Expression of selected pathogenesis-related proteins at early stage of Ganoderma boninense infection in Elaeis guineensis jacq. seedlings
Basal stem rot (BSR) is the most devastating oil palm disease caused by Ganoderma boninense. It is only evident when the infection has progressed by 60–70% which is too late to cure the palm. Studies on early defense responses are required to provide insightful information on the...
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| Format: | Thesis |
| Language: | English |
| Published: |
2019
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/90774/1/IPTSM%202020%203%20-%20IR.pdf |
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| Summary: | Basal stem rot (BSR) is the most devastating oil palm disease caused by Ganoderma
boninense. It is only evident when the infection has progressed by 60–70% which is too late to cure
the palm. Studies on early defense responses are required to provide insightful information on the
initiation of defense signaling networks upon recognition of pathogen. Thus, information on early
interactions of plant-pathogens is crucial to allow screening for detection of the potential
threat of BSR, especially on young palms. This study was conducted to isolate and
detect the presence of G. boninense within infected oil palm seedlings, and to identify
the differentially expressed genes (DEGs) which related to pathogenesis (PR) as well as to
analyse PR genes expression in oil palm roots as a result of oil palm-G. boninense interaction. Oil
palm seedlings were artificially infected with G. boninense inoculums. Deoxyribonucleic acid
(DNA) samples were taken from infected palms (T1) and G. boninense pure culture for detection
using polymerase chain reaction (PCR), multiple sequence alignment (MSA) and basic local
alignment search tool (BLAST) via NCBI. Polymerase chain reaction (PCR) and nested PCR produced
amplicon with the expected size of 200 base pairs (bp) for 3 days post-inoculation (DPI) and G.
boninense pure culture, as well as 100 bp for 7 and 11 DPI. MSA showed the presence of the
conserved sequence and ≥95% identity generated via BLAST for all amplicons of T1 samples and G.
boninense pure culture. Ribonucleic acid (RNA) samples were extracted from the root tissues at
different periods (0, 3, 7, 11 DPI) and used for ribonucleic acid sequencing (RNASeq) analysis.
DEGs were identified. DEGs analyses displayed that several PR proteins were expressed as a
result of the defense mechanism of oil palm against
G. boninense including chitinase 1 isoform X3 (EgChi1X3), germin-like 8-14 (EgGer8), glu S.
griseus protease inhibitor (EgGluP), glucan endo-1,3-beta-glucosidase 3-like (EgGlu3) and
subtilisin-like protease SBT1.9 (EgPro1.9). These genes were searched for primary structural
homology via BLAST, based on size and exon count. Homology searches for selected PR genes
with their respected PR groups generated. The conserved domain for each PR gene was analysed
to determine their functions in terms of plant defense. MSA was done and generated a
phylogenetic tree for each PR gene to check their related grouping based on the conserved
domain. MSA generated ≥ 90% of primary structural homology among selected genes with their respected PR groups. Based on
conserved domains, each PR gene function was determined which is related to plant
defense. EgChi1X3 may be involved in the production of elicitor compounds and the
degradation of fungal chitins. EgGer8 is probably involved in oxidative degradation of oxalate
and preventing plant cell wall hydrolysis. EgGluP may be involved in promoting inhibition of
pathogen proteolytic enzymes. EgGlu3 is possibly related directly to the activity of
degradation and rendering fungal cell walls susceptible to plant responses and cell lysis. EgPro1.9
may be involved in extracellular protein secretion and mature peptide degradation. The defense
response obtained from DEG analyses showed immense upregulation of EgChi1X3, EgGer8 and
EgGluP with an average of 12, 3 and 32-fold higher than control at 3 DPI. While EgGlu3 and
EgPro1.9 significantly expressed with 218 and 6-fold at 11 DPI when compared to control. The
phylogenetic tree showed that the selected PR genes were clustered together with date palm due to
probable motif similarity and sequence homology. Based on this study, these selected PR genes will
be potential candidates in developing biomarkers for early phase detection of G. boninense
infection. |
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