|SONG, XIANLIANG - Shandong Agricultural University|
|Delhom, Christopher - Chris|
Submitted to: G3, Genes/Genomes/Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/24/2016
Publication Date: 6/1/2016
Citation: Thyssen, G.N., Fang, D.D., Zeng, L., Song, X., Delhom, C.D., Condon, T.L., Li, P., Kim, H.J. 2016. The immature fiber mutant phenotype of cotton (Gossypium hirsutum) is linked to a 22-bp frame-shift deletion in a mitochondria targeted pentatricopeptide repeat gene. G3, Genes/Genomes/Genetics. 6:1627-1633.
Interpretive Summary: Cotton fiber thickness which is a combination of fiber maturity and fineness is an important physical property determining quality of fibers and textiles. However, it has not been characterized which gene is responsible for determining the degree of cotton fiber cell wall thickness. By comparing genome sequences of the immature fiber mutant producing immature and thin fibers with its isogenic wild type cotton producing mature and thick fibers, we identified that a mutation of pentatricopeptide repeat (PPR) impeded mitochondrial biological processes in the immature fiber mutant from generating mature fibers. The discovery provides insight how fiber thickness is regulated during cotton fiber development and allows cotton breeders to better understand and improve the fineness and maturity of cotton fibers, and therefore cotton textiles.
Technical Abstract: Cotton seed trichomes are the globally most important source of natural fibers. The major fiber thickness properties influence the price of the raw material and the quality of the finished product. The recessive immature fiber (im) gene reduces the degree of fiber cell wall thickening by a process that was previously shown to involve mitochondrial function in allotetraploid Gossypium hirsutum. Here we present the fine genetic mapping of the im locus, gene expression analysis of annotated proteins near the locus and association analysis of the linked markers. Mapping-by-sequencing identified a 22-bp deletion in a pentatricopeptide repeat (PPR) gene that is completely linked to the immature fiber phenotype in 2,837 F2 plants and is absent from all 163 cultivated varieties tested, although other closely linked marker polymorphisms are prevalent in the diversity panel. This frame-shift mutation results in a transcript with two long open reading frames: one containing the N-terminal transit peptide that targets mitochondria, the other containing only the RNA-binding PPR domains, suggesting that a functional PPR protein cannot be targeted to mitochondria in the im mutant. Taken together, these results suggest that PPR gene Gh_A03G0489 is involved in the cotton fiber wall thickening process and is a promising candidate gene at the im locus. Our findings expand our understanding of the molecular mechanisms that modulate cotton fiber fineness and maturity, and may facilitate the development of cotton varieties with superior fiber attributes.