Role of digestive protease enzymes and related genes in host plant adaptation of a polyphagous pest,Spodoptera frugiperda

The evolutionary success of phytophagous insects depends on their ability toefficiently exploit plants as a source of energy for survival.Herbivorous insects largelydepend on the efficiency,flexibility,and diversity of their digestive physiology and sophistication of their detoxification system to use chemically diverse host plants as foodsources.The fall armyworm,Spodoptera frugiperda(J.E.Smith),is a polyphagous pest ofmany commercially important crops.To elucidate the ability of this insect pest to adaptto host plant mechanisms,we evaluated the impact of primary(corn)and alternate(rice)host plants after 1l generations on gut digestive enzymatic activity and expression profiles of related genes.Results indicated that the total protease and classspecific trypsinand chymotrypsinlike protease activity of S.frugiperda significantly differed among hostplant treatments.The classspecifiq protease profiles greatly differed in S.frugiperdamidguts upon larval exposure to different treatments with inhibitors compared with treatments without inhibitors.Similarly,the single and cumulative effects of the enzymespecific inhibitors TLCK,TPCK,and E64 significantly increased larval mortality and reduced larval growth/mass across different plant treatments.Furthermore,the quantitativereverse transcription polymerase chain reaction results revealed increased transcription oftwo trypsin(SfTry3,SfTry7)and one chymotrypsin gene(Sfchym9),which indicatedthat they have roles in host plant adaptation.Knockdown of these genes resulted in significantly reduced mRNA expression levels of the trypsin genes.This was related to theincreased mortality observed in treatments compared with the dsRED control.This resultindicates possible roles of S.frugiperda gut digestive enzymes and related genes in hostplant adaptation.

Microbial changes and associated metabolic responses modify host plant adaptation in Stephanitis nashi

Symbiotic microorganisms are essential for the physiological processes of herbivorous pests,including the pear lace bug Stephanitis nashi,which is known for causing extensive damage to garden plants and fruit trees due to its exceptional adaptability to diverse host plants.However,the specific functional effects of the microbiome on the adaptation of S.nashi to its host plants remains unclear.Here,we identified significant microbial changes in S.nashi on 2 different host plants,crabapple and cherry blossom,characterized by the differences in fungal diversity as well as bacterial and fungal community structures,with abundant correlations between bacteria or fungi.Consistent with the microbiome changes,S.nashi that fed on cherry blossom demonstrated decreased metabolites and downregulated key metabolic pathways,such as the arginine and mitogen-activated protein kinase signaling pathway,which were crucial for host plant adaptation.Furthermore,correlation analysis unveiled numerous correlations between differential microorganisms and differential metabolites,which were influenced by the interactions between bacteria or fungi.These differential bacteria,fungi,and associated metabolites may modify the key metabolic pathways in S.nashi,aiding its adaptation to different host plants.These results provide valuable insights into the alteration in microbiome and function of S.nashi adapted to different host plants,contributing to a better understanding of pest invasion and dispersal from a microbial perspective.

Cradle for the newborn Monochamus saltuarius:Microbial associates to ward off entomopathogens and disarm plant defense

The Japanese pine sawyer,Monochamus saltuarius,as a beetle vector of Bur-saphelenchus xylophilus(pine wood nematode),is an economically important forest pest in Eurasia.To feed on the phloem and xylem of conifers,M.saltuarius needs to overcome various stress factors,including coping with entomopathogenic bacteria and also various plant secondary compounds(PSCs).As an important adaptation strategy to colonize host trees,M.saltuarius deposit eggs in oviposition pits to shield their progeny.These pits har-bor bacterial communities that are involved in the host adaptation of M.saltuarius to the conifers.However,the composition,origin,and functions of these oviposition pit bacteria are rarely understood.In this study,we investigated the bacterial community associated with M.saltuarius oviposition pits and their ability to degrade PSCs.Results showed that the bacterial community structure of M.saltuarius oviposition pits significantly differed from that of uninfected phloem.Also,the oviposition pit bacteria were predicted to be enriched in PSC degradation pathways.The microbial community also harbored a lethal strain of Serratia,which was significantly inhibited.Meanwhile,metatranscriptome anal-ysis indicated that genes involved in PSCs degradation were expressed complementarily among the microbial communities of oviposition pits and secretions.In vitro degrada-tion showed that bacteria cultured from oviposition pits degraded more monoterpenes and flavonoids than bacteria cultured from uninfected phloem isolates.Disinfection of ovipo-sition pits increased the mortality of newly hatched larvae and resulted in a significant decrease in body weight in the early stages.Overall,our results reveal that M.saltuarius construct oviposition pits that harbor a diverse microbial community,with stronger PSCs degradation abilities and a low abundance of entomopathogenic bacteria,resulting in the increased fitness of newly hatched larvae.