EXPRESSION ANALYSIS OF GENES ASSOCIATED WITH DEFENSE IN THE MODEL OIL PALM -Thielaviopsis paradoxa

Spear rot disease in oil palm, is caused by a pathogenic fungus Thielaviopsis paradoxa. The OxG hybrid provides a valuable genetic resource for selecting resistant germplasm and stablish resisntance-associated gene to this pathogen. In this study, the 517-coded OxG hybrid was identified as a resistant genotype that limited the colonization of T. paradoxa, while another 485-coded OxG hybrid showed high susceptibility. To understand the hybrid transcriptional response to T. paradoxa infection, these two OxG hybrid materials were inoculated with this pathogen and its transcriptional profile was compared by RNA sequencing at six time points (0, 24, 48, 72, 96 and 120 hpi). To establish the time points, a characterization of the development of the disease was performed and a severity scale was established. 1798 differentially expressed genes (DEG), including 454 up-regulated genes and 86 downregulated genes, were detected in hybrid 517, compared to hybrid 485. The transcription profiles of twenty putative genes related to oil palm defense were measured by reverse transcription and quantitative PCR at the stipe of oil palm hybrids. Genes are involved in the processes of perception and transduction signals, generation and purification of ROS, a pathway related to phenylpropanoid, serine protease inhibitors, transcription factors, phytohormone biosynthesis (AJ and ET) and proteins related to pathogenesis. These results show an increase in the expression of these genes within the first 24 hpi in hybrid 517 and that this overexpression was maintained over evaluated time. This overexpression in the early stages of infection could contribute to mediate resistance to T. paradoxa. In conclusion, the results provided information on the dynamic defense process of the OxG hybrid and suggested that the oil palm hybrid materials respond differently in terms of expression of the phenylpropanoid pathway and pathogenesis-related proteins to confer defense and resistance to this disease.