Research article

Expression of genes associated with carbohydrate metabolism in cotton stems and roots

Earl W Taliercio¹ , Gabriela Romano² , Jodi Scheffler² and Brian G Ayre³

¹USDA/ARS, 3127 Ligon St., Raleigh, North Carolina 27695, USA

²USDA/ARS, 141 Experiment Station Road, Stoneville, Mississippi 38776, USA

³University of North Texas, Department of Biological Sciences, 1504 W. Mulberry, SRB Rm 120, P.O. Box 305220, Denton, TX 76203 5220, USA

author email corresponding author email

BMC Plant Biology 2009, 9:11doi:10.1186/1471-2229-9-11

Published:	22 January 2009

Abstract

Background

Cotton (Gossypium hirsutum L) is an important crop worldwide that provides fiber for the textile industry. Cotton is a perennial plant that stores starch in stems and roots to provide carbohydrates for growth in subsequent seasons. Domesticated cotton makes these reserves available to developing seeds which impacts seed yield. The goals of these analyses were to identify genes and physiological pathways that establish cotton stems and roots as physiological sinks and investigate the role these pathways play in cotton development during seed set.

Results

Analysis of field-grown cotton plants indicated that starch levels peaked about the time of first anthesis and then declined similar to reports in greenhouse-grown cotton plants. Starch accumulated along the length of the stem and the shape and size of the starch grains from stems were easily distinguished from transient starch. Microarray analyses compared gene expression in tissues containing low levels of starch with tissues rapidly accumulating starch. Statistical analysis of differentially expressed genes indicated increased expression among genes associated with starch synthesis, starch degradation, hexose metabolism, raffinose synthesis and trehalose synthesis. The anticipated changes in these sugars were largely confirmed by measuring soluble sugars in selected tissues.

Conclusion

In domesticated cotton starch stored prior to flowering was available to support seed production. Starch accumulation observed in young field-grown plants was not observed in greenhouse grown plants. A suite of genes associated with starch biosynthesis was identified. The pathway for starch utilization after flowering was associated with an increase in expression of a glucan water dikinase gene as has been implicated in utilization of transient starch. Changes in raffinose levels and levels of expression of genes controlling trehalose and raffinose biosynthesis were also observed in vegetative cotton tissues as plants age.