Role of xyloglucan in cotton (Gossypium hirsutum L.) fiber elongation of the short fiber mutant Ligon lintless-2 (Li-2)

摘要

Xyloglucan is a matrix polysaccharide found in the cell walls of all land plants. In growing cells, xyloglucan is thought to connect cellulose microfibrils and regulate their separation during wall extension. Ligon lintless-2 (Li-2) is a monogenic dominant cotton fiber mutation that causes extreme reduction in lint fiber length with no pleiotropic effects on vegetative growth. Li-2 represents an excellent model system to study fiber elongation. To understand the role of xyloglucan in cotton fiber elongation we used the short fiber mutant Li-2 and its near isogenic wild type for analysis of xyloglucan content and expression of xyloglucan-related genes in developing fibers. Accumulation of xyloglucan was significantly higher in Li-2 developing fibers than in wild type. Genes encoding enzymes for nine family members of xyloglucan biosynthesis were identified in the draft Gossypium hirsutum genome. RNAseq analysis revealed that most differentially expressed xyloglucan-related genes were down-regulated in Li-2 fiber cells. RT-qPCR analysis revealed that the peak of expression for the majority of xyloglucan-related genes in wild type developing fibers was 5-16 days post anthesis (DPA) compared to 1-3 DPA in Li-2 fibers. Thus, our results suggest that early activation of xyloglucan-related genes and down regulation of xyloglucan degradation genes during the elongation phase lead to elevated accumulation of xyloglucan that restricts elongation of fiber cells in Li-2.