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Our previous study of the Arabidopsis mur3-3 mutant and mutant plants in which the mur3-3 phenotypes are suppressed ( xxt2mur3-3 , xxt5mur3-3 , xxt1xxt2mur3-3 and 35S pro : XLT2 : mur3-3 ) showed that hypocotyl cell elongation is decreased in plants that synthesize galactose-deficient xyloglucan. To obtain genome-wide insight into the transcriptome changes and regulatory networks that may be involved in this decreased elongation, we performed digital gene expression analyses of the etiolated hypocotyls of wild type (WT), mur3-3 and the four suppressor lines. Numerous differentially expressed genes (DEGs) were detected in comparisons between WT and mur3-3 (1423), xxt2mur3-3 and mur3-3 (675), xxt5mur3-3 and mur3-3 (1272), xxt1xxt2mur3-3 and mur3-3 (1197) and 35S pro : XLT2 : mur3-3 vs mur3-3 (121). 550 overlapped DEGs were detected among WT vs mur3-3 , xxt2mur3-3 vs mur3-3 , xxt5mur3-3 vs mur3-3 , and xxt1xxt2mur3-3 vs mur3-3 comparisons. These DEGs include 46 cell wall-related genes, 24 transcription factors, 6 hormone-related genes, 9 protein kinase genes and 9 aquaporin genes. The expression of all of the 550 overlapped genes is restored to near wild-type levels in the four mur3-3 suppressor lines. qRT-PCR of fifteen of these 550 genes showed that their expression levels are consistent with the digital gene expression data. Overexpression of some of these genes ( XTH4 , XTH30 , PME3 , EXPA11 , MYB88 , ROT3 , AT5G37790 , WAG2 and TIP2;3 ) that are down-regulated in mur3-3 partially rescued the short hypocotyl phenotype but not the aerial phenotype of mur3-3 , indicating that different mechanisms exist between hypocotyl cell elongation and leaf cell elongation. [ABSTRACT FROM AUTHOR]

Abstract: Fruit development is a highly complex process, which involves major changes in plant metabolism leading to cell growth and differentiation. Changes in cell wall composition and structure play a major role in modulating cell growth. We investigated the changes in cell wall composition and the activities of associated enzymes during the dry fruit development of the model plant Arabidopsis thaliana. Silique development is characterized by several specific phases leading to fruit dehiscence and seed dispersal. We showed that early phases of silique growth were characterized by specific changes in non-cellulosic sugar content (rhamnose, arabinose, xylose, galactose and galacturonic acid). Xyloglucan oligosaccharide mass profiling further showed a strong increase in O-acetylated xyloglucans over the course of silique development, which could suggest a decreased capacity of xyloglucans to be associated with each other or to cellulose. The degree of methylesterification, mediated by the activity of pectin methylesterases (PMEs), decreased over the course of silique growth and dehiscence. The major changes in cell wall composition revealed by our analysis suggest that it could be major determinants in modulating cell wall rheology leading to growth or growth arrest. [Copyright &y& Elsevier]