Molecular cloning and characterization of putative virulence factors of Ganoderma boninense

Ganoderma boninense is a white rot fungus which causes basal stem rot (BSR) disease in oil palm. BSR is responsible for yield loss to the oil palm industry, which is the major economic growth driver of the country. To date, the existing solutions for the disease are not effective and the virulence factors responsible for the disease occurrence are understudied. The objectives of this study are to isolate the transcripts for putative virulence factors from G. boninense; to profile their gene expressions during fungal growth and plant-pathogen interactions; and to predict the transcription factor binding sites (TFBS) at the promoter sequence of selected putative virulence factors across different Ganoderma species. Four transcripts were selected from a previous study with the following criteria: i. present in the G. boninense-treated oil palm root transcriptomes (absent in control), ii. present in whole genome sequence of G. boninense, iii. encodes for secreted protein, and iv. has homologs involved in plant pathogenesis. This is the first report on the characterisation of metalloproteinase (U14090), aspartic protease (U42611), polysaccharide deacetylase (U128397), and lipase (U56931) as candidate virulence factors from G. boninense. The full- length cDNAs of the candidates were isolated from G. boninense BLSM5B, cloned, and verified by sequencing. Expression of these genes in mycelial cultures harvested at different time-points (7-, 14-, 21-, and 28-days after inoculation (dai) in potato dextrose broth), upon direct contact with host, and treatment with elicitors (i.e., salicylic acid, jasmonic acid, and hydrogen peroxide), were analysed by real-time PCR (qPCR). The gene expression of U56931 was up-regulated in mycelial cultures at 21- and 28-dai in comparison to that at 7-dai, whereas the expression of U42611 was down-regulated in mycelial cultures at 28-dai in comparison to that at 7-dai. Salicylic acid which is involved in plant biotic stress response was shown to be able to down-regulate the gene expression of U56931. The expression of these candidate genes was not responsive to elicitation of jasmonic acid, and hydrogen peroxide although jasmonic acid, and hydrogen peroxide also mediate plant defence signalling and respiratory burst oxidation, respectively. On the other hand, the gene expression of U14090 was up-regulated in G. boninense in contact with oil palm roots for 24- and 48-hours compared to the uninoculated control. In addition, common and unique TFBS in the promoter regions of candidate genes in selected Ganoderma species were predicted and compared. The findings provided an insight into the expression of putative virulence factors during plant-pathogen interactions. This information is important for gene-targeted study in the development of effective cure against G. boninense to minimize yield loss of the oil palm industry.

Text FBSB 2023 8 - Full Text.pdf Available under License Creative Commons Attribution Non-commercial No Derivatives. Download (7MB) Text FBSB 2023 8.pdf Restricted to Repository staff only Available under License Creative Commons Attribution Non-commercial No Derivatives. Download (8MB)

Actions (login required)

View Item