Functional Analysis Of Ar-HP1 In Artemia Diapause Embryos Formation

Artemia live in alpine saline lakes,evolved special reproductive patterns in order to adapt unfavourable conditions such as hypoxia,drought and hypersaline environments.With in favourable conditions,nauplii can be produced directly,while in unfavourable conditions Artemia produce embryos.The dormant embryos being produced can remain in a static state for a long time,which can be activated under low temperature.The specific mechanism of this phenomenon has not been fully clarified.Most of the cells in the diapause embryos of Artemia are in Quiescent state,and their nuclei are highly heterochromatinized.Based on this model with the characteristics of high heterochromatinization in embryonic cells,the formation process of quiescent embryos of Artemia was explored from the perspective of heterochromatin formation.In this study,we obtained the heterochromatin protein 1(Ar-HP1)from the transcriptome database of Artemia.The complete sequence of Ar-HP1 was obtained by cloning methods,and the multi-species comparison and phylogenetic tree analysis were fallowed.Quantitative analysis of Ar-HP1 in different stages of Artemia embryos by specific primers shows that there was high expression in Diapause stage.Western blotting analysis using HP1? antibody shows that the expression of Ar-HP1 protein increased gradually during the formation of dormant embryos,and reached the peak at Diapause stage.The expression of Ar-HP1 increased along with the development of dormant embryos,and there was a tendency to locate it from extracellular to endonuclear.In order to verify the function of Ar-HP1 on the formation of diapause embryos of Artemia,the expression of Ar-HP1 was interfered by si RNA microinjection.The results show that Ar-HP1 m RNA level was decreased significantly after the intervention.Along with the change of reproductive mode of Artemia,the diapause embryos were changed from producing embryos to producing nauplii directly.In the meantime,we found that the expression of HP1 protein and the degree of heterochromatinization in nucleus of diapause embryos decreased after intervention,which shows that heterochromatinization played an important role in the formation of diapause embryos of Artemia.As an heterochromatin protein in Artemia,Ar-HP1 was involved in the heterochromatinization process during the formation of diapause embryos.If it can't express normally,it can't complete heterochromatinization smoothly,which results in the formation of diapause embryos being interrupted and the reproductive mode of Artemia changed.In conclusion,Ar-HP1,as an allochromatin protein of Artemia,plays an important role in the formation of heterochromatin.Its absence will lead to the incomplete heterochromatinization process.The formation of diapause embryos of Artemia along with the embryonic cells entering a diapause state,requires a large amount of heterochromatin formation and maintain.Therefore,Ar-HP1 plays an important role in the formation of diapause embryos of Artemia.The findings provide new ideas and data proof for further elucidating of the dormancy mechanism in Artemia.