Abstract
BackgroundThe cellulose synthase and cellulose synthase-like gene superfamily (CESA/CSL) is proposed to encode enzymes for cellulose and non-cellulosic matrix polysaccharide synthesis in plants. Although the rice (Oryza sativa L.) genome has been sequenced for a few years, the global expression profiling patterns and functions of the OsCESA/CSL superfamily remain largely unknown.ResultsA total of 45 identified members of OsCESA/CSL were classified into two clusters based on phylogeny and motif constitution. Duplication events contributed largely to the expansion of this superfamily, with Cluster I and II mainly attributed to tandem and segmental duplication, respectively. With microarray data of 33 tissue samples covering the entire life cycle of rice, fairly high OsCESA gene expression and rather variable OsCSL expression were observed. While some members from each CSL family (A1, C9, D2, E1, F6 and H1) were expressed in all tissues examined, many of OsCSL genes were expressed in specific tissues (stamen and radicles). The expression pattern of OsCESA/CSL and OsBC1L which extensively co-expressed with OsCESA/CSL can be divided into three major groups with ten subgroups, each showing a distinct co-expression in tissues representing typically distinct cell wall constitutions. In particular, OsCESA1, -3 & -8 and OsCESA4, -7 & -9 were strongly co-expressed in tissues typical of primary and secondary cell walls, suggesting that they form as a cellulose synthase complex; these results are similar to the findings in Arabidopsis. OsCESA5/OsCESA6 is likely partially redundant with OsCESA3 for OsCESA complex organization in the specific tissues (plumule and radicle). Moreover, the phylogenetic comparison in rice, Arabidopsis and other species can provide clues for the prediction of orthologous gene expression patterns.ConclusionsThe study characterized the CESA/CSL of rice using an integrated approach comprised of phylogeny, transcriptional profiling and co-expression analyses. These investigations revealed very useful clues on the major roles of CESA/CSL, their potentially functional complement and their associations for appropriate cell wall synthesis in higher plants.
Highlights
The cellulose synthase and cellulose synthase-like gene superfamily (CESA/CSL) is proposed to encode enzymes for cellulose and non-cellulosic matrix polysaccharide synthesis in plants
The CSLC family contains a glucan synthase involved in the synthesis of the backbone of xyloglucan [22,23], and several CSLD mutants have been characterized for their potential roles in wall polysaccharide synthesis [24,25,26,27]
We performed a validated approach that is applicable in higher plants and successful at finding out useful clues on OsCESA/CSL protein interaction or association
Summary
The cellulose synthase and cellulose synthase-like gene superfamily (CESA/CSL) is proposed to encode enzymes for cellulose and non-cellulosic matrix polysaccharide synthesis in plants. In Arabidopsis and guar, genes of the CSLA family are demonstrated to encode (1,4)-b-D-mannan synthases [16,17,18,19]; in rice, genes of the CSLF family have been implicated in the biosynthesis of (1,3;1,4)-b-D-glucans [20]. The CSLC family contains a glucan synthase involved in the synthesis of the backbone of xyloglucan [22,23], and several CSLD mutants have been characterized for their potential roles in wall polysaccharide (xylan and homogalacturonan) synthesis [24,25,26,27]. The detailed functions of these CSL genes, especially those of families CSLB, E and G, remain to be clarified
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