The Dynamic Interaction between Oil Palm and Phytophthora palmivora in Bud Rot Disease: Insights from Transcriptomic Analysis and Network Modelling

Abstract

Bud Rot, caused by Phytophthora palmivora, is considered one of the main diseases affecting African oil palm (Elaeis guineensis). In this study, we investigated the in vitro molecular dynamics of the pathogen–host interaction by analyzing gene expression profiles from oil palm genotypes that were either susceptible or resistant to the disease. We observed distinct interactions of P. palmivora with resistant and susceptible oil palms through co-expression network analysis. When interacting with susceptible genotypes, P. palmivora exhibited upregulation of carbohydrate and sulfate transport genes. These genes demonstrated co-expression with apoplastic and cytoplasmic effectors, including cell wall degrading enzymes, elicitins, and RxLR motif effectors. The pathogen manipulated susceptible oil palm materials, exacerbating the response and compromising the phenylpropanoid pathway, ultimately leading to susceptibility. In contrast, resistant materials exhibited control over their response through putative Heat Shock Proteins (HSP) that maintained homeostasis between primary metabolism and biotic defense. Co-expressed genes related to flavonoids, WRKY transcripts, lectin-type receptors, and LRR receptors may play important roles in pathogen control. Overall, the study provides new knowledge of the molecular mechanisms underlying the interaction between E. guineensis and P. palmivora, which can contribute to controlling Bud Rot in oil palms and gives new insights into the interactions of P. palmivora with their hosts.

Infection of Phytophthora palmivora Isolates on Arabidopsis thaliana

“…Our result showed that genes related to the uptake of nutrients are co-expressed with candidate effectors and have similar pattern expressions as those previously reported when P. palmivora (CPPhZC_05) infected oil palm [22]. Specifically, we evaluated two genes that encode apoplastic effectors (Gh17 and CXE), which contained hydrolytic domains.…”

“…To study differences in isolates, we used a qRT-PCR approach to quantify ten previously detected P. palmivora genes involved in oil palm infection [22]. Hallmarks of the infection, Hmp1 and NmrA, were expressed during compatible infection.…”

“…These are involved in oil palm colonization of the isolate CPPhZC_05. Additionally, we evaluated five other genes that included the transcription factor NmrA (nitrogen metabolic regulation A), transmembrane proteins such as Hmp1 (Haustorium-specific membrane protein), SulP (Sulfate Permease), MFS_1 (major facilitator, sugar transporter), and FRE (ferric reductase), which are co-expressed with candidate effectors during oil palm infection [22]. Our results show statistical differences in the expression of each gene compared to the controls (Figure 7).…”

“…Ten genes of Phytophthora palmivora and ten of Arabidopsis thaliana were analyzed. Genes of P. palmivora were selected based on previous analyses that showed key genes for the pathogenesis process [22], and the Arabidopsis genes were selected as hallmarks for plant defense response [23]. Primers for qRT-PCR analyses were designed using Primer3 (v.0.4.0) and are listed in Table 1.…”