsici

In recent years, there has been a significant spread of Phytophthora infections in several countries, causing problems in the horticultural sector. In this article, cytological, histological and protein differences between resistant plants (Criollos de Morelos 334) and susceptible plants of Capsicum annuum L. infected with Phytophthora capsici were analyzed to evaluate morphological modifications and quantitative protein changes that could both be the target of infection and be involved in the response mechanism. On a morphological level, we carried out staining for cutin, cellulose, callose and to evaluate the oxidative stress of Capsicum annuum samples. Morphological information suggests that Phytophthora capsici causes severe damage to susceptible plants, but not to resistant plants, with damage limited mainly to the pith and the phloem. Differences in the deposition of callose between resistant, infected and non-infected plants were also observed, whereas this was not observed for susceptible, infected and non-infected plants. Since the deposition of callose was most intense in the xylem of infected resistant plants, this suggests that the accumulation of callose is a mechanism of resistance/defense against infection by Phytophthora capsici. One-dimensional protein analysis was performed using antibodies against TGase and actin. Uninfected susceptible plants and resistant plants (both infected and non-infected) have a very similar pattern of TGase accumulation but different from infected susceptible plants, indicating that the defensive mechanism of resistant plants might be based on the activation of specific TGase isoforms.