Designer Fibres: Manipulating the chemical composition of cotton fibre cell walls to produce fibres with novel properties

Project Leader: Filomena Pettolino

Key Researchers: Filomena Pettolino, Colleen MacMillan, Vivien Rolland, Stuart Gordon

Brief Summary of Project Objectives:
The aim of this project is to modify cotton fibre properties, primarily elongation and strength, by targeting specific polysaccharide and protein components of the cotton fibre cell wall, namely callose and AGPs.  

Executive Summary

Key highlights of the last year’s research have been

  • Constructs to silence and over-express the most highly expressed callose synthase genes in cotton have been designed and we have tested two of the over-expression construct in a transient leaf expression system.
  • Transgenic cotton at T1 stage for the RNAi silencing and two sets of over-expression lines for GhFLA was grown and gene expression and Cottonscope analysis completed. Seed from these lines were collected and sown for experiments with the T2 generation but we did not have enough fibre for HVI to test strength and elongation properties.   
  • Transgenic lines for FLA promoter analysis to identify where it is expressed in Arabidopsis is underway with results indicating it is expressed in trichomes, root tips, lateral root emergence sites and root vascular tissue. The cotton  promoter-GUS transgenic lines have suffered delays due to the hailstorm, but we have managed to rescue some lines to proceed with their analysis. 
  • Other domains of the GhFLA protein have been tested to confirm their functionality. Our data shows that the signal peptide directs the protein through the ER and out to the cell wall/apoplast, that the putative GPI anchor site is processed as expected for a GPI anchor site and allows the protein to be both plasma membrane bound and unbound in the apoplast.
  • BEACH/Spi silencing lines of G. hirsutum to confirm the identity of the mutated gene responsible for the short fibre, distorted trichome phenotype observed in the original 110505 mutant identified in G. arboreum were tested for mature fibre quality properties. These lines generally show a shorter mature fibre length phenotype consistent with the role of the gene in determining fibre length.