Abstract
BackgroundCotton fiber length is a key determinant of fiber quality for the textile industry. Understanding the molecular basis of fiber elongation would provide a means for improvement of fiber length. Ligon lintless-1 (Li1) and Ligon lintless-2 (Li2) are monogenic and dominant mutations, that result in an extreme reduction in the length of lint fiber to approximately 6 mm on mature seeds. In a near-isogenic state with wild type (WT) cotton these two short fiber mutants provide an excellent model system to study mechanisms of fiber elongation.ResultsWe used next generation sequencing (RNA-seq) to identify common fiber elongation related genes in developing fibers of Li1 and Li2 mutants growing in the field and a greenhouse. We found a large number of differentially expressed genes common to both mutants, including 531 up-regulated genes and 652 down-regulated genes. Major intrinsic proteins or aquaporins were one of the most significantly over-represented gene families among common down-regulated genes in Li1 and Li2 fibers. The members of three subfamilies of aquaporins, including plasma membrane intrinsic proteins, tonoplast intrinsic proteins and NOD26-like intrinsic proteins were down-regulated in short fiber mutants. The osmotic concentration and the concentrations of soluble sugars were lower in fiber cells of both short fiber mutants than in WT, whereas the concentrations of K+ and malic acid were significantly higher in mutants during rapid cell elongation.ConclusionsWe found that the aquaporins were the most down-regulated gene family in both short fiber mutants. The osmolality and concentrations of soluble sugars were less in saps of Li1 – Li2, whereas the concentrations of malic acid, K+ and other detected ions were significantly higher in saps of mutants than in WT. These results suggest that higher accumulation of ions in fiber cells, reduced osmotic pressure and low expression of aquaporins, may contribute to the cessation of fiber elongation in Li1 and Li2 short-fiber mutants. The research presented here provides new insights into osmoregulation of short fiber mutants and the role of aquaporins in cotton fiber elongation.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0454-0) contains supplementary material, which is available to authorized users.
Highlights
IntroductionUnderstanding the molecular basis of fiber elongation would provide a means for improvement of fiber length
Cotton fiber length is a key determinant of fiber quality for the textile industry
Sources of variability in Results: We used next generation sequencing (RNA-seq) data We examined genome-wide gene expression in elongating cotton fiber cells at 8 Day post-anthesis (DPA) in Li1, Li2 mutants and wild type (WT) under different growing conditions, in the field and greenhouse
Summary
Understanding the molecular basis of fiber elongation would provide a means for improvement of fiber length. Apart from its economic importance, the cotton fiber provides a unique single-celled model system to study cell elongation and cell wall biogenesis in the absence of cell division [1]. Fiber elongation starts on the day of anthesis and continues for about 3 weeks before the cells switch to intensive secondary cell wall cellulose synthesis. The fiber cells elongate up to 3000 fold during 3 weeks which makes them the fastest growing and longest single cell known in higher plants [4]. Understanding the molecular basis of Naoumkina et al BMC Plant Biology (2015) 15:65 fiber elongation would provide a means for cotton breeders and researchers to improve the fiber length while maintaining yield and other cotton characteristics
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