In silico and functional characterization of the promoter of a Eucalyptussecondary cell wall associated cellulose synthase gene (EgCesA1)

Abstract

Background Cellulose is an important biopolymer produced by all plants and is used in a number of different industries, including for pulp and paper production. Cellulose is deposited into the plant cell wall by a large membranebound protein complex, which is composed of different cellulose synthase (CESA) proteins. The cellulose content and pattern of deposition in plant cell walls is highly variable depending on the function of the cell. All plant cells have a thin primary cell wall, but a number of plant cell types, including xylem cells, also deposit a secondary cell wall to give these tissues mechanical strength required to perform their function. Different cellulose synthase (CesA) genes have been shown to be involved in the deposition of primary and secondary walls. In Arabidopsis, three CesA (AtCesA4, 7 and 8) genes have consistently been associated with cells depositing secondary cell walls, while a different set of CesA genes have been shown to function during primary cell wall formation [Reviewed in 1]. These findings have been mirrored by studies of CesA gene orthologs in Populus and Eucalyptus[2-4]. While there have been a number of studies on CesA genes and their functions, much less is known about the regulation of these genes. In a previous study, we investigated the promoters of CesA genes involved in primary and secondary cell wall formation by performing a phylogenetic footprinting analysis to identify cis-elements conserved in the promoters from orthologous Arabidopsis, Populus and Eucalyptus cellulose synthase genes [5]. We identified a number of putative cis-regulatory elements that may play a role in the regulation of cellulose biosynthesis during primary and secondary cell wall formation. In the current study our aim is to further validate the ciselements identified in the CesA gene promoters by investigating their conservation across different Eucalyptus species and to determine the regulatory function of these promoter regions and the proteins which bind to them.