Physiological Characteristics And Transcriptomic Analysis Of Seed Development Of Picea Mongolica

Picea mongolia is a rare and precious spruce species in my country.Its main root is shallow,lateral roots are developed,and the fibrous roots under the main trunk are often arched and semi-bare on the ground to extend around,which can gather the scattered fine quicksand around it.Excellent cold resistance,drought resistance and other characteristics have become the main species in the Hunshandake sandy ecosystem,forming a unique sandy forest and grassland.In this thesis,the seeds of six developmental stages(S1-S6)of Picea mongolia are used as experimental materials to explore the changes in the development of Picea mongolia seeds from the morphological,cytological and transcriptomic levels.The identification of key genes of Picea mongolia seed development and the genetic improvement of seed traits provide theoretical basis for related research.Important findings are as follows:(1)Determination of the longitudinal diameter,transverse diameter and thickness of Picea mongolia seeds and the calculation of seed volume and sphericity,the results show that the longitudinal diameter and transverse diameter of S.,seed volume and seed sphericity reach the maximum value,and the morphological indicators are the minimum in the S1 period.There are roughly four periods of Picea mongolia seed growth and development,showing the "slow growth-fast growth-slow growth-slow decline".By measuring the fresh weight and dry weight of the seeds and calculating the thousand-kernel weight and water content of the seeds,the results show that the thousand-kernel weight of the Picea mongolia seeds reaches the maximum value and the water content decreases to the minimum in the S6 period.The highest,the accumulation of Picea mongolia seeds has two important periods,showing the trend of "slow accumulation-rapid accumulation".(2)Observing the color and luster of the seeds,it was found that the color of the seeds changed from light to dark with the development of the seeds,and finally changed from milky white to dark brown.At the same time,the seed coat structure also became dense and hard;As the seed develops,the cell volume increases,and the arrangement between cells changes from irregular to neat.During this process,the cytoplasm becomes thicker,the staining deepens,the cell wall thickens,and the lignin content increases.(3)With the development of Picea mongolia seeds,the MDA content in the seeds showed a downward trend,and the MDA content in the S1 stage was significantly higher than that in other stages;the SOD and POD enzyme activities showed a trend of first increasing and then decreasing.In the early stage of development,the enzyme activities of SOD and POD reached the maximum in S2 and S4 stages respectively;the soluble protein content in Picea mongolia showed an increasing trend,and the protein content reached the maximum in S6 stage;the content of soluble sugar in Picea mongolia The trend of first decreasing and then increasing,soluble starch showed a trend of first increasing and then decreasing.Contrary to sugar,sugar content decreased to the lowest in S4 period,while starch reached the highest;the electrical conductivity and relative electrical conductivity of Picea mongolia showed The trend of increasing first and then decreasing,the conductivity and relative conductance reached the maximum in the S5 period,and then suddenly decreased to the minimum in the S6 period.(4)A total of 3167.9M of original reads were measured by transcriptome sequencing,and 3094.8M of low-quality reads generated by filtering out the sequencing,|log2Fold Change|>1,padj<0.01 as the screening criteria,in SDYS4 vs SDYS2,SDYS6 vs SDYS2,In SDYS6 vs SDYS4,11,588,22,093,and 16,443 significantly expressed differential genes were identified,of which 5,177,9,261,and 6,975 were up-regulated,and 6,411,12,832,and 9,468 were down-regulated.Comparing SDYS6 vs SDYS2,691 transcription factor genes were obtained,and these transcription factors were involved in 52 transcription factor families.By screening the differentially expressed genes and performing functional enrichment analysis on them,it was found that the differentially expressed genes related to plant hormones,starch and sucrose,as well as proteins,antioxidant enzymes and membrane lipid peroxides regulated the maturation process of Picea mongolia seeds.Seven genes related to the regulation of seed development were selected for q RT-PCR experiments.The results showed that the expression patterns of these seven genes were consistent with the transcriptome sequencing results,and the transcriptome sequencing results were accurate.