Transcriptome Analysis And Key Genes Screening Of Sucrose- Induced Tuberization On Potato (Solanum Tuberosum L.)

Potato(Solanum tuberosum L.)is one of the four major food crops in the world and has played increasingly important role in the national food security along with the launch of staple food strategy.Potato tubers are both edible organs and reproductive organs,which directly affect the yield and quality of potato as the reproductive organs.Because the viral degeneration of asexual reproduction is the key factors to the quality of seed potato,the research on the production technology of virus-free seed potato has been an important field of seed potato breeding.Potato microtubers are formed by virus-free seedlings in the culture box,not only without virus and without any pathogens,so,the application of potato microtubers has become the hotspot of seed potato production technology in recent years.Our laboratory has been committed to the development mechanism and application research of potato microtubers.In our previous work,although a number of QTLs affecting tuber formation had been mapped and the molecular mechanism by which light quality and photoperiod regulate tuberization had been investigated,other factors such as concentration of sucrose should not be ignored when tubers are formed in vitro.This project was aim to search for candidate genes assotiated with the sucrose concentration,which affect the formation of potato microtubers in vito,by analyzing transcriptome profiles.The results will lay a promising foundation for the study of regulatory network of potato tuberization.The main results of the project are as follows:1.Phenotypic evaluation of three potato genotypes under different sucrose concentrations treatments.Three sister lines E20,E26 and E109,which were derived from same cross,were cultured in different sucrose concentrations(high sucrose concentration: 8%,10% and low sucrose concentration: 2%,4%)to test the formation of potato microtubers.We found that in low sucrose concentrations with 2% or 4%,all three lines could not form microtubes,whereas in high concentrations with 8% or 10% of sucrose,E26 and E109 could formed tubers while E20 did not.The results indicated that high concentration of sucrose was essential for the formation of potato microtubers but was genotype-dependent.2.For obtaining the potential sucrose-induced potato microtuber formation related genes,a sucrose-sensitive line-E26,was treated with different conditions for transcriptomic study: cultured in 10%(high concentration)or 2%(low concentration)sucrose,harvested after 0,2 or 5 days of culture.After the RNA sequencing,around 1.2×107 clean reads were obtained for each sample,which account for more than 98.3% of raw reads in each as well.The preliminary bioinformatics analysis showed 1194 genes were differentially expressed upon sucrose treatment.3.The differentially expression genes(DEGs)were analyzed by gene ontology(GO)and KEGG pathways.There were 683 genes which were functionally annotated with GO among the 1194 DEGs,which also were involved in 138 biological processes.Meanwhile,550 genes,which related to 106 metabolic pathways,were highlighted from KEGG analysis.These results indicated that sucrose-induced formation of potato microtuber were regulated by a variety of metabolic pathways.4.In total,118 DEGs from transcriptomic analysis were taken for verification.The transcriptomic data were significantly(R=0.742**)correlated with q-PCR data.According to the expression rate changes,6 candidate genes were selected with strong response to high concentration sucrose,namely they were PGSC0003 DMG 400004800,PGSC0003DMG400018398,PGSC0003DMG400018399,PGSC0003 DMG400018401,PGSC0003DMG400022750,PGSC0003DMG400027338.Additionally,another 15 differentially expressed genes were identified within QTL MT05 region through our previews work.These 21 candidate genes might play important roles in the sucrose-induced potato tuberization.It has been proved that high concentration of sucrose was essential for the formation of potato microtubers.The candidate genes obtained through this study could shed light on the molecular mechanisms underlying the complex regulatory networks of potato tuber formation.