Submitted to: Biomed Central (BMC) Plant Biology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/5/2009
Publication Date: 1/2/2009
Citation: Taliercio, E.W., Romano, G.B., Scheffler, J.A., Ayre, B. 2009. Expression of genes associated with carbohydrate metabolism in cotton stems and roots. Biomed Central (BMC) Plant Biology. 9:11-17. Interpretive Summary: Cotton is unique among row crops because it is a perennial plant grown as an annual. Cotton stores reserves in the form of starch in its roots and stems. Starch levels peak about the time the plant starts to flower then the reserves are used to support seed and fiber development. Analysis of the expression of over 11,000 cotton genes using microarrays identified the pathways that result in the biosynthesis of starch prior to flowering and the mobilization of starch to developing seeds and fiber after flowering. These analyses also identified an increase in expression of genes associated with raffinose and trehalose metabolism. Analysis of carbohydrates in selected samples confirmed that raffinose levels increase as stems and roots age. These carbohydrates play an important role in development in other plant species.
Technical Abstract: 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. These reserves are not available to produce seed and fiber when cotton is grown as an annual crop. Analysis of developing cotton plants indicated that starch levels peaked about the time of first anthesis then began to decline. An earlier peak in levels of starch was occasionally observed and in some greenhouse-grown samples starch increased 2 week after first bloom. 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 carbohydrate metabolism, transcription activity and the proteasome. Genes associated with starch synthesis, starch degradation, sucrose metabolism, hexose metabolism, raffinose synthesis and trehalose synthesis increased in expression in starch accumulating tissues. The anticipated changes in these sugars were largely confirmed by measuring soluble sugars in relevant tissues. We propose that altering expressions of genes and pathways identified in this work could lead to a more efficient mobilization of stored carbohydrates for fiber production.