DE NOVO TRANSCRIPTOME SEQUENCING AND IDENTIFICATION OF UPREGULATED GENES INVOLVED IN PHENYLPROPANOID PATHWAY OF Acacia mangium IN RESPONSE TO Ceratocystis INFECTION.

Vascular wilt disease, caused by Ceratocystis fungi is a major threat to Acacia mangium plantations in Southeast Asia. Previous studies reported that the activation of key enzymes in phenylpropanoid pathway indicates plant defense response towards pathogenic infection. Due to limited information on the defense mechanism of Acacia mangium against Ceratocystis, transcriptome sequencing was performed to study A. mangium's early defense mechanism upon infection. We sampled control (non-inoculated) and infected (inoculated) A. mangium at four-time points (1, 5, 10 and 15 days post-inoculation (dpi)). About 7,463 differentially expressed genes (DEGs) of which 164 unique transcripts with potential relevance to defense mechanism were identified based on Gene Ontology (GO). From Kyoto Encyclopaedia of Genes and Genomes (KEGG) analysis, ten key enzymes associated with phenylpropanoid pathway were upregulated after infection such as phenylalanine ammonia-lyase (PAL), peroxidase (POD), cinnamyl alcohol dehydrogenase (CAD), caffeoyl-CoA O-methyltransferase (CCoAOMT), cinnamoyl-CoA reductase (CCR), cinnamate 4-hydroxylase (C4H), phenylalanine/tyrosine ammonia-lyase (PTAL), caffeic acid O-methyltransferase (COMT), O-hydroxycinnamoyl transferase (HCT) and 4-Coumarate-CoA ligase (4CL). Eight of them were upregulated upon 15 dpi excluding HCT and 4CL. PAL, CAD, and POD transcripts were identified to express higher in infected samples compared to control, showing their important defensive role of A. mangium against Ceratocystis. [ABSTRACT FROM AUTHOR]