Resumo

The genus Puccinia is considered to contain the most destructive genera of biotrophic fungi. P. psidii which causes the Eucalyptus rust (up to 60% losses in young plants). Despite of its economic importance, little is known about the biology of the fungus and its molecular interaction with their host. We sequenced P. psidii genomic DNA and obtained more 19,500 contigs annotated using the Blast2GO tools. Almost 50% of the sequences are associated with DNA metabolism, including retrotransposons which are highly represented within the fungal genome. The second most abundant GO term was associated with catabolism, includes a large proportion of glycoside hydrolases from different families, some of which are related to pathogenic processes (for instance GH3, GH5, GH16, GH18, GH61). In parallel, we evaluated the P. psidii transcriptomic analysis during the E. grandis infection. We designed a model system based on the selection of susceptible (S4) plants from a half-sib population using Brasuz1 and the pollen receptor. Previous microscopy studies were performed to define the important steps in the initial development of the disease process in susceptible plants (0-144hr). Using these data we designed an initial transcript sequencing experiments to cover the most important steps: 0 hours after infection (h.a.i), 6 h.a.i (germination), 12 h.a.i (penetration), 24 h.a.i (initiation of fungal colonization), 72 h.a.i (formation of haustorial mother cells and colonization) and 144 h.a.i (fungal sporulation). The fungal transcripts amount did not reached 5 % of total sequenced transcripts until 72 hour after infection (h.a.i). However, 144 h.a.i. P. psidii transcripts were 14% of the total. Among the deferentially expressed genes, we found transcripts related to catabolic process, growth and reproduction. To our knowledge it is the first report molecular analysis of the rust eucalyptus gene expression during the host infection. Although the sequence assembly is only a draft quality, it is a valuable resource for generating working hypothesis about the fungal biology and the interaction between eucalyptus-P. psidii, aiming for the development of strategies to control Eucalyptus rust in this crop.