Abstract

Biosynthesis and Gene Expression of Lignin Intermediates in Oil Palm, Elaeis guineensis during Ganoderma spp. Fungal Infection

Christina Supramaniam, Assistant Professor, The University of Nottingham

Oil palm is an important economic crop and is a source of dietary energy for global populations. However, it has low disease resistance to basal stem rot (BSR) caused by Ganoderma spp. Plant cell wall lignifications could serve as the first line of defence, but the molecular mechanisms of this defence response in oil palm is poorly understood. This study investigates the biochemical, histochemical, enzymatic and gene expressions during the lignin biosynthesis events in young oil palm infected by Ganoderma boninense (GBLS strain). Lignothioglycolic acid (LTGA) assay, histochemical staining and microscopy, and gas chromatography (GC) experiments revealed significant accumulations of total lignin content and monolignol derivatives (syringaldehyde and vanillin), which were primarily deposited on the collenchyma and cuticle layers of cell wall of the infected oil palm. Comparative studies with control (T1) wounded (T2) and infected (T3) oil palm plantlets showed substantial differences in the enzyme activities and relative gene expressions of phenylalanine ammonia lyase (PAL), cinnamate 4-hydroxylase (C4H), caffeic acid O-methyltransferase (COMT) and cinnamyl alcohol dehydrogenase (CAD), the key intermediates dedicated to the biosynthesis of lignin monomers. Results confirmed an early biphasic transient induction of selected lignin biosynthesis genes and enzymes studied in oil palm (except for the induction of CAD enzyme) in response to the infection by GBLS. These differences accompanied by anatomical and metabolic changes in lignin profiles of the plantlets could enhance the tolerance of oil palm towards G. boninense infection.