Understanding the effects of carbon and nitrogen starvation on the comparative secretomes of Ganoderma boninense and Ganoderma tornatum

Ganoderma boninense is the most pathogenic fungal species of oil palm trees. However, there is limited understanding of the host - pathogen interaction. Secreted proteins play a critical role during the early infection process which involves competition between the fungal and host populations for nutrient resources necessary for continual growth. To identify the secreted proteins that may play a role in pathogenicity during infection stage, we compared the secretome profiles of G. boninense versus G. tornatum under carbon and nitrogen starvation by using shotgun proteomics approach. In total, 250 non-redundant proteins were identified, and statistical data analysis indicated that 68 proteins were increased while 104 proteins decreased in abundance in T3 for G. boninense whereas in G. tornatum, 42 proteins were increased, and 27 proteins were decreased in abundance in T3. Further investigation via bioinformatic tools helped us to classify the carbohydrate-active enzymes (CAZymes) proteins into four classes: oxidoreductases, transferases, hydrolases, and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Interestingly, oxidoreductase enzymes were identified only in G. boninense. These putative proteins might contribute to the different levels of pathogenicity of G. boninense and G. tornatum toward oil palm. The newly discovered protein information may help researchers better understand the secretory mechanisms of G. boninense and the process by which it invades oil palm root tissues. The discovered seretome proteins, along with their subclassification and functional annotation also serve as a database for Ganoderma species that is easy to access and retrieve.