Identification And Transcriptome Analysis Of Seed Development-related Traits In Xanthoceras Sorbifoli

Yellow horn(Xanthoceras sorbifolium Bunge),Sapindaceae,mainly grows in northern China,and is a unique woody oil tree species in China.Its kernel can be made into edible oil and biodiesel,and other tissue parts also have specific utilization value.At present,there are few studies on the accumulation of contents and their dynamic changes during the fruit development of yellow horn in Northeast China.In this study,several yellow horn with similar growth in Northeast Forestry University(126°E,45°N),was used as experimental materials to analyze the morphological changes,contents and physiological indexes of fruit development.Transcriptome sequencing technology was used to predict the genes involved in oil synthesis with two seed coats and four seed kernels as materials.It is helpful to clarify the growth and development law of yellow horn in Heilongjiang Province and lay a foundation for improving the utilization rate of fruit.The results are as follows:1.The fruit period of yellow horn in Heilongjiang Province is usually from June to September,and the fruit growth presents three stages: slow-fast-slow.The first stage is from flowering to DAF 20(June 15 th,2022),and the fruit develops slowly.From DAF40 to DAF 60(from July 5 to July 25,2022),the fruit entered the stage of rapid development,during which the transverse and longitudinal diameters of the fruit increased rapidly,and the transverse and longitudinal diameters reached more than 60 mm at this time.The kernel developed completely in 40 days.The third stage is a stable growth period from DAF 60 to DAF 80(August 14,2022).During this period,the horizontal and vertical diameters of yellow horn fruit developed slowly,the overall data remained basically stable,and the fruit size no longer changed.The fruit fully ripened around September 3,2022,and when it ripened,the shell cracked and the peel turned black.The development of seeds is similar to that of fruits.The seed coat begins to turn black at 60 days,and the fully mature seed coat becomes thinner and harder at 100 days.2.The results of seed dyeing in five developmental stages(DAF 20,DAF 40,DAF60,DAF 80 and DAF 100)of yellow horn showed that:(1)The starch content in seeds dyed by I2-KI method increased at first and then decreased.(2)The protein in seed coat was dyed by naphthol yellow staining method,and the protein distribution density generally showed a trend of increasing first and then decreasing.The Nile red staining method was used to dye lipids.Similar to protein,lipids also showed a trend of increasing first and then decreasing.According to the above-mentioned cell staining results,the observation trends of starch,protein and lipid contents in the kernel and seed coat of yellow horns are basically the same.3.The physiological indexes of seed kernel and seed coat of yellow horns at different stages of seed development were determined.The results showed that:(1)The content of soluble protein,soluble sugar and starch in yellow horn are internally transformed,which is consistent with the dyeing results.(2)The activities of antioxidant enzymes all showed a trend of increasing or increasing with development and then decreasing,among which the changes of peroxidase(POD)and ascorbate peroxidase(APX)were more prominent.(3)In addition,the determination of pyruvate content,organic acid content and cellulose content can also reflect the relationship between seed development and stress resistance.4.In this experiment,the second-generation transcriptome of four seed kernels and two seed coats at different stages was sequenced,and a total of 135.19 Gb Clean Data was obtained.Compared with the reference genome,eight groups(DAF 40 vs DAF 80,DAF 40 vs DAF 100,DAF 20＿SC vs DAF 40＿SC,DAF 40 vs DAF 40＿SC,DAF 40 vs DAF 60,DAF 80 vs DAF 100,DAF 60 vs DAF 100,DAF 60 vs DAF 80)has 29540 genes up-regulated and 24476 genes down-regulated,and a total of 36 genes are significantly expressed.According to KEGG enrichment analysis,13 genes related to fatty acid synthesis and 135 genes related to abiotic stress were found,among which one gene(EVM0017924)was involved in both fatty acid synthesis and abiotic stress response.In addition,five transcription factor families(MYB,WRKY,Ge BP,HSF and NF-X1)were predicted to play an important role in the transcription regulation of plant stress resistance.