Juvenile hormone induces reproduction via miR-1175-3p in the red imported fire ant, Solenopsis invicta

Juvenile hormone(JH)acts in the regulation of caste differentiation between queens and workers(i.e.,with or without reproductive capacity)during vitellin synthesis and oogenesis in social insects.However,the regulatory mechanisms have not yet been elucidated.Here,we identified a highly expressed microRNA(miRNA),miR-1175-3p,in the red imported fire ant,Solenopsis invicta.We found that miR-1175-3p is prominently present in the fat bodies and ovaries of workers.Furthermore,miR-1175-3p interacts with its target gene,broad-complex core(Br-C),in the fat bodies.By utilizing miR-1175-3p agomir,we successfully suppressed the expression of the Br-C protein in queens,resulting in reduced vitellogenin expression,fewer eggs,and poorly developed ovaries.Conversely,decreasing miR-1175-3p levels led to the increased expression of Br-C and vitellogenin in workers,triggering the“re-development”of the ovaries.Moreover,when queens were fed with JH,the expression of miR-1175-3p decreased,whereas the expression of vitellogenin-2 and vitellogenin-3 increased.Notably,the suppression of fertility in queens caused by treatment with agomir miR-1175-3p was completely rescued by the increased vitellogenin expression induced by being fed with JH.These results suggest the critical role of miR-1175-3p in JH-regulated reproduction,shedding light on the molecular mechanism underlying miRNA-mediated fecundity in social insects and providing a novel strategy for managing S.invicta.

The temporal-spatial expression and functional analysis of three gustatory receptor genes in Solenopsis invicta using sweet and bitter compounds

The insect gustatory system participates in identifying potential food sources and avoiding toxic compounds.During this process,gustatory receptors(GRs)recognize feeding stimulant and deterrent compounds.However,the GRs involved in recognizing stimulant and deterrent compounds in the red imported fire ant,Solenopsis invicta,remain unknown.Therefore,we conducted a study on the genes SinvGR1,SinvGR32b,and SinvGR28a to investigate the roles of GRs in detecting feeding stimulant and deterrent compounds.In this current study,we found that sucrose and fructose are feeding stimulants and the bitter compound quinine is a feeding deterrent.The fire ant workers showed significant behavior changes to avoid the bitter taste in feeding stimulant compounds.Reverse transcription quantitative real-time polymerase chain reaction results from developmental stages showed that the SinvGR1,SinvGR32b,and SinvGR28a genes were highly expressed in fire ant workers.Tissue-specific expression profiles indicated that SinvGR1,SinvGR32b,and SinvGR28a were specifically expressed in the antennae and foreleg tarsi of workers,whereas SinvGR32b gene transcripts were also highly accumulated in the male antennae.Furthermore,the silencing of SinvGRI or SinvGR32b alone and the co-silencing of both genes disrupted worker stimulation and feeding on sucrose and fructose.The results also showed that SinvGR28a is required for avoiding quinine,as workers with knockdown of the SinvGR28a gene failed to avoid and fed on quinine.This study first identified stimulant and deterrent compounds of fire ant workers and then the GRs involved in the taste recognition of these compounds.This study could provide potential target gustatory genes for the control of the fire ant.