BackgroundThionins 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.ResultsCaThi 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.ConclusionThe results reported herein may ultimately contribute to future efforts aiming to employ this plant-derived AMP as a new therapeutic substance against yeasts.

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This work was carried out in collaboration between all authors. The authors AAFZ and RAS were responsible for running the experiment in the field, as well as performing the submission and doing the evaluators' chores. The authors SSB and APCGB were responsible for managing the entire experiment as well as statistical analyzes and writing the paper. The authors SP, FGT and MDC were responsible for the analysis of electron and optical microscopy as well as the interpretation of the results. All authors read and approved the final manuscript.

The seed coat develops primarily from maternal tissues and comprises multiple cell layers at maturity, providing a metabolically dynamic interface between the developing embryo and the environment during embryogenesis, dormancy and germination of seeds. Seed coat development involves dramatic cellular changes, and the aim of this research was to investigate the role of programmed cell death (PCD) events during the development of seed coats of cowpea [Vigna unguiculata (L.) Walp.]. We demonstrate that cells of the developing cowpea seed coats undergo a programme of autolytic cell death, detected as cellular morphological changes in nuclei, mitochondria, chloroplasts and vacuoles, DNA fragmentation and oligonucleosome accumulation in the cytoplasm, and loss of membrane viability. We show for the first time that classes 6 and 8 caspase-like enzymes are active during seed coat development, and that these activities may be compartmentalized by translocation between vacuoles and cytoplasm during PCD events.

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As espécies de Wunderlichia (Asteraceae) são endêmicas das regiões central e leste do Brasil, geralmente encontradas em afloramentos rochosos e sujeitas a altas irradiação solar e temperatura. Tais condições sugerem ocorrência de múltiplas adaptações xeromórficas em Wunderlichia azulensis. Este estudo visou caracterizar a morfoanatomia dos órgãos vegetativos de W. azulensis. Raízes, caules e folhas foram coletados de um afloramento rochoso no Maciço do Itaoca, Campos dos Goytacazes, RJ, Brasil. O material vegetal foi fixado, desidratado e emblocado em resina plástica para seções transversais. Testes histoquímicos foram realizados para identificação das classes químicas nas folhas e tricomas de W. azulensis. A morfologia dos tricomas foi avaliada em microscópio eletrônico de varredura. As raízes apresentaram uma estrutura morfoanatômica distinta que pode ser caracterizada como xilopódio. As folhas apresentaram um conjunto de atributos anatômicos adaptativos, como células epidérmicas com paredes anticlinais retas ou levemente sinuosas, alta densidade de tricomas e camada subepidérmica. Os testes histoquímicos revelaram substâncias fenólicas e óleos essenciais no mesofilo. Este estudo contribuiu para o conhecimento sobre as adaptações anatômicas das plantas rupícolas e de ambientes xeromórficos, e sugere futuros estudos para elucidação da estrutura das raízes e caules de W. azulensis.