Mapping and genomic targeting of the major leaf shape gene (L) in Upland cotton (Gossypium hirsutum L.)
A major leaf shape locus (L) was mapped with molecular markers and genomically targeted to a small region in the D-genome of cotton. By using expression analysis and candidate gene mapping, two LMI1 -like genes are identified as possible candidates for leaf shape trait in cotton.
Leaf shape in cotton is an important trait that influences yield, flowering rates, disease resistance, lint trash, and the efficacy of foliar chemical application. The leaves of okra leaf cotton display a significantly enhanced lobing pattern, as well as ectopic outgrowths along the lobe margins when compared with normal leaf cotton. These phenotypes are the hallmark characteristics of mutations in various known modifiers of leaf shape that culminate in the mis/over-expression of Class I KNOX genes. To better understand the molecular and genetic processes underlying leaf shape in cotton, a normal leaf accession (PI607650) was crossed to an okra leaf breeding line (NC05AZ21). An F2 population of 236 individuals confirmed the incompletely dominant single gene nature of the okra leaf shape trait in Gossypium hirsutum L. Molecular mapping with simple sequence repeat markers localized the leaf shape gene to 5.4 cM interval in the distal region of the short arm of chromosome 15. Orthologous mapping of the closely linked markers with the sequenced diploid D-genome (Gossypium raimondii) tentatively resolved the leaf shape locus to a small genomic region. RT-PCR-based expression analysis and candidate gene mapping indicated that the okra leaf shape gene (L o ) in cotton might be an upstream regulator of Class I KNOX genes. The linked molecular markers and delineated genomic region in the sequenced diploid D-genome will assist in the future high-resolution mapping and map-based cloning of the leaf shape gene in cotton.
KeywordsSimple Sequence Repeat Marker Leaf Shape Upland Cotton Normal Leaf Restriction Fragment Length Polymorphism Marker
We thank Cotton Incorporated for supporting this work through its core research and doctoral fellowship programs. We thank Kim Howell, Jared Smith, and Sharon Williamson at the USDA Eastern Regional Small Grains Genotyping Laboratory for assistance in capillary-based analysis of molecular markers. We also thank Rich Tuttle for supplying primers for GAPDH-positive control used in the expression analysis.
Conflict of interest
The authors declare that there are no conflicts of interest in the reported research.
The authors note that this research was performed and reported in accordance with ethical standards of the scientific conduct.
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