Fine Mapping And Cloning Of The Fuzzless Gene N₂ In Cotton

Cotton fiber,as a natural textile raw material,play an important role in national economy.High quality and high yield of cotton fiber is always the ultimate goal of cotton breeding.Cotton fibre are single cells derived from the ovule epidermis.Two types of cotton fiber,including lint and fuzz are developed from single epidermal cells of the seed.Therefore,cloning the fuzzless gene and studying its function laid a foundation for fibre formation mechanism.The cotton（Gossypium hirsutum L.）mutant n₂ is fuzzless gene,providing a crucial germplasm resource for cotton research.Two F₂ populations derived from a cross between the Xinhai21 and the mutant n₂ was constructed.Combined with cotton genomic data and developed SSR makers,compeleted the fiber character of individuals and genetic analysis,we finished the primary mapping and fine mapping.Then we predicted the candidate genes,and compeleted the cloning and expression analysis.Give the results as follows:（1）The cotton line Xinhai21 and a fuzzless mutant n₂ were employed to construct two F₂ segregating populations for preliminary mapping.The populations contains 3997 individuals.The fiber character of individuals were investigated and the F₂ population both contain fuzz and fuzzless.Chi-square analysis showed that the segregation ratio of F₂ populations were 3:1(χ²=0.59<χ²_0.05=3.84).（2）According to the previous work,n₂ was located in a 6 c M region on chromosome A12,between the marker of NAU943 and BNL1679.Based on the results and genome sequence,we developed new SSR markers,and a total of 10 molecular markers were used for fine mapping.Finally we narrowed down the candidate region to a 181 kb region,between the markers of P61 and Z10.（3）Predicted genes analysis in the region found that there were 7 candidate genes.q RT-PCR verification shows that there were significant differences in the expression of one candidate gene in two parents.This indicates showed that the expression may be caused the difference of the traits.We also constructed the virus-induced gene silencing（VIGS）vectors of this gene for functional verification of n₂ gene.