The witches' broom disease is the main disease that affects cacao (Theobroma cacao), caused by the basidiomycete Moniliophthora perniciosa. Symptoms include stem swelling and excessive axillary shoots production on infected sites. Our research group has shown that the tomato (Solanum lycopersicum) miniature cultivar 'Micro-Tom' ('MT') is a suitable genetic model system to investigate the interaction with M. perniciosa, presenting typical symptoms of the disease. The development of witches' broom symtoms is related to plant hormonal signals, since the pathogen appears to cause a hormonal imbalance at the shoot apex of the host. The 'MT' model has a collection of mutant and transgenic lines with altered hormonal synthesis or perception, which represents an important resource for investigating the role of hormones in the pathogenesis. Furthermore, the physiological changes in cacao can be better investigated in the 'MT' system. Thus, in this proposal, 'MT' mutants and a transgenic line with changes on the perception or synthesis of auxin and cytokinin, will be inoculated with M. perniciosa and used for massive analysis of transcripts by RNA sequencing (RNA-seq) in a time course experiment. The results will be compared to available data from the transcriptome M. perniciosa x T. cacao interaction.
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