Developmental Expression Patterns of Arabidopsis XTH Genes Reported by Transgenes and Genevestigator

Abstract

The plant cell wall is the structural basis of cellular form and thus forms a foundation on which morphogenesis builds organs and tissues. Enzymes capable of modifying major wall components are prominent candidates for regulating wall form and function. Xyloglucan endotransglucosylases/hydrolases (XTHs) are predicted to participate in xyloglucan integration and/or restructuring. XTHs are encoded by large gene families in plants; the Arabidopsis genome encodes 33 XTHs. To gain insight into the potential physiological relevance of the distinct members of this family, GUS reporter fusion genes were constructed, and plants expressing these transgenes were characterized to reveal spatial and temporal patterns of expression. In addition, Genevestigator sources were mined for comprehensive and comparative XTH expression regulation analysis. These data reveal that the Arabidopsis XTHs are likely expressed in every developmental stage from seed germination through flowering. All organs show XTH::GUS expression and most, if not all, are found to express multiple XTH::GUS genes. These data suggest that XTHs may contribute to morphogenesis at every developmental stage and in every plant organ. Different XTHs have remarkably diverse and distinct expression patterns indicating that paralogous genes have evolved differential expression regulation perhaps contributing to the maintenance of the large gene family. Extensive overlap in XTH expression patterns is evident; thus, XTHs may act combinatorially in determining wall properties of specific tissues or organs. Knowledge of gene-specific expression among family members yields evidence of where and when gene products may function and provides insights to guide rational approaches to investigate function through reverse genetics.

Group III-AXTHGenes of Arabidopsis Encode Predominant Xyloglucan Endohydrolases That Are Dispensable for Normal Growth

“…AtXTH31, on the other hand, appears to be highly to very highly expressed in tissues undergoing elongation: hypocotyl, radicle, root elongation zone, and lateral root. In support of these data, AtXTH31::GUS transgenic Arabidopsis plant lines have previously been shown to exhibit prominent staining in roots, whereas AtXTH32:: GUS lines were stained prominently in the shoot apex of older seedlings (Becnel et al, 2006).…”

“…Here, AtXTH31 may be the dominant player in Col-0, as it is significantly up-regulated (Supplemental Fig. S5B) in both imbibed seeds (absolute expression value [AEV] 8,300) and the radicle (AEV 11,000), whereas AtXTH32 has very low-level expression (AEV 880 and 590, respectively, as supported by promoter-GUS analysis [Becnel et al, 2006]). …”

“…Organ-specific and temporal expression patterns of all 33 Arabidopsis (ecotype Columbia ) XTH genes from Genevestigator data (Zimmermann et al, 2004) have previously been analyzed in detail, in connection with extensive reporter gene fusion data (Becnel et al, 2006). In this study, Genevestigator expression levels of AtXTH31 (At3g44990) and AtXTH32 (At2g36870) were reevaluated to take advantage of the current larger data set.…”

Coordination between Apoplastic and Symplastic Detoxification Confers Plant Aluminum Resistance

“…S2B), indicating that the xth15 allele is likely a null mutation. XTH15 is likely to function in seedling roots because strong root staining is found in transgenics harboring a GUS reporter gene driven by the XTH15 59 potential regulatory region (Becnel et al, 2006). We examined the two different mutants, the auxinoverproducing mutant, yucca, and the cell wall mutant, xth15, which showed large differences in aluminum sensitivity despite having similar root aluminum content.…”

Organelle–nucleus cross-talk regulates plant intercellular communication via plasmodesmata

“…Eight of these genes are differentially regulated in ise1 and/or ise2 compared with WT (Table 2). XTH19 has been reported as root-specific (36,37), yet it is strongly induced in both mutants. Indeed, XTH19 is the most strongly induced gene in ise1 (50-fold higher than WT levels), and it is also strongly induced in ise2 (15-fold WT levels).…”