Cloning And Functional Analysis Of LEAFY Transcription Factor AaFL In Artemisia Annua L.

Artemisia annua L.(A.annua)is an annual herb of the family Asteraceae,which rich in a variety of secondary metabolites,including sesquiterpenes,monoterpenes,and triterpenoids.Among them,the sesquiterpene product artemisinin,a sesquiterpene lactone with an endoperoxide bridge,which has a unique therapeutic effect on the treatment of Plasmodium falciparum.Previous studies have shown that artemisinin is synthesized and stored in secretory glandular trichomes in leaves or flower buds of A.annua.The secretory glandular trichomes is composed of ten cells,including one pair of basal cells,one pair of stalk cells,three pairs of secretory cells.The artemisinin biosynthesis pathway genes ADS,CYP71AV1,DBR2 and ALDH1 are expressed in secretory glandular trichomes.The growth and development of glandular trichomes directly affects the yield of artemisinin.Therefore,studying the developmental mechanism and metabolic characteristics of glandular trichomes at the molecular level has important research significance for improving the content of artemisinin in A.annua plants.The plant flowering gene LEAFY(LFY)is a kind of transcription factor related to growth and development,which is responsible for regulating the formation and development of flower and plant reproductive and flowering stages.It has been reported that after overexpressing the LFY gene of chrysanthemum in the model plant Arabidopsis thaliana,the glandular trichomes are significantly inhibited,which provides us with new ideas for studying the regulation of transcription factors to regulate the glandular trichomes development of A.annua research direction.In this study,the LFY(AaFL)was cloned and the function of the gene was further studied.Firstly,the homologous gene AaFL was screened and cloned according to the chrysanthemum LFY(CmFL)sequence in the transcriptome of A.annua.Bioinformatics analysis,gene characteristics and expression characteristics were analyzed.Subcellular localization experiment proved that AaFL protein localization is expressed in the nucleus and is consistent with transcription factor localization characteristics.Secondly,in order to verify the biological function of AaFL gene,AaFL overexpressing Arabidopsis thaliana plants was constructed.The preliminary study in model Arabidopsis thaliana showed that AaFL gene has the function of regulating glandular trichomes development and biomass.Based on this,the in vivo function study of AaFL gene in A.annua was continued.After overexpression of the AaFL in A.annua,the density of glandular trichomes of A.annua.decreased,and the expression of genes related to glandular trichomes development of A.annua was down-regulated.The decrease in the expression level of the pathway gene indicates that AaFL negatively regulates the development of glandular trichomes,and also negatively regulates the biosynthesis of artemisinin at the genetic level.In summary,this paper preliminarily confirmed the negative regulation of AaFL in the development of the glandular trichomes of A.annua,and opened up a new research direction for the transcription factor network of the development of the glandular trichomes of A.annua.It is hoped that through the following research,the network of functions will be continuously improved,and the network of transcriptional factors regulating the development of the A.annua's glandular trichomes will be more clear.