Physiological, epigenetic, and proteomic responses in Pfaffia glomerata growth in vitro under salt stress and 5-azacytidine.

Plants adjust their complex molecular, biochemical, and metabolic processes to overcome salt stress. Here, we investigated the proteomic and epigenetic alterations involved in the morphophysiological responses of Pfaffia glomerata, a medicinal plant, to salt stress and the demethylating agent 5-azacytidine (5-azaC). Moreover, we investigated how these changes affected the biosynthesis of 20-hydroxyecdysone (20-E), a pharmacologically important specialized metabolite. Plants were cultivated in vitro for 40 days in Murashige and Skoog medium supplemented with NaCl (50 mM), 5-azaC (25 µM), and NaCl + 5-azaC. Compared with the control (medium only), the treatments reduced growth, photosynthetic rates, and photosynthetic pigment content, with increase in sucrose, total amino acids, and proline contents, but a reduction in starch and protein. Comparative proteomic analysis revealed 282 common differentially accumulated proteins involved in 87 metabolic pathways, most of them related to amino acid and carbohydrate metabolism, and specialized metabolism. 5-azaC and NaCl + 5-azaC lowered global DNA methylation levels and 20-E content, suggesting that 20-E biosynthesis may be regulated by epigenetic mechanisms. Moreover, downregulation of a key protein in jasmonate biosynthesis indicates the fundamental role of this hormone in the 20-E biosynthesis. Taken together, our results highlight possible regulatory proteins and epigenetic changes related to salt stress tolerance and 20-E biosynthesis in P. glomerata, paving the way for future studies of the mechanisms involved in this regulation.

Ecogeografia de populações de erva-baleeira (Varronia curassavica) no Norte e Vale do Jequitinhonha em Minas Gerais / Ecogeography populations of Cordia (Varronia curassavica) in North and Jequitinhonha Valley in Minas Gerais, Brazil

O objetivo deste estudo foi avaliar as condições ecogeográficas e edafoclimáticas dos ambientes de ocorrência da erva-baleeira (Varronia curassavica) nas mesorregiões Norte e Vale do Jequitinhonha de Minas Gerais. O estudo foi efetuado em 15 sítios de ocorrência dessa espécie, localizados em 14 municípios sob o bioma Cerrado e ocorreu nos tipos de vegetação Cerrado, Caatinga, restinga e floresta. Os sítios estão localizados predominantemente entre 495 e 895m de altitude, e as plantas localizam-se sempre na parte inferior da topossequência. A precipitação média anual variou de <1.000mm a 1.500mm e a temperatura média anual variou de <19 a 24°C. A espécie tolera solos fortemente ácidos e com alta saturação de alumínio, ocorrendo em diferentes níveis de fertilidade e classes de solo. Nas mesorregiões Norte e Vale Jequitinhonha de Minas Gerais, a erva-baleeira não apresentou condições ecogeográficas e edafoclimáticas específicas para a sua ocorrência.

The objective of this study was to evaluate the ecogeographic and edaphoclimatic conditions of the environments of occurrence of Cordia (Varronia curassavica) at the mesoregions Northern and Jequitinhonha Valley in Minas Gerais. The study was conducted in 15 places of occurrence of this species, located in 14 municipalities under the Cerrado biome and occurred in the Cerrado, Caatinga, marsh and, forest vegetation types. The places are located predominantly between 495 and 895m of altitude, and the plants are located always at the bottom of the top sequence. The annual average rainfall ranged from <1,000mm to 1,500mm and the annual average temperature ranged from <19 to 24°C. The species tolerates acid soils with high aluminum saturation, occurring at different fertility levels and soil types. In the mesoregions Northern and Jequitinhonha Valley in Minas Gerais the Cordia showed no ecogeographic and climatic specific conditions for its occurrence.