Synchronized communication between gametophytic and sporophytic tissue is crucial for successful reproduction, and hormones seem to have a prominent role in it. Here, we studied the role of the Arabidopsis (Arabidopsis thaliana) cytochrome P450 CYP78A9 enzyme during reproductive development. First, controlled pollination experiments indicate that CYP78A9 responds to fertilization. Second, while CYP78A9 overexpression can uncouple fruit development from fertilization, the cyp78a8 cyp78a9 loss-of-function mutant has reduced seed set due to outer ovule integument development arrest, leading to female sterility. Moreover, CYP78A9 has a specific expression pattern in inner integuments in early steps of ovule development as well as in the funiculus, embryo, and integuments of developing seeds. CYP78A9 overexpression did not change the response to the known hormones involved in flower development and fruit set, and it did not seem to have much effect on the major known hormonal pathways. Furthermore, according to previous predictions, perturbations in the flavonol biosynthesis pathway were detected in cyp78a9, cyp78a8 cyp78a9, and empty siliques (es1-D) mutants. However, it appeared that they do not cause the observed phenotypes. In summary, these results add new insights into the role of CYP78A9 in plant reproduction and present, to our knowledge, the first characterization of metabolite differences between mutants in this gene family.Angiosperms have evolved the processes of double fertilization and fruit development as pivotal steps of their survival and dispersal strategies. Pollination and fertilization are essential for fruit initiation, considering that the angiosperm flower initiates terminal senescence and abscission programs if pollination has not taken place (Vivian-Smith et al., 2001; Fuentes and VivianSmith, 2009). For centuries, humans endeavored to prevent this association in order to develop seedless fruits. Most research has concentrated on the role of endogenous phytohormones as triggers for fruit initiation after fertilization, and different strategies such as exogenous application or artificial overproduction of plant hormones (Fuentes and Vivian-Smith, 2009), mutation, and misexpression of specific genes have been tested. The principal lines of evidence suggest that increased auxin and GA content in ovules and ovary leads to parthenocarpic fruits in Arabidopsis (Arabidopsis thaliana;

In mammals, cadmium is widely considered as a non-genotoxic carcinogen acting through a methylation-dependent epigenetic mechanism. Here, the effects of Cd treatment on the DNA methylation patten are examined together with its effect on chromatin reconfiguration in Posidonia oceanica. DNA methylation level and pattern were analysed in actively growing organs, under short-(6 h) and long-(2 d or 4 d) term and low (10 mM) and high (50 mM) doses of Cd, through a Methylation-Sensitive Amplification Polymorphism technique and an immunocytological approach, respectively. The expression of one member of the CHROMOMETHYLASE (CMT) family, a DNA methyltransferase, was also assessed by qRT-PCR. Nuclear chromatin ultrastructure was investigated by transmission electron microscopy. Cd treatment induced a DNA hypermethylation, as well as an up-regulation of CMT, indicating that de novo methylation did indeed occur. Moreover, a high dose of Cd led to a progressive heterochromatinization of interphase nuclei and apoptotic figures were also observed after long-term treatment. The data demonstrate that Cd perturbs the DNA methylation status through the involvement of a specific methyltransferase. Such changes are linked to nuclear chromatin reconfiguration likely to establish a new balance of expressed/repressed chromatin. Overall, the data show an epigenetic basis to the mechanism underlying Cd toxicity in plants.

The crystal structure of the GH78 family a-rhamnosidase from Klebsiella oxytoca (KoRha) has been determined at 2.7 Å resolution with rhamnose bound in the active site of the catalytic domain. Curiously, the putative catalytic acid, Asp 222, is preceded by an unusual non-proline cis-peptide bond which helps to project the carboxyl group into the active centre. This KoRha homodimeric structure is significantly smaller than those of the other previously determined GH78 structures. Nevertheless, the enzyme displays a-rhamnosidase activity when assayed in vitro, suggesting that the additional structural domains found in the related enzymes are dispensible for function.

In the post-genomic era much effort has been put on the discovery of gene function using functional genomics. Despite the advances achieved by these technologies in the understanding of gene function at the genomic and proteomic level, there is still a big genotype-phenotype gap. Metabolic profiling has been used to analyze organisms that have already been characterized genetically. However, there is a small number of studies comparing the metabolic profile of different tissues of distinct accessions. Here, we report the detection of over 14,000 and 17,000 features in inflorescences and leaves, respectively, in two widely used Arabidopsis thaliana accessions. A predictive Random Forest Model was developed, which was able to reliably classify tissue type and accession of samples based on LC-MS profile. Thereby we demonstrate that the morphological differences among A. thaliana accessions are reflected also as distinct metabolic phenotypes within leaves and inflorescences.

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Pectic polysaccharide RG-II, a key component of plant primary cell walls, is known to exist as a dimer formed by means of borate diester cross-links between apiosyl residues of one of its constituent side-chain oligosaccharides. Described herein is the strategy for the synthesis of the branched tetrasaccharide alpha-d-GalA-(1-->2)-[beta-D-GalA-(1-->3)]-[alpha-L-Fuc-(1-->4)]-alpha-L-Rha-OMe, an RG-II fragment that is linked to the apiosyl residue that is thought to be responsible for the borate complexation in RG-II dimer. Iterative glycosylation of the rhamnoside acceptors derived from the key 2,3-orthoacetate of methyl 4-O-methoxybenzyl-alpha-d-rhamnopyranoside afforded the protected tetrasaccharide. The target dicarboxylic acid saccharide was subsequently prepared by removal of protecting groups followed by TEMPO-mediated oxidation of galactopyranosyl residues to galactopyranosyluronic acids.

Table of ContentsS11 Methyl 2-O-acetyl-4-O-(4-methoxybenzyl)-α-L-rhamnopyranoside (10) S13

International audienceAn extensive study on the specificity of transglycosylation and disproportionation of Thermoanaerobacterium sp. cyclodextrin glucosyltranferases against aryl glucopyranosides or furanosides was achieved. While a mixture of maltoside and isomaltoside was obtained respectively using p-nitrophenyl glucopyranoside as acceptor, only one regioisomer, namely the p-nitrophenyl α-D-Glcp-(1,3)-α-L-Araf was isolated using p-nitrophenyl arabinofuranoside as acceptor. Interestingly, similar outcomes were found when using p-nitrophenyl galactofuranoside. Furthermore, activation by microwave irradiation resulted in faster reaction times and higher yields and led to glucosidic oligosaccharides with up to 70% conversion. The influence of the anomeric and C-4 configurations of the glycosidic acceptors on the transglycosylation, previously stated for the CGTase family, was not observed and unconventional substrate specificity towards alkyl furanosides was highlighted