Functional Characterization Of SlSD1 Involved In Stem Development In Tomato

As a vegetable crop,tomato is widely grown in China.Tomato stem affects plant growth and development,mineral elements absorption and transportation,yield formation and lodging resistance.In this study,a genome-wide association study about stem diameter based on 5.5 M SNPs obtained from 360 diverse accessions re-sequencing was performed and we found a gene named SlSD1 on chromosome 9.Transgenic have done to identify the function of SlSD1 and it can regulate the tomato stem diameter.We do preliminary study of its function and current research results obtained are as follows:1.Through the analysis of the data of the 275 core accessions in the 360 re sequencing materials based on the evolution of tomato,we found that the evolution of tomato stem is from thin to thick.2.There is a 11 bp deletion in the SlSD1 upstream of the initiation codon 1824 bp in thick materials,which led to more than three cis elements in thick materials promoter,and there is a 82 bp deletion in thick stem materials at first intron.5 SNPs of 12 SNPs in SlSD1 lead to amino acid change.To analyse the distribution of the Lead SNP in three groups,the result show that the Lead SNP is artificial selected and the SlSD1 is in domestication area.3.To analyse the genotypes of the 360 re-sequencing materials combined with the SNPs and indel,the main genotype isΔ^{11 bp}Δ^{82 bp}AGCTG in thick materials,but there are two genotypes,+^{11 bp}+^{82 bp}GTGCA andΔ^{11 bp}Δ^{82 bp}AGCTG in thin materials.The genotype of SlSD1 in some thin materials isΔ^{11 bp}Δ^{82 bp}AGCTG,on the one hand,other SNPs in SlSD1 may cause stem to thin;on the other hand,the stem diameter is a quantitative characters,so it must be regulated by other genes at the same time.4.In the SlSD1 transgenic plants,the OE plants stem are significantly thicker,and the fruits are bigger than wild types,at the same time OE plants are growing stronger than wild types.The RNAi plants stem are significantly thinner,and the fruits are smaller than AC,but there is no significant difference between them in the growth.5.By observing the paraffin section of tomato stem,the transgenic plants and the background materials were mainly different in secondary phloem cell.The secondary phloem cell is smaller and layers is less than wild type in RNAi plants.But only the secondary phloem cell is bigger than AC in OE plants,and the secondary phloem cell layers isn‘t changed.6.By detecting the expression level of SlSD1 in the thick and thin materials,we found that the expression was high in young tissues such as the stem apex,flower buds,young leaves and young fruits,and the expression level was lower in mature stems and roots.At the same time,we detected the expression of SlSD1 in the extreme material of the GWAS natural population,and found that there was no significant correlation between the SlSD1 expression level and stem thickness.7.Because the c DNA of SlSD1 is too long,it was divided into 3 fragments.We chose SlSD1-A and SlSD1-B to do yeast two hybrid,but there was no gene interacting with them.We also did yeast one hybrid by the 11 bp deletion,yet for verification.