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Transcriptome comparison of resistant and suscentible Hevea brasiliensis cultivars infected by Microcyclus ulei

Garcia D., Carels N., Araujo de Souza L., Koop D.M., Pujade-Renaud V., Da Silva D.C., Mattos C.R.R., Cascardo J.C.M.. 2009. In : 3rd IRRDB Workshop on the Hevea Genome and Transcriptome, 3-5 June, 2009, Montpellier, France. s.l. : s.n., p. 30-48. IRRDB Workshop on the Hevea Genome and Transcriptome. 3, 2009-06-03/2009-06-05, Montpellier (France).

- Background and Aims South American Leaf Blight (SALB) is caused by an ascomycota, Microcyclus ulei (P. Henn.) v. Arx., and is the most damaging disease in Latin America and the most important threat for rubber tree plantations in Asia and Africa which produce 95% of the world rubber with susceptible genotypes. Because few information are available to understand the biological process of the disease development, suppression subtractive hybridization (SSH) approach was developed in order to identify genes differentially expressed at different stages of the pathogenic interaction with Microcyclus ulei, with a particular interest for defence and stress-related genes. - Methods To identify candidate genes and gain better understanding of the hostpathogen interaction in the pathosystem Hevea brasiliensis - Microcyclus ulei, Suppression Subtractive Hybridization libraries were compared. Leaflets of the MDF 180 partially resistant cultivar and the PB314 susceptible cultivar were inoculated with M. ulei. Using 6 to 72 h.p.i, 4 to 28 d.p.i, and 34 to 58 d.p.i infected and healthy leaflets, five cDNA libraries, highly enriched for M. ulei - induced genes were prepared. - Key Results Within 8027 clones randomly picked and sequenced from the libraries, 1165 singlets and 458 contigs for a total of 1623 non-redundant sequences were obtained. The redundancy of each SSH libraries were variable, ranging from 87% in PB314 4-28 d.p.i libary to 23% in MDF180 4-28 d.p.i library. Sequence analysis allowed the assignment of a putative functional category for 38% of sequences, whereas 15% of sequences corresponded to unknown function and 47% did not show any significant similarity with other proteins present in the databank. Clustering of the whole sequence reveal a high degree of dissimilarity between the genes isolated in each library. Moreover, the obtained ESTs compared with the Hevea latex transcriptome, appear highly specific of the leaf tissue. The comparison of the five libraries displayed a drastic diminution of the number of over-expressed genes in PB314 genotype during the infection process, differently from MDF180 genotype for which the number of genes related to stress and defence display an increase of 56%. These preliminary results are put together with symptomatic and histological observations.

Mots-clés : hevea brasiliensis; microcyclus ulei; bahia

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