In situ analysis of cotton fibre cell wall polysaccharides

The cotton fibre is one of the most economically important cells in the world. Each year, over 25 million tonnes are harvested and the industry is responsible for 300 million jobs world-wide, with revenues of over $120 billion in the USA alone. For such an important cell there is little known about its cell wall composition as well as the functional roles of these polysaccharides during fibre development. Although much work has already been done on the cotton fibre transcriptome, a study of cell wall composition during development and maturation is crucial in linking these data to further understand fibre differentiation. This research explored the developmental biology of the cotton fibre in relation to key polysaccharide structures and architectural properties in the context of cell wall development. This has been achieved by the development of methodologies for the detection and imaging of low level polysaccharide epitopes of the cotton fibre using molecular probes known as monoclonal antibodies (mABs) and carbohydrate-binding modules (CBMs), directed in-situ to these glycans. Key polysaccharide changes were observed during fibre development, maturity and processing. Upon maturity, pectic homogalacturonan and xyloglucan were readily detectable at the surface of fibres after removal of the waxy outer layer. Other polysaccharides including arabinan, xylan and mannan, as well as cell wall glycoproteins were detected after treatments that removed the pectin-rich primary cell wall layer. This research shows that cell wall probes are powerful and useful tools to study cotton fibres throughout development, maturity and processing in the context of cell wall biology, though these polysaccharide changes need to be explored one by one to establish structure-function relationships. With the upcoming sequencing of the G. hirsutum genome, cotton fibre research will be an exciting field and the work presented here will provide a base for future studies, with potential for the manipulation of key developmental polysaccharides to alter the final fibre properties. The ultimate goal of improving cotton fibre properties will have significant economic, ecological and societal impacts for decades to come.