Abstract
Ligon lintless-2, a monogenic dominant cotton (Gossypium hirsutum L.) fiber mutation, causing extreme reduction in lint fiber length with no pleiotropic effects on vegetative growth, represents an excellent model system to study fiber elongation. A UDP-glycosyltransferase that was highly expressed in developing fibers of the mutant Ligon lintless-2 was isolated. The predicted amino acid sequence showed ~53% similarity with Arabidopsis UGT73C sub-family members and the UDP-glycosyltransferase was designated as UGT73C14. When expressed in Escherichia coli as a recombinant protein with a maltose binding protein tag, UGT73C14 displayed enzymatic activity toward ABA and utilized UDP-glucose and UDP-galactose as the sugar donors. The recombinant UGT73C14 converted natural occurring isoform (+)-cis, trans-ABA better than (+)-trans, trans-ABA and (-)-cis, trans-ABA. Transgenic Arabidopsis plants constitutively overexpressing UGT73C14 did not show phenotypic changes under standard growth conditions. However, the increased glycosylation of ABA resulted in phenotypic changes in post-germinative growth and seedling establishment, confirming in vivo activity of UGT73C14 for ABA. This suggests that the expression level of UGT73C14 is regulated by the observed elevated levels of ABA in developing fibers of the Li 2 mutant line and may be involved in the regulation of ABA homeostasis.
Highlights
Cotton is the major source of renewable fiber in the world, used primarily for a wide range of textile applications
The transcript abundance of this UDP glycosyltransferases (UGT) was significantly lower in fibers of the Li2 mutant compared to WT fibers during the elongation stage
The results indicate that UGT73C14 is present as a single copy per haploid genome – a total of 4 copies in the tetraploid hirsutum and 2 copies each in the diploid species G. arboreum, G. herbaceum, and G. raimondii
Summary
Cotton is the major source of renewable fiber in the world, used primarily for a wide range of textile applications. Genetic engineering has provided powerful tools for the improvement of cotton. The lack of information at the molecular level regarding genes and regulatory elements that control fiber development is one of the major limitations in the genetic improvement of cotton fiber. Cotton fiber mutants are valuable tools for understanding the biological processes of fiber development. In cotton several fiber-related mutants have been discovered, one of which is the monogenic and dominant Ligon lintless-2 (Li2), which exhibits an extreme reduction in the length of lint fiber [1]. Cytological studies have not revealed differences in seed fiber initiation between mutant and wild-type (WT) plants suggesting the effects of the mutation occurs later in development, likely during the elongation stage [2,3]. The Li2 mutant in a near-isogenic state with a wild-type represents a good model system to study fiber elongation
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