Immune responses of the Asian onion moth, Acrolepiopsis sapporensis, and their genetic factors from RNA‐Seq analysis

Abstract

A nonmodel insect, Acrolepiopsis sapporensis, has been analyzed in immune responses. The total hemocytes in the fifth instar larvae were 2.33 × 106 cells/mL. These hemocytes comprised at least five different types and different relative ratios: 47% granulocytes, 26% plasmatocytes, 11% oenocytoid, 8% prohemocytes, and 5% spherulocytes. Upon bacterial challenge, some of the hemocytes exhibited typical hemocyte‐spreading behaviors, such as focal adhesion, and filopodial and lamellipodial cytoplasmic extensions. The hemocyte behaviors induced cellular immune responses demonstrated by nodule formation. In addition, the plasma collected from the immune‐challenged larvae exhibited humoral immune responses by bacterial growth inhibition along with enhanced phenoloxidase enzyme activity. These cellular and humoral immune responses were further analyzed by determining the immune‐associated genes from a transcriptome generated by RNA‐Seq. A total of about 12 Gb sequences led to about 218,116 contigs, which were predicted to encode about 46,808 genes. Comparative expression analysis showed 8392 uniquely expressed genes in the immune‐challenged larvae. Differentially expressed gene (DEG) analysis among the commonly expressed genes indicated that 782 genes were upregulated and 548 genes were downregulated in the expressions after bacterial challenge. These immune‐associated genes included pattern recognition receptors, immune mediation/signaling genes, and various immune effectors. Specifically, the genetic components of the Toll, IMD, and JAK/STAT immune signaling pathways were included in the DEG database. These results demonstrate the immune responses of A. sapporensis larvae and suggest the genes associated with the immune responses in this nonmodel insect.

Screening of insect immune suppressors using a recombinant phospholipase A2 of a lepidopteran insect

“…These results indicate that the metabolites did not change V max , but increased the K m values (Figure 5c), suggesting that their inhibitory action occurs in a reversible and competitive mode. Even though the inhibitors were tested against L5 larvae, they would give the inhibitory activities to other young larval stages due to the PLA 2 gene expressions in all developmental stages (Hrithik & Kim, 2023).…”

“…Among the different Bt strains, B. thuringiensis kurstaki was found to be the most effective one in killing A. sapporensis larvae (Hrithik & Kim, 2023). A bacterial extract (Ptt) containing bacterial metabolites produced by P. temperate temperata could significantly enhance the Bt virulence against the larvae (Figure 7a).…”

“…At 24 h of dsRNA (specific to As‐PLA 2 A ) injection, E. coli Top10 (Invitrogen) was injected into the 5th instar larvae in a dose of 10 4 cells/larva. After 8 h, the test insect hemocoel was dissected, and the resulting nodules were counted according to the method described by Hrithik and Kim (2023). Each treatment was replicated with five individuals.…”

“…Hemolymph was collected from L5 larvae of A. sapporensis and subsequently separated into hemocytes and plasma, as per the previously mentioned method (Hrithik & Kim, 2023). To measure the PO activity in the plasma, L‐3,4‐dihydroxyphenylalanine (DOPA; Sigma‐Aldrich) was employed as the substrate.…”

“…The Asian onion moth, Acrolepiopsis sapporensis , is native to eastern Asia, including China, eastern Russia, Japan, and Korea (Landry, 2007), and its larvae can induce serious economic damage to the Welsh onion crop (Park et al, 2012). Transcriptome analysis on A. sapporensis has provided the immune‐associated genes, ranging from the recognition genes to the effector ones (Hrithik & Kim, 2023). Four PLA 2 genes were identified with crucial roles in mediating immune responses in this species.…”