Composition, structure and phylogenetic implications of the cell wall in Pteridophyta

• Grant number: 05/02266-1
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: October 01, 2005
• End date: March 31, 2009
• Field of knowledge: Biological Sciences - Botany - Plant Taxonomy
• Principal Investigator: Marcos Silveira Buckeridge
• Grantee: Giovanna Bezerra da Silva
• Host Institution: Instituto de Botânica. São Paulo , SP, Brazil

Abstract

In previous studies, we focused on the composition of cell wall polysaccharides from 11 species of pteridophytes. They were chosen according to the most recent phylogenetic tree available, which is based on plant morphology and molecular markers. Our results suggest that there are two main groups of hemicelluloses in pteridophytes, one with xyloglucan and another with galactomannan as their principal hemiceluloses. These data did not corroborate the phylogeny currently accepted for pteridophytes and suggested that certain features of the cell wall seem to have evolved several times as observed, for example, for C4 and CAM metabolism in Bromeliaceae. In this project, we intend to extend our studies to a higher number of species (up to 100) aiming to understand the evolution of hemicelluloses in pteridophytes. In order to accelerate our analytical strategy, we preformed preliminary hemicellulose analyses of samples from fresh and herbarium samples of leaves of species previously studied by us (Blecknum polypodioides (stored in the Herbarium since 2004) and Adiantum raddianum (stored since 1968). We found the polysaccharide composition was not altered by herbarium storage. On the basis of these discoveries, the present proposal will focus in the analysis of a larger number of species of pteridophytes using hemicellulose analyses by direct enzymatic hydrolysis of leaf powders followed by analyses of oligosaccharides by mass spectrometry MALDI-TOF (technique well established by the group of Professor Markus Pauly at Marx Planck Institute, Golm and tested with success for Bechnum polypodioides by Marcos Buckeridge in that lab). Furthermore, 15 species will be subjected to complete cell wall fractionation and two of them will be submitted to linkage analyses using methylation followed by GC-MS. The results will be analyzed by multivariate analyses with the MALDI-TOF results aiming to probe the existence of groups of species with variable hemicellulose fine structures. With the data we expect to obtain in this work, it will be possible also to group species according to their hemicellulose compositions, in groups belonging to different biomes, habits etc. Thus, the greater number of species to be studied in this project will not only afford a better evaluation of the hypothesis raised in our previous work but will also help to understand important aspects of the adaptation mechanisms of Neotropical pteridophytes during evolution. Finally, from a sustainable use of biodiversity viewpoint, we expect that the knowledge produced will be a valuable to guide the search for novel pteridophyte polysaccharide materials for future applications in biotechnology. (AU)