| G.biloba is an economic tree species with rich resources in China.The flavonoids in its leaves have high medicinal value.The research on improving the flavonoid yield of G.biloba leaves by regulating environmental factors has been widely carried out,but there are few studies on the effects of light quality on the growth and flavonoid accumulation of G.biloba,and there are no reports on the regulation mechanism of light quality on the secondary metabolism of G.biloba.In this study,the annual ginkgo seedlings were used as experimental materials,the light conditions were strictly controlled by LED,and three light quality treatments were set up,namely red light,mixed light(red: blue = 1:1)and blue light.With white light as the control,the effects of different light quality on the growth characteristics,photosynthetic parameters and flavonoids accumulation of ginkgo seedlings were explored.Through transcriptome sequencing,bioinformatics analysis and other methods,combined with the conclusions of previous studies.The metabolic mechanism of flavonol biosynthesis in G.biloba under red and blue light quality was preliminarily analyzed,which laid a foundation for the application of light quality in the cultivation of leaf G.biloba.The main results of this study are as follows:(1)Under different light quality,the seedling height of G.biloba is B > W > R > M.That is,blue light can significantly improve the seedling height of G.biloba,and Ginkgo 4# can reach22.85 cm,while the seedling height of G.biloba under red light and mixed light is relatively reduced.The ground diameter of G.biloba seedlings in the treatment group did not change significantly under light quality.In terms of biomass accumulation and distribution,treatment groups were not conducive to the accumulation of ginkgo leaf biomass and total biomass,and relatively reduced the leaf mass ratio;Red and mixed light were beneficial to the distribution of Ginkgo biomass to the root;Blue light is conducive to the allocation of Ginkgo biomass to the stem.Different light quality had significant effects on the morphology of G.biloba leaves,and its leaf width and leaf area were relatively large under white light;The petiole of G.biloba elongated significantly under red light;The light quality of the treatment group can improve the leaf moisture content to a certain extent.(2)With the increase of culture time,the chlorophyll content of G.biloba leaves increased as a whole;Compared with white light,mixed and blue light can significantly increase the content of total chlorophyll and carotenoid,while red light has the opposite effect;The net photosynthetic rate and transpiration rate of G.biloba leaves were at a high level under white light;The stomatal conductance of G.biloba leaves decreased significantly under mixed and blue light;Under different light quality,the variation range of intercellular CO2 concentration in G.biloba leaves is relatively small,and the overall blue light and white light are at a relatively high level.(3)In the first 6 weeks,the light quality of the treatment groups were more conducive to the accumulation of soluble sugar in G.biloba leaves than that of white light;After that,the content of soluble sugar accumulated and increased under white light,which was at the same level as that under red light,which was significantly higher than that under mixed and blue light treatment.On the whole,mixed and blue light could significantly increase the soluble protein content of G.biloba leaves;Under red light,the results are slightly different due to different test materials.The soluble protein content of Ginkgo 16# under red light is increased,while Ginkgo 4# and 3# are on the contrary.(4)The contents of quercetin,kaempferol and total flavonol glycosides in G.biloba leaves showed the same regularity under different light quality,that is,B > M > W > R,blue light and mixed light can always significantly improve the contents of these three,while red light is the opposite.The content of isorhamnetin in different light quality showed that mixed and blue were at the same level,and increased significantly relative to white light;The red light is mostly lower than the white light,but it does not reach a significant level.Comprehensive analysis of the effect of light quality on the flavonoid yield of G.biloba showed that blue light could significantly increase its yield(Ginkgo 16#,4#,3# were 0.76,0.65 and 0.89 times higher than white light respectively),and the flavonoid yield of G.biloba 16# could reach the highest 14.89 mg. PAL and C4 H enzyme activities during phenylpropane metabolism were consistent with their total flavonols,while 4CL enzyme activity did not change significantly under light quality in the treatment group.The results of total reducing power of flavonoids extract showed that mixed and blue light significantly improved the total reducing power of G.biloba leaves,while red light was at the same level as white light treatment.(5)A total of 1840 DEGs were identified by transcriptome sequencing.The results of GO analysis of differential genes showed that the most annotated items of DEGs were ‘catalytic activity’,and the ‘inherent components of membrane’ were jointly enriched among the three comparison groups.KEGG notes that the most items of DEGs are ‘Biosynthesis of other secondary metabolites’.The metabolic pathways jointly enriched among the three comparison groups include‘Flavonoid biosynthesis’ and ‘Protein processing in endoplasmic reticulum’,and the largest number of DEGs in ‘Flavonoid biosynthesis’ pathway is 40,involving 13 related metabolic enzymes.(6)Transcription factors Gb＿12012(HY5)、Gb＿39081(MYB)and structural genes CHS(Gb＿20355)、F3H(Gb＿29563)、FLS(Gb＿14028、Gb＿14029、Gb＿14030)in G.biloba leaves can positively regulate the biosynthesis of flavonol,while Gb＿27262(MYB＿related)、Gb＿34639(MYB＿related)plays a negative regulatory role.Combined with the existing research and the results of this experiment,it is preliminarily speculated that the mechanism of Ginkgo response to red and blue light quality: after G.biloba leaves are stimulated by red and blue light,Gb＿12012 expression changes the abundance of HY5 and affects the expression level of downstream MYB family related transcription factors.MYB directly binds to the promoters of structural genes CHS,F3 H and FLS(some transcription factors of b HLH,B3 and NAC family may also bind to MYB to participate in this process),so as to regulate its expression to promote(or inhibit)the biosynthesis of flavonols in leaves.Finally,the flavonol content of G.biloba leaves increased relatively under blue and mixed light,but decreased relatively under red light. |
PDF Full Text Request