Protein extract from Cereus jamacaru (DC.) inhibits Colletotrichum gloeosporioides growth by stimulating ROS generation and promoting severe cell membrane damage.

Mandacaru (Cereus jamacaru DC.), is a cactaceous symbol of caatinga vegetation at Brazilian Northeast region, however, there are no much studies about biochemical properties of this species. Here, the pioneering study brings very relevant data to highlight the importance of research with endemic plants of the caatinga. Afterward, the presence of enzymes such as peroxidase, protease, chitinase, ß-1,3-glucanase, and serine (trypsin) and cysteine (papain) protease inhibitors were evaluated. The peroxidase activity was higher in roots than other tissues. The ß-1,3-glucanase and proteolytic activity were prominent in stem and roots. The chitinase activity and protease inhibitor for both classes analyzed were detected in the stem and fruit peel. Antifungal activity against Colletotrichum gloeosporioides showed the root extract has a promising inhibitory activity on this economical important phytopathogenic fungus. After the contact of the hyphae with root extract increase in membrane permeability, based on Propidium Iodide (PI) uptake, and production of reactive oxygen species (ROS) were detected, compared to negative control. In addition, Scanning Electron Microscopy (SEM) analysis showed morphological damage on hyphae structure indicating that the treatment debilitates either cell membrane or cell wall leading to the cell death C. gloeosporioides.

Enhanced Synthesis of Antioxidant Enzymes, Defense Proteins and Leghemoglobin in Rhizobium-Free Cowpea Roots after Challenging with Meloydogine incognita.

The root knot nematodes (RKN), Meloydogine spp., particularly Meloidogyne incognita and Meloidogyne javanica species, parasitize several plant species and are responsible for large annual yield losses all over the world. Only a few available chemical nematicides are still authorized for RKN control owing to environmental and health reasons. Thus, plant resistance is currently considered the method of choice for controlling RKN, and research performed on the molecular interactions between plants and nematodes to identify genes of interest is of paramount importance. The present work aimed to identify the differential accumulation of root proteins of a resistant cowpea genotype (CE-31) inoculated with M. incognita (Race 3) in comparison with mock-inoculated control, using 2D electrophoresis assay, mass spectrometry identification and gene expression analyses by RT-PCR. The results showed that at least 22 proteins were differentially represented in response to RKN challenge of cowpea roots mainly within 4-6 days after inoculation. Amongst the up-represented proteins were SOD, APX, PR-1, ß-1,3-glucanase, chitinases, cysteine protease, secondary metabolism enzymes, key enzymes involved in ethylene biosynthesis, proteins involved in MAPK pathway signaling and, surprisingly, leghemoglobin in non-rhizobium-bacterized cowpea. These findings show that an important rearrangement in the resistant cowpea root proteome occurred following challenge with M. incognita.

A ConA-like lectin from Dioclea guianensis Benth. has antifungal activity against Colletotrichum gloeosporioides, unlike its homologues, ConM and ConA.

This study reports on the antifungal activity of Dgui, a ConA-like lectin from Dioclea guianensis seeds. Dgui inhibited conidial germination but not mycelial growth of Colletotrichum gloeosporioides. The lectins ConA and ConM from Canavalia ensiformis and Canavalia maritima, respectively, share high levels of amino acid sequence similarity (>84%) with Dgui and have the same specificity toward glucose/mannose but had no effect on the fungus. Fluorescence microscopy showed that both Dgui and ConM bind to C. gloeosporioides ungerminated conidia. However, Dgui did not bind to C. gloeosporioides germinated conidia and germ tubes and was not inhibitory to mycelial growth. Because only Dgui inhibited germination of the fungus, C. gloeosporioides conidia might have surface-specific germination targets recognized by Dgui but not by its homologues, ConM and ConA. Therefore, Dgui is a candidate for biotechnological approaches for improving the resistance of various nutritionally and commercially important crops that are affected by C. gloeosporioides.