Submitted to: Journal of Cotton Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 27, 2004
Publication Date: July 15, 2004
Citation: Taliercio, E.W., Kloth, R.H. 2004. Expression and characterization of a UDP-glucose pyrophosphorylase gene in cotton. Journal of Cotton Science. 8:91-98. Interpretive Summary: The genetics and physiology of cotton fiber development in general, and cellulose synthesis in particular, are largely unknown. This lack of information retards the development of high yielding varieties with fiber of superior quality. Mature cotton fibers are nearly pure cellulose. The basic building block of cellulose is a modified sugar, UDP-glucose (UDPG). Two enzymes synthesize UDPG: sucrose synthase and UDP-glucose pyrophosphorylase (UDPGpase). We studied the expression of UDPGpase and found that the gene was expressed at higher levels when cellulose was synthesized in large amounts by the fiber. We also found that this gene was not exclusively expressed in the fiber, but could also be found in seedlings and the cottonseed. We examined the part of the UDPGpase gene that determines in what part of the plant the gene will be expressed. We found sequences that are associated with gene expression in seedlings and seed - the same tissues where we observed UDPGpase expression. The data taken as a whole indicates that UDPGpase may play a role in providing UDPG for the developing cellulose chain. However, UDPG is an important compound in plant metabolism and so UDPGpase may be playing a role in these reactions.
Technical Abstract: UDP-glucose pyrophosphorylase (UDPGp) along with Sucrose synthase (Susy) is a source of UDP-glucose in cotton fiber. Susy plays an important role in cellulose metabolism during rapid secondary cell wall biogenesis by providing UDP-glucose directly to cellulose synthase. The role of UDPGp is unclear but an increase in UDPGp activity has been observed while cotton fiber is synthesizing massive amounts of cellulose. We have determined that cotton fibers, seeds and leaves express the same UDPGp gene at various stages of development and that there is an increase in the steady state level of UDPGp mRNA correlated with cellulose biosynthesis in fiber. The 5' end of a UDPGp gene expressed in fiber was isolated and the organization determined. Motifs potentially important in controlling gene expression were also identified.