Nascent Polypeptide-Associated Complex Involved in the Development and Pathogenesis of Fusarium graminearum on Wheat

Reliable knowledge on pathogenic agents contributes to effective plant protection.For most plant pathogens,maintaining protein homeostasis(proteostasis)is essential for unfolding the cellular functions to survive and thrive.However,the fungal proteins involved in proteostasis remain poorly characterized in the process of pathogenesis.In this study,we characterized the function of the nascent polypeptideassociated complex(NAC)in Fusarium graminearum(F.graminearum)(FgNAC),one of the top 10 fungal pathogens with predominant scientific/economic importance.We found that FgNACa,a subunit of FgNAC,manifests high structural and functional similarity to its homologous counterparts in yeast and other species.The mutants of F.graminearum lacking NACa are viable but suffer significant defects in vegetative growth,conidial production,and pathogenesis.In addition,we show here that FgNACa can interact with another subunit of NAC(FgNACb)in a yeast-two-hybrid assay.The subcellular localization results show that FgNACa and FgNACb are predominantly localized in the cytoplasm.Future studies should focus on deciphering the mechanism by which NAC orchestrates protein biogenesis and consequentially modulates development and pathogenesis.

Crystal structures of NAC domains of human nascent polypeptide-associated complex (NAC) and its αNAC subunit

Nascent polypeptide associated complex(NAC)and its two isolated subunits,αNAC and βNAC,play important roles in nascent peptide targeting.We determined a 1.9Åresolution crystal structure of the interaction core of NAC heterodimer and a 2.4Åresolution crystal structure ofαNAC NAC domain homodimer.These structures provide detailed information of NAC heterodimerization and αNAC homodimerization.We found that the NAC domains of αNAC and βNAC share very similar folding despite of their relative low identity of amino acid sequences.Furthermore,different electric charge distributions of the two subunits at the NAC interface provide an explanation to the observation that the heterodimer of NAC complex is more stable than the single subunit homodimer.In addition,we successfully built a βNAC NAC domain homodimer model based on homologous modeling,suggesting that NAC domain dimerization is a general property of the NAC family.These 3D structures allow further studies on structurefunction relationship of NAC.