Sequence analysis and gene expression of putative oil palm chitinase and chitinase-like proteins in response to colonization of Ganoderma boninense and Trichoderma harzianum

Abstract

Chitinases are glycosyl hydrolases that cleave the β-1,4-glycosidic linkages between N-acetylglucosamine residues in chitin which is a major component of fungal cell wall. Plant chitinases hydrolyze fungal chitin to chitin oligosaccharides that serve as elicitors of plant defense system against fungal pathogens. However, plants synthesize many chitinase isozymes and some of them are not pathogenesis-related. In this study, three full-length cDNA sequences encoding a putative chitinase (EgChit3-1) and two chitinase-like proteins (EgChit1-1 and EgChit5-1) have been cloned from oil palm (Elaeis guineensis) by polymerase chain reaction (PCR). The abundance of these transcripts in the roots and leaves of oil palm seedlings treated with Ganoderma boninense (a fungal pathogen) or Trichoderma harzianum (an avirulent symbiont), and a combination of both fungi at 3, 6 and 12 weeks post infection were profiled by real time quantitative reverse-transcription (qRT)-PCR. Our findings showed that the gene expression of EgChit3-1 increased significantly in the roots of oil palm seedlings treated with either G. boninense or T. harzianum and a combination of both; whereas the gene expression of EgChit1-1 in the treated roots of oil palm seedlings was not significantly higher compared to those of the untreated oil palm roots. The gene expression of EgChit5-1 was only higher in the roots of oil palm seedlings treated with T. harzianum compared to those of the untreated oil palm roots. In addition, the gene expression of EgChit1-1 and EgChit3-1 showed a significantly higher gene expression in the leaf samples of oil palm seedlings treated with either G. boninense or T. harzianum.

Defense gene expression in Sorghum bicolor against Macrophomina phaseolina in leaves and roots of susceptible and resistant cultivars

“…However, in our study, we obtained higher chitinase gene levels in leaf rather than in roots. Similar results were obtained by Yeoh et al (2012) in oil palm. Conversely, maximum expression level of chitinase and stilbene synthase was observed at 72 and 24 HPI, respectively.…”

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

“…Relative gene expression for lignin biosynthesis was performed in oil palm plantlets by calibrating the expression levels of respective genes in T2 and T3 plantlets with untreated controls (T1). According to Yeoh et al (), relative expression level of a gene that is higher than a twofold change or lower than a 0.5‐fold change as compared with the untreated control, is considered to be differentially expressed. From Fig.…”

“…Significant differences among the treatments at P < 0.05 were determined by Tukey multiple comparison tests. Differences in the lignin biosynthesis gene expressions in treated plantlets (T2 and T3) were compared with the untreated control (T1) according to Yeoh et al (), as classical standard parametric tests ( t ‐tests or anova ) which depended on assumptions may not be the suitable statistical analysis for gene expression quantification (Pfaffl ).…”

Evaluation of Malaysian oil palm progenies for susceptibility, resistance or tolerance to Fusarium oxysporum f. sp. elaeidis and defence‐related gene expression in roots

“…Likewise Yeoh et al . () reported increased gene expression of EgChit3‐1 in roots treated with either or both G. boninense or Trichoderma harzianum , whereas expression of EgChit1‐1 was not increased. The expression levels of chitinase (Class III) and β ‐1,3‐glucanase also increased in oil palm roots in response to Pseudomonas aeruginosa, inoculated as a potential endophyte (Sathyapriya et al ., ).…”

“…Up‐regulation of chitinase genes in roots was reported by Yeoh et al . () and in leaves by Naher et al . (), in both cases also in response to Trichoderma harzianum root inoculation.…”