ZmXTH1, a new xyloglucan endotransglucosylase/hydrolase in maize, affects cell wall structure and composition in Arabidopsis thaliana

15 pages, 9 figures.-- PMID: 18316315[PubMed].-- Supporting information available at: http://jxb.oxfordjournals.org/content/59/4/875/suppl/DC1Xyloglucan endotransglucosylase/hydrolases (XTHs; EC 2.4.1.207 and/or EC 3.2.1.151) are enzymes involved in the modification of cell wall structure by cleaving and, often, also re-joining xyloglucan molecules in primary plant cell walls. Using a pool of antibodies raised against an enriched cell wall protein fraction, a new XTH cDNA in maize, ZmXTH1, has been isolated from a cDNA expression library obtained from the elongation zone of the maize root. The predicted protein has a putative N-terminal signal peptide and possesses the typical domains of this enzyme family, such as a catalytic domain that is homologous to that of Bacillus macerans beta-glucanase, a putative N-glycosylation motif, and four cysteine residues in the central and C terminal regions of the ZmXTH1 protein. Phylogenetic analysis of ZmXTH1 reveals that it belongs to subgroup 4, so far only reported from Poaceae monocot species. ZmXTH1 has been expressed in Pichia pastoris (a methylotrophic yeast) and the recombinant enzyme showed xyloglucan endotransglucosylase but not xyloglucan endohydrolase activity, representing the first enzyme belonging to subgroup 4 characterized in maize so far. Expression data indicate that ZmXTH1 is expressed in elongating tissues, modulated by culture conditions, and induced by gibberellins. Transient expression assays in onion cells reveal that ZmXTH1 is directed to the cell wall, although weakly bound. Finally, Arabidopsis thaliana plants expressing ZmXTH1 show slightly increased xyloglucan endohydrolase activity and alterations in the cell wall structure and composition.This work was funded by the Spanish ‘Ministerio de Ciencia y Tecnología’ (BIO2001-1140). VG was financed by a pre-doctoral grant from the ‘Generalitat de Catalunya’ (2003-FI00090). In addition, VG was funded by two grants from the Generalitat de Catalunya (2005-BE00104 and 2006-BE00668) for her work performed at Professor Fry's and Dr Ruel's laboratories. SF was financed by a post-doctoral grant from the ‘Generalitat de Catalunya’ (2003PIV-A-00033) and by an I3P contract from the ‘Consejo Superior de Investigaciones Científicas’. DC-R was financed by the Spanish ‘Ministerio de Educacion y Ciencia’ (‘Ramon y Cajal’ Program). This work was carried out within the framework of the ‘Xarxa de Referència en Biotecnologia’ from the ‘Generalitat de Catalunya’. SCF was funded by the UK Biotechnology and Biological Sciences Research Council. We are indebted to Dr Castresana (IBMB-CSIC) for his advice on the phylogenetic analyses, Dr Capellades for her technical support and the sequencing, and the greenhouse teams of IBMB-CSIC.Peer reviewe

Correction to: Cluster identification, selection, and description in Cluster randomized crossover trials: the PREP-IT trials

An amendment to this paper has been published and can be accessed via the original article

A Plant snoRNP Complex Containing snoRNAs, Fibrillarin, and Nucleolin-Like Proteins Is Competent for both rRNA Gene Binding and Pre-rRNA Processing In Vitro

In eukaryotes the primary cleavage of the precursor rRNA (pre-rRNA) occurs in the 5′ external transcribed spacer (5′ETS). In Saccharomyces cerevisiae and animals this cleavage depends on a conserved U3 small nucleolar ribonucleoprotein particle (snoRNP), including fibrillarin, and on other transiently associated proteins such as nucleolin. This large complex can be visualized by electron microscopy bound to the nascent pre-rRNA soon after initiation of transcription. Our group previously described a radish rRNA gene binding activity, NF D, that specifically binds to a cluster of conserved motifs preceding the primary cleavage site in the 5′ETS of crucifer plants including radish, cauliflower, and Arabidopsis thaliana (D. Caparros-Ruiz, S. Lahmy, S. Piersanti, and M. Echeverria, Eur. J. Biochem. 247:981-989, 1997). Here we report the purification and functional characterization of NF D from cauliflower inflorescences. Remarkably NF D also binds to 5′ETS RNA and accurately cleaves it at the primary cleavage site mapped in vivo. NF D is a multiprotein factor of 600 kDa that dissociates into smaller complexes. Two polypeptides of NF D identified by microsequencing are homologues of nucleolin and fibrillarin. The conserved U3 and U14 snoRNAs associated with fibrillarin and required for early pre-rRNA cleavages are also found in NF D. Based on this it is proposed that NF D is a processing complex that assembles on the rDNA prior to its interaction with the nascent pre-rRNA

Interplay between the NADP-Linked Thioredoxin and Glutathione Systems in Arabidopsis Auxin Signaling[C][W]

NADP-linked thioredoxin and glutathione systems are key reduction pathways in living organisms. Based on a genetic approach, this study shows that these pathways interfere with auxin transport and metabolism, defining a link between redox regulation and auxin signaling

Elucidating compositional factors of maize cell walls contributing to stalk strength and lodging resistance

Lodging is one of the causes of maize (Zea mays L.) production losses worldwide and, at least, the resistance to stalk lodging has been positively correlated with stalk strength. In order to elucidate the putative relationship between cell wall, stalk strength and lodging resistance, twelve maize inbreds varying in rind penetration strength and lodging resistance were characterized for cell wall composition and structure. Stepwise multiple regression indicates that H lignin subunits confer a greater rind penetration strength. Besides, the predictive model for lodging showed that a high ferulic acid content increases the resistance to lodging, whereas those of diferulates decrease it. These outcomes highlight that the strength and lodging susceptibility of maize stems may be conditioned by structural features of cell wall rather than by the net amount of cellulose, hemicelluloses and lignin. The results presented here provide biotechnological targets in breeding programs aimed at improving lodging in maize.info:eu-repo/semantics/acceptedVersio

Libertà religiosa e non discriminazione in ambito lavorativo in Italia

Analisi delle forme di discriminazione diretta e indiretta nel settore lavorativo tanto pubblico quanto privato motivate da ragioni tanto feligiose quanto culturali. Analis della normativa italiana e della influenza delle direttive europee al riguard

Cell wall modifications triggered by the down-regulation of Coumarate 3-hydroxylase-1 in maize

Coumarate 3-hydroxylase (C3H) catalyzes a key step of the synthesis of the two main lignin subunits, guaiacyl (G) and syringyl (S) in dicotyledonous species. As no functional data are available in regards to this enzyme in monocotyledonous species, we generated C3H1 knock-down maize plants. The results obtained indicate that C3H1 participates in lignin biosynthesis as its down-regulation redirects the phenylpropanoid flux: as a result, increased amounts of p-hydroxyphenyl (H) units, lignin-associated ferulates and the flavone tricin were detected in transgenic stems cell walls. Altogether, these changes make stem cell walls more degradable in the most C3H1-repressed plants, despite their unaltered polysaccharide content. The increase in H monomers is moderate compared to C3H deficient Arabidopsis and alfalfa plants. This could be due to the existence of a second maize C3H protein (C3H2) that can compensate the reduced levels of C3H1 in these C3H1-RNAi maize plants. The reduced expression of C3H1 alters the macroscopic phenotype of the plants, whose growth is inhibited proportionally to the extent of C3H1 repression. Finally, the down-regulation of C3H1 also increases the synthesis of flavonoids, leading to the accumulation of anthocyanins in transgenic leaves.Funding: This work was supported by the Spanish “Ministerio de Economía y Competitividad” [AGL2011-30545-C02-01 to D.C.-R., AGL2011-30545-C02-02 to A.E., and AGL2011-25379 (co-financed by FEDER funds) to J.C.R.] and received financial support from the CONSOLIDER-INGENIO program [CSD2007-00036] from the Spanish Ministerio de Ciencia e Innovación. This work was carried out within the framework of the “Xarxa de Referència de Biotecnologia” (XarBa) from the Autonomous Government of Catalonia. R.S. was financed by the postdoctoral contracts “Isidro Parga Pondal” supported by the Autonomous Government of Galicia and the European Social Fund and “Ramón y Cajal”, supported by the Spanish Ministry of Economy and Competitiveness and the University of Vigo. J.R. thanks CSIC for a JAE-DOC contract of the program “Junta para la Ampliación de Estudios” co-financed by the European Social Fund.Peer Reviewe