Study Of The UV-B Radiation Effects On The Leaves And Millet Color Of Foxtail Millet

Millet is the hulled grains of foxtail millet,which is originated in China.It has a profound influence on dryland agriculture in China.Millet color,an important indicator,can directly reflect the quality of foxtail millet.In this study,two varieties of 110 and Qinhuang 2(QH)were selected as the experimental material,and the effects of different treatment of UV-B radiation on the photosynthetic pigments and enzymes activity of the seedlings were studied.The millet color,total carotenoid contents and its components of lutein and zeaxanthin contents in grains under different intensity of UV-B radiation were determined and analyzed.The key genes were selected from the transcriptome level,and their expression profile were comparatively analyzed in grains of different varieties at different development stages.In this study,the effects of UV-B radiation on leaves and millet color of were explored,it lays a theoretical foundation for cultivating high quality and carotenoid content millet varieties in the future,and the main results were as follows:(1)Physiological and biochemical responses in the seedlings of foxtail millet to the UV-B radiation stress.The contents of carotenoids and chlorophyll in the leaves of two variety seedlings under UV-B ±treatments were all lower than control.The activities of SOD and POD were increased gradually with the time going by under the treatment of UV-B+,but the changes of their activities were irregular under the treatment of UV-B-.The activity of CAT was increased with the increasing of UV-B radiation intensity,and the MDA were both increased under UV-B± treatments.(2)The color and the contents of carotenoids in the millet affected by different intensity of UV-B radiation treatments.The colorimeter was used to determine the millet color of two varieties at different development stages under different intensities of UV-B radiation.The results showed that the value of L*a*b* indicators and the contents of total carotenoids,lutein and zeaxanthin of the UV-B-treated group were all lower than that of the control group.The value of indicator b* can represent the yellowness of millet color.The total carotenoids and its components contents in millets under different UV-B radiation treatments were compared and analyzed.The contents of total carotenoids,lutein and zeaxanthin in millet of the UV-Btreated group were lower than that of the control group.The main components of carotenoids in foxtail millet were lutein and zeaxanthin.(3)The transcriptome analysis of millet under different UV-B radiation treatments.The transcriptome in millet of two varieties under different UV-B radiation treatments were analyzed.Finally,3113 differentially expressed genes were screened out from 110 varieties,in which up-regulated genes accounted for 57.02% and down-regulated genes accounted for 42.98%.Ninety-six differentially expressed genes were screened out from QH,in which 47.92% were up-regulated and 52.08% were down-regulated.There were 3039 differentially expressed genes in 110 varieties and 90 differentially expressed genes in QH.Through the analysis of transcriptome sequencing results,15 key genes related to the formation of millet color were selected,and the expression patterns of these genes in 110 and QH showed some differences.(4)The analysis of expression patterns of carotenoid related genes induced by UV-B.Under different UV-B treatment,the expression patterns of the key genes in grains of foxtail millet at different development stages were analyzed by q RT-PCR.The results showed high correla tion with the transcriptional sequencing results.The results showed that while the genes of Seita.3G397800,Seita.2G303000,Seita.4G263300 and Seita.9G131200 were down-regulated with reducing of UV-B intnesity,the genes of Seita.9G047500,Seita.9G187300 and Seita.3G352300 were up-regulated.