Genomic Study On Seasonal Egg Polyphenism Of Colocasiomyia Hailini

The gigantea species group is one of the six species groups of genus Colocasiomyia,the known species of which mainly distributed in Indonesia and Solomon Islands,Sabah,Malaysia and Yunnan,China.It is the only taxon that can use plants of subfamily Monsteroideae as the host so far.C.hailini and C.yini exhibiting peculiar reproductive habits for adaption to the flower structure and fruit formation of R.decursiva(Roxb.)Schott and R.lancifolia Schott.Compared with other Colocasiomyia species with monomorphic egg.C.hailini and C.yini break the original phenological synchrony with host plants and perform specific characteristics in the change of voltinism and two types of eggs:the filament of summer-type egg(S-type eggs)is only half of whole body,while it is almost equal in autumn-type egg(M-type eggs),with some significant differences occurring in morphology,larval feeding,oviposition between the two-type eggs.The distinct egg morphology and life history with different generations in C.hailini and C.yini demonstrated adaption to special environment,which show an excellent system to discuss genetic mechanisms of the adaptive evolution.The discoverd egg polymorphism in insects firstly provides us a new perspective for the further study on drive of polymorphism and epigenetic research,simultaneously.Our present study is conducted with establishment of isofemale lines,adults of isofemale line were then collected and sequenced by the next-generation sequencing platform to obtained genome data of C.hailini(egg dimorphy)and C.longifilamentata(egg monomorphy)(Genome sizes is 259.44 Mb vs 341.36 Mb,coverage is 245.56 X vs 231.29 X,and contig N50 is 48.10 Kb vs 21.46 Kb,scaffold N50 is 1.88 Mb vs 1.49 Mb,respectively).To investigate the evolutionary mechanism of seasonal egg dimorphy in C.hailini,we performed a comparative genomic analysis combined with other five published genomes of flies.Firstly,9,476 gene families and 2,796 orthologous genes were defined by seven species based on Treefam methodology.We constructed phylogenetic tree with all orthologous genes and was used as the outgroup,the phylogenetic tree supported C.hailini are grouped with C.longifilamentata with high confidence level.Divergence time was also estimated,the split between C.hailini and C.longifilamentata occurred at 8.6 Mya.We then detected gene familyexpansion and contraction in C.based on all gene families.A total of 287 significant expansion gene families(1404 genes)and 339 significant contraction gene families(1353 genes)were identified in C.hailini.GO enrichment for significant expansion gene families determined that Anaphase promoting complex(APC),Smc5-Smc6 complex,piRNA were related to cell cycle,chromosomal variation,germ cell activity,and increases in copy number might suggest that involving in the short life cycle and change of voltinism of C.hailini.Besides,we detected 220 genes in C.hailini under positive selection.It's remarkable that ACC,FAF,SHOT are associated with glucose and lipid metabolism,embryonic development and cell migration,respectively,which play important roles in egg dimorphy and filament specialization,possibly.In this study,the genome sequences of C.hailini and C.longifilamantata,which are representative species of Colocasiomyia were acquired firstly and were evaluated egg dimorphy of Colocasiomyia hailini at genome level.We focus on oviform character that has received little attention and found some genes related to oocyte develepment and phenotypic regulation,which contributed to a novel and complete understanding of the genetic mechanism of egg dimorphy,cluing for further function research,simultaneously.