Marie Curie Reintegration grant 2012-2016 (FP7-2011-CIG)
Title: Post-transcriptional networks regulating organ-specific and general infection mechanisms in the rice blast fungus
Project Leader: Ane Sesma
Host Institution: Centre for Plant Biotechnology and Genomics (CBGP) - UPM (Madrid, Spain)
The number of people suffering from chronic hunger has raised brusquely reaching one billion worldwide with the recent increase in food prices and the global economic crisis. It is expected a global population growth to more than 9 million people by 2050, and food production will have to increase between 40-60% in order to fulfil nutritional needs worldwide.
Blast disease caused by the ascomycetous fungus Magnaporthe oryzae is considered one of the most serious diseases of rice worldwide. M. oryzae can infect both leaf and root organs. M. oryzae-rice interaction is an excellent pathosystem for studying organ-specific pathogenic mechanisms used by fungi of the Magnaporthaceae family. This project aims to improve our understanding of M. oryzae infection process, which is an essential requirement for the development of effective and durable strategies against this devastating plant disease.
In Sesma lab, two pathogenicity-associated genes are being studied in more detail, the karyopherin Exp5 and Rbp35. The nucleocytoplasmic transporter M. oryzae Exp5 plays an essential role during root infection. Immunoprecipitation and deep sequencing experiments are being carried out to identify M. oryzae Exp5 interacting proteins and RNAs.
The M. oryzae Rbp35 protein is a component of the polyadenylation machinery involved in alternative polyadenylation. The rbp35 mutant is defective in leaf and root infection. To gain an insight into the mechanisms for polyadenylation and poly(A) site selection in M. oryzae, we have used a new genome-wide sequencing approach, termed “3’ T-fill” to carry out a comprehensive map of polyadenylation sites in M. oryzae. This genome-wide comparative analysis has helped us to identify i) the nucleotide context surrounding poly(A) sites in fungal pre-mRNAs; ii) the potential motif recognised by Rbp35; iii) Rbp35-dependent mRNAs, and iv) the dual function of the Rbp35 in the 3’ end processing of pre-mRNAs in M. oryzae. Currently, we are testing the involvement of alternative polyadenylation in M. oryzae pathogenicity by looking at two infection-related mRNAs. We are also initiating studies on the mechanisms that regulate transport and localization of transcripts relevant to fungal plant infection by following the in planta localisation of Rbp35 mRNA targets.
At present very little is known about the post-transcriptional mechanisms that regulate fungal plant infection. The functional characterisation of Exp5 and the genome-wide poly(A) mapping analysis are highlighting novel insights into the regulatory mechanisms that control M. oryzae plant infection. The mRNA localisation experiments will initiate innovative studies on local control of translation of M. oryzae proteins associated with pathogenicity.