| Potassium content is one of the important quality indicators of tobacco leaves,and the potassium content of tobacco leaves has obvious heterosis.It is of great significance to study the reasons for the formation of heterosis with potassium content in tobacco leaves for the breeding of hybrids with high potassium content.In this study,the hybrid combinations with large heterosis differences and their parents were used as materials to analyze the genetic characteristics of potassium content in tobacco leaves and the temporal and spatial changes of potassium content in tobacco leaves.Differentially expressed genes were obtained by genome sequencing technology,and functional annotation and enrichment analysis of the differentially expressed genes were performed by GO enrichment and KEGG analysis.The reasons for the formation of potassium content dominance in hybrid tobacco leaves,the research results can provide a theoretical basis for the breeding of high potassium content hybrids,and provide experimental examples for the research on the formation mechanism of crop heterosis.The main findings are as follows:1.The broad heritability of potassium content in tobacco leaves is 88.66% and the narrow heritability is 33.81%,indicating that the potassium content of tobacco leaves has high heritability and is less affected by the environment,and the variance of its special combining ability is higher than that of the general combining ability,indicating that the potassium content of tobacco leaves is higher than that of the general combining ability.The content is greatly affected by non-additive effects,and it is suitable for genetic improvement by using the method of heterosis utilization.K326,Va116 and GDH88 were excellent parents for improving potassium content of flue-cured tobacco leaves,and Va116×GDH88 was the hybrid combination with the highest potassium content.2.The potassium content of tobacco leaves of 6 parents and 9 hybrid combinations were measured 50 days,60 days,70 days,80 days and 90 days after transplanting,and the potassium content of tobacco leaves was screened during the key period of heterosis to determine The critical period for heterosis of potassium content in tobacco leaves was 70 days after transplanting.From 60 to 90 days after transplanting,the hybrid combinations with the highest positive heterosis value were all G70×GDH11(9.93%-46.46%),and the hybrid combination K326×GDH11 was a weaker hybrid from 50 to80 days after transplanting Dominance(-4.49%-3.75%).Therefore,the combination G70×GDH11 and K326×GDH11 with strong and weak potassium content in tobacco leaves were selected,and the formation mechanism of heterosis of potassium content in tobacco leaves was studied by transcriptome sequencing technology.3.The comparison results of RNA-Seq data of the hybrids and their parents showed that a total of 4663 differential genes were identified in the B1_vs_B3(G70_vs_G70×GDH11)comparison group,including 2879 down-regulated genes and1784 up-regulated genes;B2_vs_B3(GDH11_vs_G70×GDH11)A total of 4048 differential genes were identified in the comparison group,including 2417 downregulated genes and 1631 up-regulated genes.Weak dominant material A1_vs_A3(K326_vs_K326×GDH11)comparison group screened 2529 differential genes,of which 1148 genes were down-regulated and 1381 genes were up-regulated;A2_vs_A3(GDH11_vs_K326×GDH11)comparison group screened 377 differential genes,of which down-regulated expression There are 172 genes,and 205 are up-regulated.GO function enrichment analysis was performed on the differential genes,and the differentially expressed genes in different comparison groups were mainly enriched in three functions: biological process,cellular components and molecular functions.Among them,in biological processes,they are mainly concentrated in biological regulation,stimulation response and cellular processes;in cellular components,they are mainly concentrated in membrane part,organelle part and cell part;the largest proportion of molecular functions is transport activity,catalytic activity and binding capacity.KEGG functional annotation was performed on the differential genes,and the differentially expressed genes were mainly enriched in the phosphatidylinositol signaling system,phosphoinositide metabolism,plant hormone signal transduction,glycerophospholipid metabolism,photosynthesis and carotenoid biosynthesis.4.Among the strong and weakly dominant hybrids,the additive gene expression pattern accounted for 2.27% and 5.64% of the differentially expressed genes,and the non-additive gene expression pattern accounted for 97.73% and 94.36% of the differentially expressed genes,indicating that the potassium content of tobacco leaves heterosis It is greatly affected by non-additive effects,and the contribution of additive effects is smaller than that of non-additive effects.In addition,among the nonadditively expressed genes,the dominantly expressed genes accounted for 8.52% and37.91%,respectively,and the superdominantly expressed genes accounted for 89.21%and 56.45%,respectively.The genes were mainly up-regulated,and the over-dominant genes in the weakly dominant materials were mainly down-regulated.It indicated that the super-dominant expression of differential genes led to the generation of heterosis of potassium content in hybrid tobacco leaves.5.In the strong and weak dominant materials,145 differentially expressed genes were screened in common,among which: in the weak dominant material A3_VS_A1A2comparison group,there were 59 up-regulated differential genes and 86 down-regulated differential genes;In the material B3_VS_B1B2 comparison group,there were 77 upregulated differentially expressed genes and 68 down-regulated differentially expressed genes.Through further analysis of the common genes in the two groups of strong and weak dominant materials,it was found that 17 differentially expressed genes were down-regulated in the A3_VS_A1A2 comparison group and up-regulated in the B3_VS_B1B2 comparison group.The functions of these key genes are mainly lipid transport,binding and metabolism(Nitab4.5 0003963g0030,Nitab4.5 0001599g0040,Nitab4.5 0008221g0010),membrane composition(Nitab4.5 0008863g0010,Nitab4.50005620g0030),cell division(Nitab4.5 0000649g0180),plant organ morphogenesis(Nitab4.5 0000766g0090),ion binding(Nitab4.5 0004782g0030,Nitab4.50002635g0070),etc.;one differentially expressed gene was up-regulated in the A3_VS_A1A2 comparison group and was up-regulated in the B3_VS_B1B2comparison group The expression was down-regulated in the group,and its function was mainly in the aspect of nucleic acid binding(Nitab4.5 0004031g0010).To sum up,the potassium content of tobacco leaves has significant heterosis,which is involved in lipid transport,binding and metabolism(Nitab4.5 0003963g0030,Nitab4.5 0001599g0040,Nitab4.5 0008221g0010),membrane composition(Nitab4.50008863g0010,Nitab4.5 0005620g0030),cell division(Nitab4.5 0000649g0180)and other related genes were over-dominantly up-regulated,which may be the main reason for the formation of heterosis of potassium content in tobacco leaves. |
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