Thionins are a family of plant antimicrobial peptides (AMPs), which participate in plant defense system against pathogens. Here we describe some aspects of the CaThi thionin-like action mechanism, previously isolated from Capsicum annuum fruits. Thionin-like peptide was submitted to antimicrobial activity assays against Candida species for IC50 determination and synergism with fluconazole evaluation. Viability and plasma membrane permeabilization assays, induction of intracellular ROS production analysis and CaThi localization in yeast cells were also investigated. CaThi had strong antimicrobial activity against six tested pathogenic Candida species, with IC50 ranging from 10 to 40 μg.mL−1. CaThi antimicrobial activity on Candida species was candidacidal. Moreover, CaThi caused plasma membrane permeabilization in all yeasts tested and induces oxidative stresses only in Candida tropicalis. CaThi was intracellularly localized in C. albicans and C. tropicalis, however localized in nuclei in C. tropicalis, suggesting a possible nuclear target. CaThi performed synergistically with fluconazole inhibiting all tested yeasts, reaching 100 % inhibition in C. parapsilosis. The inhibiting concentrations for the synergic pair ranged from 1.3 to 4.0 times below CaThi IC50 and from zero to 2.0 times below fluconazole IC50. The results reported herein may ultimately contribute to future efforts aiming to employ this plant-derived AMP as a new therapeutic substance against yeasts.

Capsicum species are very important in Brazil because of economic, cultural and biological factors, and the country is considered to be a diversity center for this genus. Collection and maintenance of the genetic diversity in Capsicum are important to avoid genetic erosion. Besides the identification of species, the characterization and evaluation of accessions maintained in gene banks are of fundamental importance. For this purpose, multivariate methods have become an important tool in the classification of conserved genotypes. The objectives of this study were: i) to identify and characterize accessions of the Capsicum spp collection and draw conclusions about the potential use of certain accessions in different production sectors; ii) to estimate the genetic divergence among accessions using the Ward-MLM procedure, and iii) to evaluate the efficiency of the analysis of continuous and categorical data using the Ward-MLM procedure. Fifty-six Capsicum spp accessions were evaluated based on 25 descriptors, 14 of which were morphological and 11 agronomic. Based on the qualitative descriptors, it was possible to identify all species and, together with the agronomic descriptors, genotypes could be indicated with potential for use in various production sectors. Five was determined as the ideal number of groups by the criteria pseudo-F and pseudo-t2. The Ward-MLM procedure allowed the differentiation of the species C. annuum, C. frutescens, C. baccatum, and C. chinense in separate groups. The Ward-MLM procedure showed some level of efficiency in clustering Capsicum species analyzing morphological and agronomic data simultaneously.

Capsicum species are frequently described in terms of genetic divergence, considering morphological, agronomic, and molecular databases. However, descriptions of genetic differences based on anatomical characters are rare. We examined the anatomy and the micromorphology of vegetative and reproductive organs of several Capsicum species. Four Capsicum accessions representing the species C. annuum var. annuum, C. baccatum var. pendulum, C. chinense, and C. frutescens were cultivated in a greenhouse; leaves, fruits and seeds were sampled and their organ structure analyzed by light and scanning electronic microscopy. Molecular accession characterization was made using ISSR markers. Polymorphism was observed among tector trichomes and also in fruit color and shape. High variability among accessions was detected by ISSR markers. Despite the species studied present a wide morphological and molecular variability that was not reflected by anatomical features.