RESUMEN
In southeastern Brazil, the majority of the riparian ecosystems are fragmented and degraded mainly due to human activities. The perennial gymnosperm Podocarpus sellowii Klotzch is a typical tree species from a gallery forest in the rupestrian area. Ten alloenzymatic loci were used to estimate the allelic frequency of 232 individuals distributed in eight subpopulations naturally divided by rock outcrops. The results indicated high genetic variability for the species in all subpopulations, with HO varying from 0.593 to 0.658, and HE, from 0.484 to 0.502. No endogamy was observed within (f = -0.292) and for the population set (f = -0.264). Genetic divergence of the species between subpopulations was 2.1%. Historic gene flow was low between subpopulations located in different water streams, corroborating the positive and significant correlation between genetic and geographical distance (rm = 0.496, P = 0.022). Co-ancestry revealed that only population A presents continuous distribution of the genotypes up to 94 m. Sp statistics did not indicate significant spatial genetic structure in the populations. In all the subpopulations, values of effective sizes were higher than the numbers of sampled individuals. The balance between mutation and drift was not verified, indicating the occurrence of a recent population bottleneck. These data can be used to determine the most effective strategies for the genetic conservation of this species.
Asunto(s)
Cycadopsida/genética , Isoenzimas/genética , Brasil , Cycadopsida/enzimología , Ecosistema , Bosques , Flujo Génico , Frecuencia de los Genes , Flujo Genético , Variación Genética , Genotipo , Geografía , Repeticiones de Microsatélite , Árboles/genéticaRESUMEN
Protein kinases and phosphatases are responsible for several cellular events mediated by protein phosphorylation and dephosphorylation. Among these events are cell growth and differentiation and cellular metabolism. Casein kinase I (CKI) and casein kinase II (CKII) are involved in the phosphorylation of several substrates. Endogenous protein phosphorylation and casein kinase activity were investigated in the megagametophyte of the native Brazilian conifer Araucaria angustifolia, during seed development. It was observed that a number of different polypeptides are phosphorylated in vitro in the three megagametophyte stages of development tested (from globular, cotyledonary and mature embryos, respectively) and the phosphate was incorporated mainly in serine residues. The use of okadaic acid and vanadate in the phosphorylation reactions increased phosphate incorporation in several polypeptides suggesting the presence of serine/threonine as well as tyrosine phosphatases in the megagametophyte. Also, the results obtained in experiments with CKII inhibitor, GTP as phosphate donor, RNA hybridizations, and in-gel kinase assays indicate the presence of CKII in the A. angustifolia megagametophyte.