Population density modulates insect progenitive plasticity through the regulation of dopamine biosynthesis

Insect fecundity is a quantitative phenotype strongly affected by genotypes and the environment.However,interactions between genotypes and environmental factors in modulating insect fecundity remain largely unknown.This study investigated the im-pact of population density on the fecundity of Nilaparvata lugens(brown planthopper;BPH)carrying homozygous high-(HFG)or low-(LFG)fecundity homozygous geno-types.Under low population densities,the fecundity and population growth rate of both genotypes showed similar increasing trends across generations,while the trends between HFG and LFG under high population densities were opposite.Through a combination of temporal analysis and weighted gene co-expression network analyses on RNA-seq data of HFG and LFG under low and high population densities in the lst,3rd,and 5th gener-ations,we identified 2 gene modules that were associated with these density-dependent progenitive phenotypes.Four pathways related to the neural system were simultaneously enriched by the 2 gene modules.Furthermore,Nlpale,which encodes a tyrosine hydroxy-lase,was identified as a key gene.The RNA interference of this gene and manipulation of its downstream product dopamine significantly affected the basic and density-dependent progenitive phenotypes of BPH.These findings indicated that dopamine biosynthesis is the key regulatory factor that determines fecundity in response to density changes in dif-ferent BPH genotypes.Thus,this study provides insights into the interaction of a typical environmental factor and insect genotype during the process of population regulation.