Proteomic and morphometric study of the in vitro interaction between Oncidium sphacelatum Lindl. (Orchidaceae) and Thanatephorus sp. RG26 (Ceratobasidiaceae).

Orchidaceae establish symbiotic relationships with fungi in the Rhizoctonia group, resulting in interactions beneficial to both organisms or in cell destruction in one of them (pathogenicity). Previous studies have focused mostly on terrestrial species with a few, preliminary studies, on epiphytes. To further our understanding of the molecular mechanisms involved in these symbioses, we evaluated the interaction between Oncidium sphacelatum Lindl. and the mycorrhizal fungus Thanatephorus sp. strain RG26 (isolated from a different orchid species) in vitro using morphometric and proteomic analyses. Evidence from the morphometric and microscopic analysis showed that the fungus promoted linear growth and differentiation of orchid protocorms during 98 days interaction. On day 63, protocorm development was evident, so we analyzed the physiological response of both organisms at that moment. Proteome results suggest that orchid development stimulated by the fungus apparently involves cell cycle proteins, purine recycling, ribosome biogenesis, energy metabolism, and secretion that were up-regulated in the orchid; whereas in the fungus, a high expression of proteins implicated in stress response, protein-protein interaction, and saccharides and protein biosynthesis were found in the symbiotic interaction. This is the first work reporting proteins differentially expressed in the epiphytic orchid-fungus interaction and will contribute to the search for molecular markers that will facilitate the study of this symbiosis in both wild orchids and those in danger of extinction.

DNA binding activity studies and computational approach of mutant SRY in patients with 46, XY complete pure gonadal dysgenesis.

Mutations of SRY are the cause of 46,XY complete pure gonadal dysgenesis (PGD) in 10-15% of patients. In this study, DNA was isolated and sequenced from blood leukocytes and from paraffin-embedded gonadal tissue in five patients with 46,XY complete PGD. DNA binding capability was analyzed by three different methods. The structure of the full length SRY and its mutant proteins was carried out using a protein molecular model. DNA analysis revealed two mutations and one synonymous polymorphism: in patient #4 a Y96C mutation, and a E156 polymorphism; in patient #5 a S143G mosaic mutation limited to gonadal tissue. We demonstrated, by all methods used, that both mutant proteins reduced SRY DNA binding activity. The three-dimensional structure of SRY suggested that besides the HMG box, the carboxy-terminal region of SRY interacts with DNA. In conclusion, we identified two SRY mutations and a polymorphism in two patients with 46,XY complete PGD, demonstrating the importance of the carboxy-terminal region of SRY in DNA binding activity.