The Short Fiber Mutation Is Located Within a Terminal Deletion of Chromosome 18 in Cotton

Extreme elongation distinguishes about one-fourth of cotton ( sp.) seed epidermal cells as "lint" fibers, useful for the textile industry, from "fuzz" fibers (<5 mm). ( ), a dominant mutation that results in no lint fiber but normal fuzz fiber, offers insight into pathways and mechanisms that differentiate spinnable cotton from its progenitors. A genetic map developed using 1,545 F2 plants showed that marker CISP15 was 0.4 cM from , and "dominant" simple sequence repeat (SSR) markers (i.e. with null alleles in the genotype) SSR7 and SSR18 showed complete linkage with Nonrandom distribution of markers with null alleles suggests that the phenotype results from a 176- to 221-kb deletion of the terminal region of chromosome 18 that may have been masked in prior pooled-sample mapping strategies. The deletion includes 10 genes with putative roles in fiber development. Two Glycosyltransferase Family 1 genes showed striking expression differences during elongation of wild-type versus fiber, and virus-induced silencing of these genes in the wild type induced like phenotypes. Further, at least 7 of the 10 putative fiber development genes in the deletion region showed higher expression in the wild type than in mutants during fiber development stages, suggesting coordinated regulation of processes in cell wall development and cell elongation, consistent with the hypothesis that some fiber-related quantitative trait loci comprise closely spaced groups of functionally diverse but coordinately regulated genes.