A maize lipid droplet-associated protein is modulated by a virus to promote viral multiplication and infection

Pathogen infection induces massive reprogramming of host primary metabolism. Lipid and fatty acid metabolism is generally disrupted by pathogens and co-opted for their proliferation. Lipid droplets (LDs) that play important roles in regulating cellular lipid metabolism are utilized by a variety of pathogens in mammalian cells. However, the function of LDs during pathogenic infection in plants remains unknown. We show here that infection by rice black streaked dwarf virus (RBSDV) affects the lipid metabolism of maize, which causes elevated accumulation of C18 polyunsaturated fatty acids (PUFAs) leading to viral proliferation and symptom development. Overexpression of one of the two novel LD-associated proteins (LDAPs) of maize (ZmLDAP1 and ZmLDAP2) induces LD clustering. The core capsid protein P8 of RBSDV interacts with ZmLDAP2 and prevents its degradation through the ubiquitin-proteasome system mediated by a UBX domain-containing protein, PUX10. In addition, silencing of the ZmLDAP2 down-regulates expression of fatty acid desaturase genes in maize, leading to a decrease in C18 PUFAs levels and suppression of RBSDV accumulation. Our findings reveal that the plant virus recruits LDAP to regulate cellular fatty acid metabolism to promote viral multiplication and infection. These results expand the knowledge of the LD functions and viral infection mechanism in plants.