Differential immune responses of Monochamus alternatus against symbiotic and entomopathogenic fungi

Monochamus alternatus, the main vector beetles of invasive pinewood nematode, has established a symbiotic relationship with a native ectotrophic fungal symbiont, Sporothrix sp. 1, in China. The immune response ofM. alternatus to S. sp. 1 in the coexistence of beetles and fungi is, however, unknown. Here, we report that immune responses ofM. alternatus pupae to infection caused by ectotrophic symbiotic fungus S. sp. 1 and entomopathogenic fungus Beauveria bassiana differ significantly. The S. sp. 1 did not kill the beetles while B. bassiana killed all upon injection. The transcriptome results showed that the numbers of differentially expressed genes in M. aIternatus infected with S. sp. 1 were 2-fold less than those infected with B. bassiana at 48 hours post infection. It was noticed that Toll and IMD pathways played a leading role in the beetle＇s immune system when infected by symbiotic fungus, but upon infection by entomopathogenic fimgus, only the Toll pathway gets triggered actively. Furthermore, the beetles could tolerate the infection of symbiotic fungi by retracing their Toll and IMD pathways at 48 h. This study provided a comprehensive sequence resource ofM. alternatus transcriptome for further study of the immune interactions between host and associated fungi.

Monochamus alternates,the main vector beetles of invasive pinewood nematode,has established a symbiotic relationship with a native ectotrophic fungal symbiont,Sporothrix sp.1,in China.The immune response ofM.alternates to S.sp.1 in the coexistence of beetles and fungi is,however,unknown.Here,we report that immune responses ofM.alternates pupae to infection caused by ectotrophic symbiotic fungus S.sp.1 and entomopathogenic fungus Beauveria bassiana differ significantly.The S.sp.1 did not kill the beetles while B.bassiana killed all upon injection.The transcriptome results showed that the numbers of differentially expressed genes in M.alternates infected with S.sp.1 were 2-fold less than those infected with B.bassiana at 48 hours post infection.It was noticed that Toll and IMD pathways played a leading role in the beetle's immune system when infected by symbiotic fungus,but upon infection by entomopathogenic fungus,only the Toll pathway gets triggered actively.Furthermore,the beetles could tolerate the infection of symbiotic fungi by retracing their Toll and IMD pathways at 48 h.This study provided a comprehensive sequence resource ofM.alternates transcriptome for further study of the immune interactions between host and associated fungi.