A receptor-like kinase mediates the response of Arabidopsis cells to the inhibition of cellulose synthesis.

BACKGROUND: A major challenge is to understand how the walls of expanding plant cells are correctly assembled and remodeled, often in the presence of wall-degrading micro-organisms. Plant cells, like yeast, react to cell-wall perturbations as shown by changes in gene expression, accumulation of ectopic lignin, and growth arrest caused by the inhibition of cellulose synthesis. RESULTS: We have identified a plasma-membrane-bound receptor-like kinase (THESEUS1), which is present in elongating cells. Mutations in THE1 and overexpression of a functional THE1-GFP fusion protein did not affect wild-type (WT) plants but respectively attenuated and enhanced growth inhibition and ectopic lignification in seedlings mutated in cellulose synthase CESA6 without influencing the cellulose deficiency. A T-DNA insertion mutant for THE1 also attenuated the growth defect and ectopic-lignin production in other but not all cellulose-deficient mutants. The deregulation of a small number of genes in cesA6 mutants depended on the presence of THE1. Some of these genes are involved in pathogen defense, in wall crosslinking, or in protecting the cell against reactive oxygen species. CONCLUSIONS: The results show that THE1 mediates the response of growing plant cells to the perturbation of cellulose synthesis and may act as a cell-wall-integrity sensor.

Integrating genes and phenotype: a wheat-Arabidopsis-rice glycosyltransferase database for candidate gene analyses.

Glycosyltransferases (GTs) constitute a very large multi-gene superfamily, containing several thousand members identified in sequenced organisms especially in plants. GTs are key enzymes involved in various biological processes such as cell wall formation, storage polysaccharides biosynthesis, and glycosylation of various metabolites. GTs have been identified in rice (Oryza sativa) and Arabidopsis thaliana, but their precise function has been demonstrated biochemically for only a few. In this work we have established a repertoire of virtually all the wheat (Triticum aestivum) GT sequences, using the large publicly available banks of expressed sequences. Based on sequence similarity with Arabidopsis and rice GTs compiled in the carbohydrate active enzyme database (CAZY), we have identified and classified these wheat sequences. The results were used to feed a searchable database available on the web ( http://wwwappli.nantes.inra.fr:8180/GTIDB ) that can be used for initiating an exhaustive candidate gene survey in wheat applied to a particular biological process. This is illustrated through the identification of GT families which are expressed during cell wall formation in wheat grain maturation.

Early gene expression associated with the commitment and differentiation of a plant tracheary element is revealed by cDNA-amplified fragment length polymorphism analysis.

Isolated mesophyll cells from Zinnia elegans are induced by auxin and cytokinin to form tracheary elements (TEs) in vitro with high synchrony. To reveal the changing patterns of gene expression during the 48 h of transdifferentiation from mesophyll to TE cell fate, we used a cDNA-amplified fragment length polymorphism approach to generate expression profiles of >30,000 cDNA fragments. Transcriptional changes of 652 cDNA fragments were observed, of which 304 have no previously described function or sequence identity. Sixty-eight genes were upregulated within 30 min of induction and represent key candidates for the processes that underlie the early stages of commitment and differentiation to a TE cell fate.