Transcriptomic Analysis On The Function Of Tissue-specific Arabidopsis UV-B Photoreceptor

As an important environmental factor,the ultraviolet-B(280-315nm)has an effect on the morphogenesis and growth of plants.Low-intensity and long-wavelength UV-B is able to induce plant photomorphohgenesis,including inhibition of hypocotyl elongation,anthocyain and flavonoid biosynthesis,to increase the abiliy to resist and acclimatize to UV-B.UV RESISTENCE LOCUS8(UVR8)has been identifed as a UV-B photoreceptor,which mediates the response reaction to UV-B in plants.Without UV-B radiation,the UVR8 protein usually exists in a homodimer form.The UVR8 homodimer dissociates immediately to generate a monomer form upon UV-B radiation,initiating the UV-B signaling.Prievious researches have shown that the UVR8 protein is widely distributed around the whole Arabidopsis,including root,stem,leafs and epidermis cells.However,It is still unclear that what biological effects the UVR8 has when it is expressed in diffferent tissues and cell types.In our early studies,we have constructed seven kinds of transgenic lines by expressing Yellow Fluorescent Protein(YFP)-UVR8 protein in various parts of uvr8-6 background.The acquisition of these transgenic plant materials is beneficial to the study on the functions of UVR8 upon UV-B expressed in different tissues.Therefore,we carried out the project in the following two aspects:(1)Through RNA-seq,the high throughout sequencing technology,we extracted and analyzed the differentially expressed genes(DEGs)at the whole genome level.By comparing the numbers of DEGs,we confirmed that the regulation ability of UV-B to gene expression is dependent on UVR8.The UVR8 protein expressed in the epidermis cells plays a vital role in UV-B response.Furthermore,we sorted out the genes which are inducible and UVR8-dependent under UV-B.We found the biological processes and metabolic pathways these genes involved in by performing GO and KEGG enrichment analysis.We also examined the expression patterns of the genes involved in acertain biological processes among different sequencing samples by clustering heatmap analysis.We validated our RNA-seq data by qRT-PCR and found there is a fine correlation.(2)The accumulation of anthocyanin and the flavonoid biosynthesis are the two canonical biological processes under UV-B radiation.Transcriptome data showed that UVR8 expression in the mesophyll and epidermic cells can induce the genes involved in anthocyanin metabolic pathway more strongly.Hence,we measured the content of anthocyanin,and proved that UVR8 expression in the mesophyll and epidermic cells is necessary for the UV-B induced anthocyanin accumulation.On the other hand,Transcriptome data indicated that UVR8 expression in the roots and epidermic cells is more powerful in regulating those genes which are necessary for the UV-B-induced flavonoid accumulation.Through DPBA staining,we further proved that UVR8 expression in the casparian strip and epidermic cells is necessary for the UV-B induced flavonoid accumulation.In conclusion,by performing bioinformatic analysis and molecular biology methods on tissue-specific UVR8 lines,we reveal that in UV-B photomorphogenesis,the common and unique biological processes which UVR8 photoreceptor in different tissues involved in.which tissue-specific UVR8 probably is involved in.We discovered which part of UVR8 is responsible for UV-B-induced anthocyain and flavonoid biosynthesis under UV-B.This research contributes to the study on the funcitions of tissue-specifc UVR8.The subsequent analysis of high throughout sequencing data will provide new ideas for tissues-specific UVR8 research in the future.