Exploring the Interaction between Phytophthora palmivora and Oil Palm through Gene Co-expression Network Analysis Mariandrea García-Gaona1, David Botero-Rozo 1, Leonardo Araque1, Hernán Mauricio Romero 1,2 1Biology and Breeding Program, Colombian OiI Palm Research Center, Cenipalma. 2Biology Department, Universidad Nacional de Colombia Created with BioRender Poster Builder INTRODUCTION Phytophthora palmivora, the causal agent of Bud Rot (BR) in oil palm (Elaeis guineensis Jacq.), is responsible for significant crop losses in Colombia, affecting over 145,000 hectares in the last decade. Recent advancements have improved our understanding of P. palmivora's virulence mechanisms and host resistance. However, several unknown aspects remain, particularly concerning the oil palm host. In a transcriptomic study by Avila-Mendez et al. (2019), the interaction between P. palmivora and oil palm was investigated through a transcriptomic approach, with a focus on susceptible (Clon57) and resistant (Clon34) oil palm genotypes. Using RNAseq data from this study, we aimed to construct gene co-expression networks for both the pathogen and oil palm during compatible and incompatible interactions. Through this approach, we identified co- expressed gene hubs in P. palmivora that may play important roles during oil palm infection. Additionally, we observed signs of pathogen manipulation in susceptible oil palm materials, triggering an exaggerated response and compromising the phenylpropanoid pathway. In contrast, resistant oil palm materials demonstrated control over their response through putative Heat Shock Proteins (HSP), maintaining a balance between primary metabolism and biotic defense. Overall, this study provides insights into the molecular mechanisms underlying the interaction between oil palm and P. palmivora, which can contribute to the effective control of Bud Rot. METHODS RESULTS 1. P. palmivora gene networks exhibited distinct behaviors in response to Oil palm Clon34 and Clon57 P. palmivora-Clon34 grouped 251 differentially expressed genes of P. palmivora, and P. palmivora-Clon57 grouped 265 genes. The size of the nodes indicates their hub score, and the background colors correspond to modules or co-expressed groups. 3. Oil palm Clon34 and Clon57 exhibited different responses to P. palmivora GCN of Clon34 grouped 649 genes out of 1486 DEGs, with a correlation greater than 0.8 distributed in 27 modules, while GCN of Clon 57 grouped 1327 genes, distributed in 35 modules. 2. Biological Process GO terms enriched by P. palmivora in Clon57 Bar graph of P. palmivora . Graph shows the top 10 Biological process significantly enriched terms (p-value < 0.05) in interaction with oil palm. 4. Biological Process GO terms enriched by oil palm in response to P. palmivora. Bar graph of Oil Palm GO term enrichment analysis. Graph shows the top 20 Biological process significantly enriched terms (p-value < 0.05) in response to P. palmivora infection 5.Trends of gene expression for central genes during P. palmivora infection and oil palm defense Heatmap depicting gene expression patterns of central genes obtained form the GCNs.The color scale indicates relative expression levels, with red representing higher expression and blue representing lower expression. Row clustering was performed using correlation analysis. Row names correspond to gene annotations, and column names indicate the three time points (24, 72, and 120 hpi) for Clon34 and Clon57. CONCLUSIONS The co-expression networks of P. palmivora during successful infection in Clon57 showed that central or hubs were linked to genes associated with oxidative processes, NADH dehydrogenase, sulfur transporters, cytoplasmatic effectors, as well as elicitins and hydrolases. In the susceptible Clon57 genotype, there was enrichment and positive expression of genes related to abiotic stress, which can be attributed to the influence of P. palmivora during its infection process. The co-expression networks of th