Metagenomic Analysis to Assess the Impact of Plant Growth-Promoting Rhizobacteria on Peanut (Arachis hypogaea L.) Crop Production and Soil Enzymes and Microbial Diversity.

Peanut production could be increased through plant growth-promoting rhizobacteria (PGPR). In this regard, the present field research aimed at elucidating the impact of PGPR on peanut yield, soil enzyme activity, microbial diversity, and structure. Three PGPR strains (Bacillus velezensis, RI3; Bacillus velezensis, SC6; Pseudomonas psychrophila, P10) were evaluated, along with Bradyrhizobium japonicum (BJ), taken as a control. PGPR increased seed yield by 8%, improving the radiation use efficiency (4-14%). PGPR modified soil enzymes (fluorescein diacetate activity by 17% and dehydrogenase activity by 28%) and microbial abundance (12%). However, PGPR did not significantly alter microbial diversity; nonetheless, it modified the relative abundance of key phyla (Actinobacteria > Proteobacteria > Firmicutes) and genera (Bacillus > Arthrobacter > Pseudomonas). PGPRs modified the relative abundance of genes associated with N-fixation and nitrification while increasing genes related to N-assimilation and N-availability. PGPR improved agronomic traits without altering rhizosphere diversity.

Interspecific Variation between the American Quercus virginiana and Mediterranean Quercus Species in Terms of Seed Nutritional Composition, Phytochemical Content, and Antioxidant Activity.

This study aimed to evaluate a complete nutritional composition in the seeds Quercus virginiana to compare this nutritional composition with three Mediterranean Quercus species. We analyzed the seed morphometry, proximate composition, phytochemicals, and antioxidant capacity. The seed of Q. virginiana presented the smaller seed size and weight, while Q. suber presented the highest values. Moreover, Q. virginiana seeds showed the highest amounts of sugar and total lipids, digestibility, energy, palmitic acid, and stearic acid. On the other hand, Q. virginiana seeds showed the lowest values of linoleic acid. Moreover, Q. coccifera seeds presented the highest total phenolics and flavonoids contents and antioxidant activity. The clustering analysis revealed a significant similarity in seed morphometry and nutritional composition between the Mediterranean Q. ilex and Q. suber, grouping with the American Q. virginiana, but to a considerable distance; by contrast, the Mediterranean Q. coccifera was the most distant in the clustering analysis. The content of phenolics and flavonoids and digestibility value were the variables that contributed to the separation to a greater extent in the clustering of the four species. The nutritional and biological activity assessment of plant seed may be considered as an essential mission to find new sustainable sources and novel chemical agents. In this sense, Quercus seeds may be an alternative and a competitive food source for the agri-food industry.

Corrigendum: Proteomic Analysis and Functional Validation of a Brassica oleracea Endochitinase Involved in Resistance to Xanthomonas campestris.

[This corrects the article DOI: 10.3389/fpls.2019.00414.].

Proteomic Analysis and Functional Validation of a Brassica oleracea Endochitinase Involved in Resistance to Xanthomonas campestris.

Black rot is a severe disease caused by the bacterium Xanthomonas campestris pv. campestris (Xcc), which can lead to substantial losses in cruciferous vegetable production worldwide. Although the use of resistant cultivars is the main strategy to control this disease, there are limited sources of resistance. In this study, we used the LC-MS/MS technique to analyze young cabbage leaves and chloroplast-enriched samples at 24 h after infection by Xcc, using both susceptible (Veloce) and resistant (Astrus) cultivars. A comparison between susceptible Xcc-inoculated plants and the control condition, as well as between resistant Xcc-inoculated plants with the control was performed and more than 300 differentially abundant proteins were identified in each comparison. The chloroplast enriched samples contributed with the identification of 600 additional protein species in the resistant interaction and 900 in the susceptible one, which were not detected in total leaf sample. We further determined the expression levels for 30 genes encoding the identified differential proteins by qRT-PCR. CHI-B4 like gene, encoding an endochitinase showing a high increased abundance in resistant Xcc-inoculated leaves, was selected for functional validation by overexpression in Arabidopsis thaliana. Compared to the wild type (Col-0), transgenic plants were highly resistant to Xcc indicating that CHI-B4 like gene could be an interesting candidate to be used in genetic breeding programs aiming at black rot resistance.

Plant responses to tomato chlorotic mottle virus: Proteomic view of the resistance mechanisms to a bipartite begomovirus in tomato.

Tomato chlorotic mottle virus (ToCMoV) is a widespread bipartite Begomovirus species found in tomato fields in Brazil. In this study, plant responses and putative mechanisms associated with the 'Tyking'-derived recessive resistance to ToCMoV were investigated. Changes in the protein profile in the inoculated plants of two near isogenic tomato lines resistant ('LAM 157') and susceptible ('Santa Clara') to ToCMoV were analyzed. Seedlings were biolistically inoculated with an infectious ToCMoV clone. Leaves from infected plants (confirmed by PCR) were sampled at 15days after inoculation. Proteins were extracted using phenol and analyzed by shotgun MS (2D-nanoUPLC/HDMSE). Out of the 534 identified proteins, 82 presented statistically significant differences in abundance, including 35 unique proteins displayed in the resistant tomato inoculated with ToCMoV. Proteins associated to chromatin structure, cytoskeleton structure, cuticle biosynthesis, and ubiquitin pathway were identified and their putative roles during virus infection process were discussed. The protein profile analysis allowed for the development of a hypothetical model showing how the resistant host cell responds to ToCMoV infection. The data obtained provide a better understanding of resistant mechanisms used by the host plant to contain viral infection and could be the basis for further investigation in other plant-begomovirus pathosystems. BIOLOGICAL SIGNIFICANCE: In this study we propose a model of resistance to begomovirus in tomato and highlight host proteins, which could be targets for future investigations in plant-begomovirus pathosystems.

Metabolite and proteome changes during the ripening of Syrah and Cabernet Sauvignon grape varieties cultured in a nontraditional wine region in Brazil.

Grapevines are an important fruit crop from economic and cultural point of views in many countries, including Brazil, where the practice of vitiviniculture is being developed in different regions. We compared the anthocyanin concentration, the main organic acids and sugars, and the proteome profiles during berry ripening of Syrah and Cabernet Sauvignon grapes from two distinct geographical sources in São Paulo State. The proteome was mapped by two-dimensional gel electrophoresis and differentially abundant proteins during the ripening process were subjected to MALDI-TOF/TOF-MS analysis. An increase in sugar concentration and in anthocyanin content was observed, as well a decrease in the tartaric and malic acid concentration. A total of 128 spots varied with geographical origin, grape variety, and ripening stage, with 108 being identified. The identified proteins resulted in 80 gene products. A multivariate analysis of protein abundance clustered the samples according to grape variety, geographical origin, and stage of ripening, and showed the possibility of using proteomics to characterize three variables: variety, area where grown, and the ripening process. The changes observed during the ripening process corresponded to enzymes involved in sugar and organic acid metabolism. These results are in accordance with the metabolic profile reported for the process. BIOLOGICAL SIGNIFICANCE: Given the importance of discriminating grapes, thus making the adulteration of wines more difficult, in this paper we showed the possibility of differentiating varieties of grapes, geographical area of cultivation and stage of ripening by combining the results of differentially abundant protein determinations and multivariate analysis.