Effects Of Different Light Quality On Growth And Development Of Strawberry And Role Of FAHY5 In Quality Formation

Strawberry(Fragaria × ananassa Duch.)is a genus of strawberry in Rosaceae.It takes the first place in the production of small berries in the world.The advantages of small size and short growth period of fruit and high genetic transformation efficiency also make it a model plant for fruit research.Light environment is the most important environmental factor in protected culture.After light signal transduction,endogenous hormone changes will be caused,which will affect plant nutrient absorption,disease resistance and metabolism and other life activities.The low-light environment in the facility is one of the main restrictive factors for strawberry production,which ultimately affects the formation of the light morphology of the strawberry,the growth and development of the fruit,and it is easy to cause serious problems such as poor strawberry fruit quality and low yield.Therefore,it is of great significance to explore the effects of different light on the growth and development of strawberry in facility cultivation,as well as the role of light signal transduction factors in the formation of strawberry quality.In this study,different light qualities are used to complement the strawberry cultivated in facilities to study the effects of these light qualities on the strawberry’s morphology and quality formation.Through bioinformatics analysis,the light signal transduction factor FaHY5 was screened and its influence on strawberry fruit quality was explored by means of instantaneous transformation technology.1.The light test consisted of red light,blue light,ultraviolet light,white light,red light and blue(3:1,5:1,7:1,the number ratio of different color lights),and white light was used as the control.The octoploid cultivar"Benihoppe" strawberry was used as experimental materials and the strawberry cultivated in greenhouse was supplemented with different light.The morphological index,quality and antioxidant enzyme activity of the treated strawberry were measured.The results showed that the number of strawberry leaves,photosynthetic pigment synthesis,vitamin C and soluble protein content in the fruit were the highest under blue light treatment,but the elongation of plant height and CAT enzyme activity wereinhibited to a certain extent;Under red light treatment,strawberry plant height,petiole and stem diameter increased significantly,fruit soluble solids and soluble sugar contents were higher than those of the control,and antioxidant enzyme activities such as SOD,POD,APX were significantly increased;Under UV-B radiation,the fruit quality and morphology of strawberry could not achieve the ideal effect of supplementing light,and the activity of antioxidant enzymes was inhibited to different degrees;The morphological indexes of strawberry plants were optimized under the combination of red and blue light.Although the promotion effect of red:blue(3:1)on petiole length and stem diameter was less than that of red light,the number of leaves in plant height reached the highest level.When the ratio of red light was higher,the leaf area under red:blue(7:1)treatment was the largest.The results showed that red and blue combined light was more beneficial to fruit growth and quality formation than monochromatic light.red:blue(7:1)treatment had the largest single fruit weight,and the red:blue(3:1)treatment had the best effect on improving soluble sugar content,and the fruit skin gloss was also higher than other indexes.Based on the research results,the use of red:blue(3:1)to supplement light for protected strawberries is more conducive to the growth and development of plants and the formation of fruit quality.2.A bZIP transcription factor family member was selected from forest strawberry.Phylogenetic tree cluster analysis showed that the FvHY5 is highly homologous to AtHY5.Promoter analysis showed that multiple light responsive cis-acting element exists in the promoters of FvHY5,such as G-box,GT1-box,I-box and as so on.Through homologous cloning,the cDNA sequence of the gene obtained from the octoploid strawberry"Benihoppe" is 501 bp in length and named FaHY5.The homology degree with FvHY5 is as high as 99%,indicating that the gene structure is almost identical.FaHY5 is expressed in all tissues of strawberry,with the highest expression level in flowers,but lower expression levels in roots and fruits.FaHY5 gradually accumulated in the early growth and development stages of strawberry fruit,reached the highest level in the big green fruit stage,and decreased regularly in the later stages,indicating that the early growth and development stage of strawberry fruit was an important period of photomorphogenesis.In order to verify the correctness of light-responsive gene screening,the FaHY5 expression level under different light quality treatments was analyzed.The results showed that FaHY5 can be induced by blue,UV-B,and red and blue combined light,while red light has little effect on FaHY5 expression.3.Analyze the changes in the growth,quality and maturation-related gene expression of strawberry fruits after the overexpression of FaHY5.Through phenotypic observation and quality determination,the overexpression of FaHY5 gene can make strawberry fruits turn color and soften in advance,promote the ripening of strawberry fruits,and the contents of sucrose,fructose,vitamin C and anthocyanin in fruits are significantly increased.After gene overexpression,the expression of strawberry fruit ripening-related genes is regulated to varying degrees,including sugar metabolism genes FaSUS1/2,FaSPS2,FaSUT1,fruit softening and pigment-related genes FaEXP1,FaEXP3,FaXYL1,FaCHS,hormone metabolism genes FaJAZ1,FaJAZ2,FaJAZ8,FaMYC2,FaOPR3 and FaPYL1,FaPYL8,FaPYL9 changed most significantly.Comprehensive research results speculate that FaHY5 gene may regulate strawberry fruit ripening and quality formation by affecting the ripening-related sugar metabolism genes,fruit softening genes and hormone metabolism genes.