Shell Structure Of Rice Tartary Buckwheat And Its Transcriptome Analysis During Development

Tartary buckwheat is rich in flavonoids,with many medical health effects such as anti-inflammatory,anti-oxidation,lower blood sugar,lower cholesterol and lower blood pressure.Tartary buckwheat products are more and more popular,but the difficulty of hulling restricts the development of tartary buckwheat.In this research,the cell structure and cost content of 4 thick shell buckwheat and 3 thin shell buckwheat in different periods were studied and analyzed,and the transcriptome sequencing analysis of the shells of "Jinqiao 2" and "Xiaomiqiao" in different development periods.The main results are as follows:?1?The results showed that the average content of cellulose,lignin and hemicellulose in thick shell tartary buckwheat is siginificantly higher than that of thin shell tartary buckwheat,especially the cellulose content in thick shell tartary buckwheat is much significantly higher than that of thin shell tartary buckwheat.Secondly,there are significant differences in the content of cellulose,lignin and hemicellulose among tartary buckwheat varieties with different shell types.?2?The results of SEM showed that the groove of "Xiaomiqiao" husk spontaneously cracked with obvious cracks on the surface,while the groove of "Jinqiao 2" husk did not crack and the surface had no cracks.The results of paraffin section showed that the the shell of "Xiaomiqiao" is close to the thickness of the shell of "Jinqiao 2" at the ridges,but their groove is thiner,which indicated that the difference of the thickness of the shell mainly occurred in the groove.Secondly,the cellulose content in the tissue is greatly reduced,which makes the shell fragile and easy to crack in the groove.?3?"Jinqiao 2" and "Xiaomiqiao" have different shell development patterns during seed development."Jinqiao2" is a bimodal type,that is,the content of cellulose and lignin increases rapidly at the young fruit stage?day 5?to reach the peak?day 10?,and then decreases in the following filling period?day 15?,And then increase to the peak again after entering the mature period?day 20?."Xiaomiqiao" shows an increasing single-peak mode that the cellulose and lignin content in the shell gradually accumulates till seed mature.?4?For the seed husks of four developmental stages of "Xiaomiqiao" and "Jinqiao 2"?5 days,10 days,15 days and 20 days after flowering,3 biological repeats for each period?,a total of 24 samples were subjected to high-throughput transcriptome sequencing,and the clean reads ranged from 41.4 × 106 to 44.9 × 106.Secondly,29,843 genes were identified in transcriptome sequencing,including 28,465 known genes and 1,378 new genes.Among all the samples,the low-and moderately-expressed genes accounted for the largest proportions,about 42% and 30%.?5?There were 4613,392,428 and 1216 stage specific / preferentially expressed genes identified in 4 periods of "Jinqiao 2",and 3959,267,413 and 1279 stage specific / preferentially expressed genes identified in 4 periods of "Xiaomiqiao".Through GO enrichment analysis,a large number of differential gene enrichment and cell cycle and cell growth were found on the 10 th day of husk development,indicating that the 10 th day of husk development is a critical period of cell wall biosynthesis.?6?A total of 9549 DEGs were identified in the four stages of husk development of "Xiaomiqiao" and "Jinqiao 2".1934,3916,1703 and 5884 DEGs were identified in "j₅-vs-x₅","j₁0-vs-x₁0","j₁5-vs-x₁5" and "j₂0-vs-x₂0",respectively.The DEGs were enriched in GO and KEGG.On the 10 th days,GO is enriched into processes related to cell wall formation include: phenylpropanoid biosynthetic process,cell wall organization or biogenesis,lignin biosynthetic process,phloem or xylem histogenesis and phloem development.The metabolic pathways found by KEGG enrichment includes: Phenylpropanoid biosynthesis,Plant hormone signal transduction,Starch and sucrose metabolism and Flavonoid biosynthesis.?7?On the 5th and 10 th day of the seed shell development of "Jinqiao 2" and "Xiaomiqiao",there are 8 key transcription factors related to secondary wall development,NST1,tow NST3 / SND1,ATMYB52,MBY52 / 54,MYB46 / 83,MYB103-1,MYB103-2,Respectively.Twenty key enzyme genes related to the formation of secondary cell walls were screened.Among them,there are three cellulose synthesis enzyme genes including AtCESA4,AtCESA7 and AtCESA8,eleven hemicellulose synthetase genes inluding CslC4,tow GXM,GUX4,IRX9,IRX14,TBL1,TBL3,TBL31,TBL33 and TBL34,and six lignin synthase genes including C4 H,tow CAD,CCR and tow CCoAOMT.?8?The 17 key transcription factors and enzyme genes related to the secondary wall of the cell were found.Using qRT-PCR to identify their relative expression levels in different developmental stages of "Jinqiao 2" and "Xiaomiqiao" husks?day 5,day 10,day 15 and day 20?,their results showed the R value about the two genes MYB83 and IRX9 was greater than 0.78 and the R values of the other genes were greater than 0.91.