Morphological and transcript changes in the biosynthesis of lignin in oil palm (Elaeis guineensis) during Ganoderma boninense infections in vitro

Abstract

Lignification of the plant cell wall could serve as the first line of defense against pathogen attack, but the molecular mechanisms of virulence and disease between oil palm and Ganoderma boninense are poorly understood. This study presents the biochemical, histochemical, enzymology and gene expression evidences of enhanced lignin biosynthesis in young oil palm as a response to G. boninense (GBLS strain). Comparative studies with control (T1), wounded (T2) and infected (T3) oil palm plantlets showed significant accumulation of total lignin content and monolignol derivatives (syringaldehyde and vanillin). These derivatives were deposited on the epidermal cell wall of infected plants. Moreover, substantial differences were detected in the activities of enzyme and relative expressions of genes encoding phenylalanine ammonia lyase (EC 4.3.1.24), cinnamate 4-hydroxylase (EC 1.14.13.11), caffeic acid O-methyltransferase (EC 2.1.1.68) and cinnamyl alcohol dehydrogenase (CAD, EC 1.1.1.195). These enzymes are key intermediates dedicated to the biosynthesis of lignin monomers, the guaicyl (G), syringyl (S) and ρ-hydroxyphenyl (H) subunits. Results confirmed an early, biphasic and transient positive induction of all gene intermediates, except for CAD enzyme activities. These differences were visualized by anatomical and metabolic changes in the profile of lignin in the oil palm plantlets such as low G lignin, indicating a potential mechanism for enhanced susceptibility toward G. boninense infection.

Defense response changes in roots of oil palm (Elaeis guineensis Jacq.) seedlings after internal symptoms of Ganoderma boninense Pat. infection

“…The ability to inhibit mycelial growth of G. boninense and activate the oil palm early defense system in seedling nurseries is essential for resistance against G. boninense. Other findings have also suggested physical defense mechanisms through lignin deposition [31,33,34,61]. The activation of SA-associated defense mechanisms by SA has also been predicted in previous research [53,84].…”

“…Lignin content is important in the early defense against G. boninense infection [61]. At a later stage of infection, cell wall lignification was not sufficient in protecting the oil palm root from G. boninense infection [19,34].…”

“…At both four and seven months after planting, G. boninense infection reduced the average root PRX activity of oil palm. Peroxidase (PRX) is one of the enzymes involved in lignin biosynthetic processes [38,61]. Although it successfully inhibits fungal growth, the high PRX activity is not sufficient in preventing infection when G. boninense switches to the necrotrophic phase [61].…”

Transcriptomic analysis of resistant and susceptible banana corms in response to infection by Fusarium oxysporum f. sp. cubense tropical race 4

“…Interestingly, lignin metabolism and production (phenylpropanoid metabolism-related genes, such as PAL, POD and CCoAOMT) were also proved to be had important roles in response to multiple pathogens 43,46 . The activities of enzyme and relative expressions of genes encoding PAL, C4H and CCoAOMT which are key intermediates dedicated to the biosynthesis of lignin monomers were positively induced in oil palm plantlets infected by Ganoderma boninense , except for CAD 47 . The expression of HCT was up-regulated in upland cotton whereas PAL, 4CL, CAD, CCoAOMT and COMT were up-regulated in sea-island cotton.…”

Physcomitrium patens CAD1 has distinct roles in growth and resistance to biotic stress

“…AtCAD5 was only highly in roots [ 19 , 20 ]. To date, the effects of CAD on phenotypic traits of transgenic vascular plants have been extensively identified, and CAD engineering to modify lignin content or composition is widely used [ 21 , 22 ]. Nevertheless, little information is available about the roles of CAD in early terrestrial non-vascular plants.…”