The essential role of clathrin-mediated endocytosis and early endosomes in the trafficking of begomoviruses through the primary salivary glands of their whitefly vectors.

Begomoviruses are significant constraints to the production of many crops worldwide. Efficient passage of the circulatively transmitted begomoviruses through the midgut and primary salivary gland (PSG) of their whitefly vector is an essential step in productive virus transmission. While how begomoviruses transport across the whitefly midgut wall has been characterized, the mechanisms underlying the trafficking of begomoviruses through whitefly PSG remain poorly understood. In this study, we combined direct injection of purified virions into the whitefly hemolymph with inhibitor and dsRNA treatment and investigated the roles of endocytosis and endosomes in the entry and intracellular trafficking of begomoviruses in whitefly PSG. We found that clathrin-mediated endocytosis and early endosomes mediated the entry of tomato yellow leaf curl virus (TYLCV) into whitefly PSG. Additionally, late and recycling endosomes were not involved in TYLCV trafficking in PSG. Notably, the regulating proteins of vesicle trafficking such as Arp2/3 complex; CORVET complex subunits Vps8, Vps11, and Vps33a; and sorting nexin Snx12 did not seem to play a role in TYLCV entry into PSG. Furthermore, clathrin-mediated endocytosis and early endosomes were found to mediate the entry of another begomovirus into PSG, indicating it might be a conserved pathway exploited by begomoviruses to enter PSG. Our results uncovered the key whitefly components that mediate the trafficking of begomoviruses in PSGs of their insect vectors. IMPORTANCE Many plant viruses are transmitted by insect vectors in a circulative manner. For efficient transmission, the entry of the virus from vector hemolymph into the primary salivary gland (PSG) is a step of paramount importance. Yet, vector components mediating virus entry into PSG remain barely characterized. Here, we demonstrate the role of clathrin-mediated endocytosis and early endosomes in begomovirus entry into whitefly PSG. Our findings unravel the key components involved in begomovirus transport within the whitefly body and transmission by their whitefly vectors and provide novel clues for blocking begomovirus transmission.