Title: A FIBERLESS SEED (FLS) MUTATION IN COTTON IS ASSOCIATED WITH LACK OF FIBER CELL INITIATION IN OVULE EPIDERMIS, LOSS OF SUCROSE SYNTHASE EXPRESSION ANDALTERED CARBON PARTITIONING IN DEVELOPING SEEDS.
Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 17, 1998
Publication Date: N/A
Interpretive Summary: In cotton, the most important textile fiber crop, the fiber originates from a single outermost seed coat cell in a developing seed. Overall, only 30% of the total seed coat cells initiate to become fibers. Thus, there is a large potential to increase fiber yields if we can increase the number of such cells which will become fiber cells. However, nothing is known about the developmental and/or metabolic basis of such modifications. To better understand this basic aspect of biology, we have analyzed a single gene mutation in cotton which yields no fibers (i.e., fiberless or a naked seed). The work reported here is done at the ARS, Crop Genetics & Environmental Research Unit, and University of Florida, Gainesville, FL, and is in part funded by a grant from U.S.- Israel Binational Agricultural Research & Development (BARD) Fund. The most significant findings are that the seed coat cells in the fiberless mutants are blocked in the very first developmental step where they 'initiate' to become a fiber cell. Further, the mutant shows several biochemical, molecular (gene expression) and metabolic changes that are associated with the blockage of fiber initiation. Collective data show, for the first time, that fiber initiation is a complex event controlled by a single master gene such as fiberless. Further molecular studies on such a gene would be highly rewarding to attain increase in cotton fiber yields
Fiber cell initiation from cotton ovule epidermis represents a unique example of trichome development in higher plants. Little is known about the molecular and metabolic mechanisms controlling this process. We report here a comparative analysis of the normal (FLS) and a fiberless seed (fls) mutant (lacking fibers) to better understand the initial cytological events in fiber development, and to analyze metabolic changes that are associated with the loss of a major sink for sucrose utilization in cellulose biosynthesis in the mutant seeds. At the cellular level, unlike the FLS ovules, the mutant ovular epidermal cells, on the day of anthesis (0 DAA), lacked the typical bud-like projections required for commitment to the fiber development pathway. The mutant cells also lacked sucrose synthase (SuSy) RNA and protein coincident with the stage of fiber initiation. Tissue level analyses of developing seeds, 15 35 DAA, have shown an altered temporal pattern of SuSy expression in the mutant relative to the normal genotype. Whether the altered programming of SuSy expression is the causal or the resultant effect of the mutation is unknown. The developing seeds of the fls mutant have also shown several correlated changes that represent altered carbon partitioning in seed coats and cotyledons as compared to the FLS genotype.