Lipid droplets (LDs) are dynamic organelles that participate in the regulation of lipid metabolism and cellular homeostasis inside of cells. LD-associated proteins, also known as perilipins (PLINs), are a family of proteins found on the surface of LDs that regulate lipid metabolism, immunity, and other functions. In silkworms, pébrine disease caused by infection by the microsporidian
Nosema bombycis
(
Nb
) is a severe threat to the sericultural industry. Although we found that
Nb
relies on lipids from silkworms to facilitate its proliferation, the relationship between PLINs and
Nb
proliferation remains unknown. Here, we found
Nb
infection caused the accumulation of LDs in the fat bodies of silkworm larvae. The characterized perilipin1 gene (
plin1
) promotes the accumulation of intracellular LDs and is involved in
Nb
proliferation.
plin1
is similar to
perilipin1
in humans and is conserved in all insects. The expression of
plin1
was mostly enriched in the fat body rather than in other tissues. Knockdown of
plin1
enhanced
Nb
proliferation, whereas overexpression of
plin1
inhibited its proliferation. Furthermore, we confirmed that
plin1
increased the expression of the
Domeless
and
Hop
in the JAK-STAT immune pathway and inhibited
Nb
proliferation. Taken together, our current findings demonstrate that
plin1
inhibits
Nb
proliferation by promoting the JAK-STAT pathway through increased expression of
Domeless
and
Hop
. This study provides new insights into the complicated connections among microsporidia pathogens, LD surface proteins, and insect immunity.
IMPORTANCE
Lipid droplets (LDs) are lipid storage sites in cells and are present in almost all animals. Many studies have found that LDs may play a role in host resistance to pathogens and are closely related to innate immunity. The present study found that a surface protein of insect lipid droplets could not only regulate the morphological changes of lipid droplets but also inhibit the proliferation of a microsporidian pathogen
Nosema bombycis
(
Nb
) by activating the JAK-STAT signaling pathway. This is the first discovery of the relationship between microsporidian pathogen and insect lipid surface protein perilipin and insect immunity.