| Euseius nicholsi(Ehara et Lee)belonging to the Phytoseidae,is an important predatory mite,main predator Tetranyus urticae,Panonychus citri,Panonychus ulmi and other agricultural pest mites.E.nicholsi has the biological characteristics such as fast reproduction,short life span and high fecundity,and has great application potential in biological control,but low cost propagation has not been realized to this day.Vitellogenin is the precursor of the major yolk protein vitellin(vn)in oviparous species,plays a decisive role in yolk formation and embryo formation,can be used as a marker to measure the reproduction ability of organisms.Knowing the relative expression level of Vg genes from E.nicholsi can quickly assess the suitability of this artificial feed.At present,there is no report of molecular information on the Vg genes of E.nicholsi.We tested the effect of different food on the spawning number and egg hatch rate of E.nicholsi,and reported the cloning and bio-informatics analysis of the En Vgl and En Vg2.The mRNA expression profile of Vg genes in different developmental stages and different food feeding were detected.The main results are as follows:?.Effect of different food on the spawning number and egg hatch rate of E.nicholsiE.nicholsi could lay eggs after mating,with a significant increase in daily fecundity,reaching the peak at the 4th day.Then daily fecundity started to drop rapidly.The total egg number for each female was influenced significantly by different food treatment.The P.citri-fed females laid the most eggs,reaching 22.47,which was 1.45-fold higher than females fed Camellia oleifera.But not significantly different from the Camellia japonica pollen fed group and Tetranychus cinnabarinus fed group.The hatching rate of eggs in all experimental groups were above 90%and not influenced significantly by difference food treatment(P>0.05).?.Analysis of the characteristics of the Vg genes sequence of E.nicholsiWe obtained the full-length cDNA of the EnVgl and En Vg2 and submitted them to NCBI(GenBank accession numbers:MN555331 and MK135169).The full-length of En Vgl and EnVg2 were 5734 and 5621 bp,the open reading frames were 5634 and 5538 bp,encoding 1877 and 1845 amino acids,respectively.According to the deduced amino acid sequence,the molecular weight of En Vg1 was 119.02 kDa with a proposed isoelectric point of 9.28,the molecular weight of EnVg2 was 211.57 kDa with a proposed isoelectric point of 9.13.EnVgl and EnVg2 protein sequences presented a typical GLCG characteristic motif,RTAR and RIRR cleavage sites,N-terminal lipid-binding domain,unknown functional region and von Willebrand factor D.The phylogenetic analysis shows that the Vg genes of Arachnida are clearly divided into two branches,one is Vg1 and the other is Vg2;EnVg1 was related most closely to Neoseiulus barkeri Vg1,while En Vg2 was related most closely to Neoseiulus cucumeris Vg2.?.The expression analysis of and at different developmental stagesEnVg1 and En Vg2 demonstrated the similar trend during the developmental stage.The expression level of En Vg1 and En Vg1 genes were hardly detectable from egg until the duetonymph stage,begin to be expressed in large quantities during the pre-oviposition stage,reaching a peak at the oviposition stage,the expression level of EnVgl is 6.11 and EnVg2 is 7.72.The mRNA concentration of EnVgl in oviposition was 3.79-and 20.34-fold higher than in the pre-oviposition and duetonymph,respectively.The mRNA concentration of EnVg1 in oviposition was 3.93-and 21.46-fold higher than in the pre-oviposition and duetonymph,respectively.These results indicated that En Vg1 and En Vg2 expression are closely related to yolk production.?.The expression profile analysis of and at different feeding foodThe females at different ages were collected from the different food feeding groups(P.citri-fed,T.cinnabarinus-fed,C.oleifera pollen-fed and C.japonica pollen-fed)at pre-oviposition stage and 2,4,6,8 days after mating.Females fed with P.citri had the highest expression level of EnVgl and EnVg2 in all treatment groups.With the extension of the mating time the expression of En Vgl and En Vg2 gradually increased,reaching a peak at the 4 day after mating,the expression level of EnVg1 is 1.14 and the expression level of EnVg2 is 1.42.Linear correlation analysis between daily fecundity and genes expression level in different food fed groups of E.nicholsi showed that the fecundity of females has a linear positive correlation with the expression level of En Vgl and EnVg2.This may indicate that vitellogenin has a certain effect on the spawning of E.nicholsi.In this study,we reported for the first time the genes sequences of EnVgl and EnVg1 and conducted mRNA expression pattern of genes.This lays the foundation for the subsequent research on the function of this genes,and also provides a certain theoretical basis for exploring the reproductive regulation of E.nicholsi. |
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