Analysis Of Dwarf Characteristics And Differentially Expressed Genes In Dwarf Mutant Of Tartary Buckwheat

Tartary buckwheat originated in the Nanlu area of the Himalayas in China.It is widely planted all over the world and has a long history of cultivation.The tartary buckwheat has high nutritional value,is rich in protein and flavonoids,has certain preventive and therapeutic effects on hypertension,diabetes and so on.It has the dual functions of nutrition health care and medicinal diet,and is a typical small and multi-grain crop for medicine and food.Tartary buckwheat has a high plant height,mostly 1.5~2 m,and the stem is hollow and easy to fall,which seriously affects the yield of tartary buckwheat and restricts the development of buckwheat industry.Therefore,breeding new varieties with ideal plant type and lodging resistance has become one of the currently urgent breeding targets.In this study,two dwarf mutants ftdm1 and ftdm2 of buckwheat obtained by the pre-EMS mutagenesis used as experimental materials.Through investigated their field traits,yield traits,stalk lodging resistance,and observed the microscopic structure of stem cells,and determined their rutin content of the grain would be clarified the phenotypic and quality differences between the wild type and the mutant.Meantime,the differentially expressed genes and transcript SNPs analysis were initially explored the molecular mechanism of dwarf formation from dwarf mutant in tartary buckwheat.The main results of this study were as follows:1.The dwarf phenotypes of the two dwarf mutants were approximately homozygous,up to 100% and92.31%,respectively;the plant heights of ftdm1 and ftdm2 were 82.48±1.98 and 79.5±10.18 cm,respectively,compared with the wild type 215.3±12.77 cm,reduced by 61.69% and 63.07%.The stalk thickness,100-grain weight and fresh(dry)weight of the mutant were higher than the wild type.The rutin content of ftdm2 grain was increased by 20.3% compared with wild type.The rutin content of ftdm1 grain was decreased by 19.4%.But the rutin content of other tissues of ftdm1 and ftdm2(leaf,stem and flower organ)were both lower than that of wild type.The leaves,stems and flower organs of ftdm1 were reduced by 22.10%,64.6% and 2.57%,respectively,compared with wild type.The tissues of ftdm2 were decreased by 21.57%,37.8% and 40.4%,respectively,compared with wild type.2.The flexural strength,compressive strength and tissue structural strength of ftdm1 dwarf mutant were significantly higher than those of wild type.However,the lodging index of ftdm1 was smaller than that of wild type,indicated that it was more resistant to lodging than wild type.Cytological observation showed that the length of the longitudinal section of the wild-type stem was 1.38 times that of ftdm1,and the cell width of the longitudinal section of the ftdm1 stem was increased by 39.3% compared with thewild type.The cell medullary cavity width and stem wall thickness of ftdm1 stalk cross section were 1.39 and 1.23 times of the wild type,respectively,and reached a significant level(p<0.05).3.The stem transcriptome analysis of ftdm1 and wild type showed that there were 8 776 significant differential genes,including 2 821 up-regulated genes and 5 955 down-regulated genes.All differentially expressed genes(DEGs)were annotated and classified into three major functional groups,including 42 functional categories,enriched to 1 898 GO terms.Meanwhile,all DEGs were mapped into 129 KEGG metabolic pathways,which were significantly enriched in phytohormone signal transduction and phenylpropanoid biosynthetic metabolic pathways,accounting for 8.67% and 5.27% of all genes.The DEGs contained 604 transcription factors classified into 47 transcription factor families.4.Through transcript SNPs analysis,functional annotation and expression analysis of genes with SNP mutations,finally 36 differentially expressed genes were identified,suggested that these genes were potential candidate genes associated with dwarf traits.According to these published report,10 candidate genes most likely related to dwarf traits were identified using q RT-PCR.The results showed that TTG1,Wdr70,ABCG21,UGT92A1,ZFP1 and ABC1 genes were up-regulated in ftdm1 stem tissue compared to wild type.The expression of WAT1,ARF4,CIPK14 and LAC17 genes were down-regulated in ftdm1 stem tissue.The correlation analysis with RNA-seq sequencing data and q RT-PCR values,the results showed that the correlation coefficient was 0.9399 as a linear correlation trend,indicated that the transcriptome analysis results were reliable.Subsequently,tissue specific expression was checked,the highest expression levels of TTG1,Wdr70,ABCG21,ABC1 and UGT92A1 genes were found in stem tissues.In summary,the growth and development morphology analysed,physiological and biochemical checked,DEGs and candidate genes prediction in dwarf mutants,it provides a good molecular basis for the subsequent in-depth study of the mechanism involved in plant hormone signal transduction and key metabolic pathways revealed on tartary buckwheat dwarfing.