Fig. 6

Proposed defense mechanisms of oil palm seedlings against hemibiotroph Ganoderma boninense during biotrophic and necrotrophic infection phases. Based on the NGS data on differentially expressed genes encoding TFs, two oil palm transcription factors (TFs), EgJUB1 and EgERF113 were discovered to regulate specifically under biotic stress during biotrophic and necrotrophic phases, respectively. The EgJUB1 TF binds to SNBE motif and directly regulates EgGAMYB and EgHSFs. The EgERF113 TF binds to GCC-box and DRE/CRT motifs which promotes PR and calcium responsive genes. The oil palm defense pathways are identified based on established defense mechanisms and new findings from this study. Black arrows represent direct regulation by encoded proteins/genes; blue arrows with broken lines suggest highly probable defense regulatory pathways; brown arrows indicate activation of downstream targets through binding to respective motifs. The question marks highlight the gaps in the oil palm defense mechanism that need to be further elucidated. Ca: calcium; CESA: cellulose synthase; CSLD: cellulose synthase-like D; DAMPs: damage-associated molecular patterns; DRE/CRT: dehydration response element/C-repeat; EIN3: ethylene insensitive 3; ET: ethylene; ETI: effector-triggered immunity; HR: hypersensitive response; HSFs: heat stress transcription factors; HSP: heat shock protein; JA: jasmonic acid; NPR1: NONEXPRESSOR OF PATHOGENESIS-RELATED GENE 1; PR: pathogenesis-related; PRRs: pattern recognition receptors; PTI: PAMP-triggered immunity; secondary wall NAC binding element (SNBE); SA: salicylic acid; TSS: transcription start site