Analysis Of The Regulation Mechanism Of Yield And Harvest Index In Brassica Napus Based On Multi-omics

Rapeseed(Brassica napus L.)is the largest oilseed crop in China,which main producing area in the Yangtze River basin accounts for more than 85%of the cultivated area in China.Different from rice and wheat crops,the biological yield of it has more influence on the economic yield than the harvest index.It needs to be further studied how high the biological yield of rapeseed is suitable for the harvest index and the economic yield of the population.Therefore,the research on the yield and harvest index of Brassica napus is of great significance for rapeseed breeding.In this study,the yield and harvest index extreme phenotypic materials harvested in the spring of 2016 in Xiema,Chongqing and Lincang,Yunnan were used(included high harvest material SWU47 and low harvest index material ningyou 12).The green pod stage was taked to pick the main stem of plant,the pericarp and seeds from main inflorescence and the lateral branch.Transcriptome sequencing,miRNA sequencing,and whole genome bisulfite sequencing were performed using high-throughput sequencing technology.And the co-expression network was carried out.1.Transcriptome analysis of yield and harvest index of B.napusFinally,1222 DEGs with different intersection were obtained in Chongqing and Yunnan.The GO analysis revealed that DEGs were mainly enriched in amino acid synthesis,methylation,phosphorylation and other epigenetic modifications,which indicate epigenetic modification may plays a key role in the regulation of harvest index.In addition,auxin response factor ARF2 and stress response factor A TAF2 were found in DEGs.The up regulation of ARF2 can lead to the decrease of seed size and oil content of Arabidopsis.ATAF2 can improve the tolerance of plants to stress by inhibiting the catabolism of brassinosteroids.This two genes showes extreme expression.Therefore,this study speculated that ARF2 and ATAF2 may increase the oil content and seed size,as well as the tolerance degree of the plants to external stress,and enhance the adaptability of the plants to the environment,so as to further increase the yield and affect the harvest index of B.napus.2.MicroRNA analysis of yield and harvest index of B.napusTo explore the upstream regulation of genes,high-throughput sequencing was used to detect DEmiRNA between the five tissue sites of the extreme phenotype materials planted in Chongqing and Yunnan based on transcriptome sequencing results.A total of 959 miRNAs were identified,including 910 new miRNAs.250 of them were differently expressed in Chongqing while 219 were differently expressed in Yunnan.GO analysis of target genes reveals that miRNA could regulate genes by participating in the epigenetic modification pathway.In addition,the result shows that miRNA172 was highly expressed in all the main stem materials,suggesting that miRNA172 had tissue expression preference.3.Whole genome bisulfite sequencing analysis of high and low harvest index of B.napusWhole genome bisulfite sequencing analysis result shows the methylation level of C genome was significantly higher than A genome,which states that the methylation patterns between Brassica rapa and Brassica oleracea can be stably inherited to B.napus.The results of DMR analysis showed that there was a large amount of DMR in the promoter region.After annotation of DMR and co-analysis with DEG and DEmiRNA,44 DEGs were found with methylation regulation in promoter region,7 of them also have relationship with DEmiRNA which speculated that these miRNAs,together with methylation,regulate the expression of target genes.4.Construction of co-expression network of yield and harvest index of B.napusThe co-expression network of genes was constructed with the combination of three methylation degree data.Finally,30 gene modules whose expression patterns were significantly correlated with the methylation degree were obtained.The primary network of BBM and MYB118 were also construct which negatively correlated with methylation.We also got the target genes such as ABI3,TCX2 and AFO,which have same positive expression pattern of BBM,and MYB56 and MYB110 whose expression pattern is same with MYB118.The results revealed the effect of methylation on gene expression in plants from another point of view,which laid a theoretical foundation for the study of the yield and harvest index of B.napus.