Title : Characterization of transcription factors involved in early defense response during interaction of oil palm (Elaeis guineensis) with Ganoderma boninense.
Abstract:
Oil palm production generates large export earnings to many countries especially in Southeast Asian region. Manifestation of the disease caused by necrotrophic fungi, Ganoderma boninense on oil palm results in basal stem rot which compromises oil palm production leading to significant economic loss. Effective detection and disease control techniques are lacking while oil palm varieties that are resistant to the disease are not available to overcome the problem. Thus, understanding molecular defense mechanisms underlying early interactions of oil palm with G. boninense may be vital to promote preventive or control measure of the disease. In the present study, four months old of oil palm seedlings were infected via artificial inoculation using rubber wood blocks fully colonised with G. boninense. Roots of six biological replicates of treated and untreated oil palm seedlings were harvested at 0, 3, 7 and 11 days post inoculation (d.p.i). Next-generation sequencing (NGS) was performed to generate high-throughput RNA-seq data and identify differentially expressed genes (DEGs) during early oil palm-G. boninense interaction. Based on de novo transcriptome assembly, a total of 427,122,605 paired-end clean reads were assembled into 30,654 unigenes. Sixty-one transcription factors were categorized as DEGs according to stringent cut off-values of genes with log2 ratio [Number of treated oil palm seedlings/ Number of untreated oil palm seedlings] ≥ |2.0| (corresponding to 2-fold or more upregulation) with p-value ≤ 0.01. Transcription factors that respond specifically to G. boninense interaction were selected and separated from those that were also responsive to abiotic stress (empty rubber wood block control) by preliminary screening using reverse transcriptase polymerase chain reaction (RT-PCR). Transcription factors unique to early G. boninense interaction were further verified using quantitative real-time polymerase chain reaction (qRT-PCR). The promoter sequences of these genes were identified from the oil palm genome sequence and cloned into β-glucuronidase (GUS) reporter vector and used for functional characterisation using transient expression assay in G. boninense infected oil palm roots. This presentation will further elaborate on the promoter activity of the G. boninense induced oil palm genes and the different promoter motifs that may be involved in early defense response of oil palm against this devastating pathogenic fungi.
