Genetic Analysis And Mapping Of Genes Controlling Lettuce Lobed Leaf And Stem Spine

Lettuce?Lactuca sativa?is one of the most important vegetables worldwide.Lettuce cultivars have different morphological characteristics.Compared with wild lettuces,cultivated lettuce has dramatically different phenotypes,including leaf shapes and stem spines.However,the molecular basis for such variations remains unknown.In this study,F₂ segregating populations were used to map genes controlling lobed leaf and stem spine.The results are as follows:1.Research on lobed leaf traits:A F₂ population derived from a cross between lettuce PI491070?non-lobed leaf?×PI536760?lobed leaf?was used to study leaf shapes.Two pools,one for lobed leaf?30individuals?and one for non-lobed leaf,were made.Total RNAs were extracted from the two pools and sent to company for sequencing.The frequency of the two alleles of each SNP in two pools was calculated and the allele difference was plotted along lettuce chromosomes.Using BSR-Seq,the plot clearly showed that the gene controlling lobed leaf was located on Chr3,in the interval of 90Mb-140 Mb.A large F₂ population with4000 indiviuals was used to fine map the causual gene to the interval of Chr3:116.24Mb-118.15 Mb.Twenty-four genes were predicted in this region.One gene LG3316063,which encoded zinc finger protein,is only one base pair difference between two parents,and the base pair difference causes different amino acid.It is show similar changes between genotype and phenotype in the 12 indiviuals.We deduced that the gene LG3316063 is considered as the candidate gene controlling the lettuce lobed leaf.2.Genetic analysis of lettuce stem spine:The spines in the stems of wild lettuce are consisted of multicellular trichomes.Similar approach was used to study this trait.First,plants W111?non-stem spine?and PI491245?stem spine?was crossed and the F1 plants were selfed to generate the segregating F₂ population.Two extrem pools were made,one for 30 individuals with spine and one for 30 individuals without spine.RNA was extracted and sent to sequence.We primarily mapped gene on chromosome 5,in the interval of 304.36Mb-311.96 Mb.Using a F₂ population of 3500 individuals,the gene was fine maped to Chr5:306.31Mb-307.31 Mb.In this region,gene LG5467628 was differentially expressed between spine and non-spine genotypes,and this gene is considered as the candidate gene controlling stem spine in lettuce.