Expression of cell wall related genes in basal and ear internodes of silking brown-midrib-3, caffeic acid O-methyltransferase (COMT) down-regulated, and normal maize plants

<p>Abstract</p> <p>Background</p> <p>Silage maize is a major forage and energy resource for cattle feeding, and several studies have shown that lignin content and structure are the determining factors in forage maize feeding value. In maize, four natural <it>brown-midrib </it>mutants have modified lignin content, lignin structure and cell wall digestibility. The greatest lignin reduction and the highest cell wall digestibility were observed in the <it>brown-midrib-3 </it>(<it>bm3</it>) mutant, which is disrupted in the caffeic acid <it>O</it>-methyltransferase (COMT) gene.</p> <p>Results</p> <p>Expression of cell wall related genes was investigated in basal and ear internodes of normal, COMT antisens (AS225), and <it>bm3 </it>maize plants of the INRA F2 line. A cell wall macro-array was developed with 651 gene specific tags of genes specifically involved in cell wall biogenesis. When comparing basal (older lignifying) and ear (younger lignifying) internodes of the normal line, all genes known to be involved in constitutive monolignol biosynthesis had a higher expression in younger ear internodes. The expression of the COMT gene was heavily reduced, especially in the younger lignifying tissues of the ear internode. Despite the fact that AS225 transgene expression was driven only in sclerenchyma tissues, COMT expression was also heavily reduced in AS225 ear and basal internodes. COMT disruption or down-regulation led to differential expressions of a few lignin pathway genes, which were all over-expressed, except for a phenylalanine ammonia-lyase gene. More unexpectedly, several transcription factor genes, cell signaling genes, transport and detoxification genes, genes involved in cell wall carbohydrate metabolism and genes encoding cell wall proteins, were differentially expressed, and mostly over-expressed, in COMT-deficient plants.</p> <p>Conclusion</p> <p>Differential gene expressions in COMT-deficient plants highlighted a probable disturbance in cell wall assembly. In addition, the gene expressions suggested modified chronology of the different events leading to cell expansion and lignification with consequences far beyond the phenylpropanoid metabolism. The reduced availability of monolignols and S units in <it>bm3 </it>or AS225 plants led to plants also differing in cell wall carbohydrate, and probably protein, composition. Thus, the deficiency in a key-enzyme of the lignin pathway had correlative effects on the whole cell wall metabolism. Furthermore, the observed differential expression between <it>bm3 </it>and normal plants indicated the possible involvement in the maize lignin pathway of genes which up until now have not been considered to play this role.</p

Maize cell wall degradability, from whole plant to tissue level: different scales of complexity

Today, maize stover can be considered as a model for investigating secondary cell wall formation in grasses with major applications in cattle feeding (forage maize) and green energy production (bioethanol, biogas, etc). Up until now, cell wall formation and cell wall degradability have been considered at the whole plant scale. However, a detailed examination of leaves and internodes has underlined a large diversity of lignified cell types (xylem vessels, parenchyma, sub-epidermal and perivascular sclerenchyma) and significant variations in the organization and / or the composition of these different cell types. In this review, we highlighted several aspects of this complexity and their consequences on valorization processes both in agriculture or industries

Characterization of a cinnamoyl-CoA reductase 1 (CCR1) mutant in maize: effects on lignification, fibre development, and global gene expression

Cinnamoyl-CoA reductase (CCR), which catalyses the first committed step of the lignin-specific branch of monolignol biosynthesis, has been extensively characterized in dicot species, but few data are available in monocots. By screening a Mu insertional mutant collection in maize, a mutant in the CCR1 gene was isolated named Zmccr1–. In this mutant, CCR1 gene expression is reduced to 31% of the residual wild-type level. Zmccr1– exhibited enhanced digestibility without compromising plant growth and development. Lignin analysis revealed a slight decrease in lignin content and significant changes in lignin structure. p-Hydroxyphenyl units were strongly decreased and the syringyl/guaiacyl ratio was slightly increased. At the cellular level, alterations in lignin deposition were mainly observed in the walls of the sclerenchymatic fibre cells surrounding the vascular bundles. These cell walls showed little to no staining with phloroglucinol. These histochemical changes were accompanied by an increase in sclerenchyma surface area and an alteration in cell shape. In keeping with this cell type-specific phenotype, transcriptomics performed at an early stage of plant development revealed the down-regulation of genes specifically associated with fibre wall formation. To the present authors’ knowledge, this is the first functional characterization of CCR1 in a grass species

Des verres carolingiens de compositions atypiques à Bressuire et Faye-sur-Ardin (nord de la région melloise, Deux-Sèvres).

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Novel markers of xylogenesis in Zinnia elegans are differentially regulated by auxin and cytokinin

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Novel Markers of Xylogenesis in Zinnia Are Differentially Regulated by Auxin and Cytokinin

The characterization of in vitro xylogenic cultures of zinnia (Zinnia elegans) has led to major discoveries in the understanding of xylem formation in plants. We have constructed and characterized a subtractive library from zinnia cultures enriched in genes that are specifically expressed at the onset of secondary wall deposition and tracheary element (TE) programmed cell death. This Late Xylogenesis Library (LXL) consisted of 236 nonredundant cDNAs, 77% of which encoded novel sequences in comparison with the 17,622 expressed sequence tag sequences publicly available. cDNA arrays were constructed to examine dynamic global gene expression during the course of TE formation. As a first step in dissecting auxin and cytokinin signaling during TE differentiation, macroarrays were probed with cDNAs from cells cultured in different hormonal conditions. Fifty-one percent of the LXL genes were induced by either auxin or cytokinin individually, the large majority by auxin. To determine the potential involvement of these categories of genes in TE differentiation, multiplex in situ-reverse transcription-PCR was performed on cells for two genes encoding putative cell wall proteins: Gibberellin stimulated transcript-1, induced by auxin alone, and expansin 5, induced by cytokinin alone. All transcriptionally active TEs expressed both genes, indicating that, although these genes may not be considered as specific markers for TE differentiation per se, they are nevertheless an integral part of TE differentiation program. Among the non-TE population, four different gene expression-based cell types could be distinguished. Together, these results demonstrate the underlying complexity of hormonal perception and the existence of several different cell types in in vitro TE cell cultures

Novel markers of xylogenesis in Zinnia elegans are differentially regulated by auxin and cytokinin

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Prenatal cannabinoid exposure alters the ovarian reserve in adult offspring of rats

International audienceIn animals, research in the past two decades has demonstrated the strong involvement of the endocannabinoid system (ECS) in numerous steps of the reproductive process, including ovarian physiology. Reproductive lifespan is closely related to the number of nongrowing ovarian follicles, called ovarian reserve (OR), which is definitively established during foetal life. Thus, OR damage may lead to poor reproductive outcomes and a shortened reproductive lifespan. We investigated whether prenatal ECS modulation had an effect on the OR at different ages in the rat offspring. Four groups of gestating female rats (F0) were exposed to the CB1-/CB2-receptor agonist WIN55212 (0.5 mg/kg), the CB1R inverse agonist SR141716 (3 mg/kg) or Δ9THC (5 mg/kg) and were compared to negative control groups. OR was histologically assessed at different postnatal timepoints (F1 individuals): postnatal day (PND) 6, PND40 and PND90. At PND6, prenatal exposure had no effect on OR. In the young adult group (PND90) exposed during gestation to WIN55212, we observed a CB1R-mediated delayed OR decrease, which was reversed by prenatal CB1R blockade by SR141716. Conversely, after prenatal SR141716 exposure, we observed higher OR counts at PND90. RT-PCR experiments also showed that prenatal ECS modulation perturbed the mRNA levels of ECS enzymes and OR regulation genes. Our findings support the role of the ECS in OR regulation during the foetal life of rats and highlight the need for further studies to elucidate its precise role in OR physiology

Expression of cell wall related genes in basal and ear internodes of silking , caffeic acid -methyltransferase (COMT) down-regulated, and normal maize plants-1

Ernodes from normal, and AS225 silking stage plants. 18S rRNA was used as a quantitative control.<p><b>Copyright information:</b></p><p>Taken from "Expression of cell wall related genes in basal and ear internodes of silking , caffeic acid -methyltransferase (COMT) down-regulated, and normal maize plants"</p><p>http://www.biomedcentral.com/1471-2229/8/71</p><p>BMC Plant Biology 2008;8():71-71.</p><p>Published online 26 Jun 2008</p><p>PMCID:PMC2453129.</p><p></p

Expression of cell wall related genes in basal and ear internodes of silking , caffeic acid -methyltransferase (COMT) down-regulated, and normal maize plants-0

Ld plants stained with Maüle reagent (A-B). Light microscopy observations of transverse sections in bottom part of ear internode in silking plants stained with Wiesner reagent (D, F, H). UV illumination of ear internode bottom part in silking plants (E, G, I). Differences in coloration of lignified tissues between F2, AS225 and F2lines in the presence of Maüle reagent (A-C) are visible. Metaxylem vessels of ear internode transverse sections (D-I) of AS225 and F2plants also had a modified lignification (arrow). x = xylem; s = sclerenchyma; p = parenchyma; pp = protophloem; px = protoxylem; mx = metaxylem. Magnification bar was 100 μm (A-C) or 50 μm (D-I).<p><b>Copyright information:</b></p><p>Taken from "Expression of cell wall related genes in basal and ear internodes of silking , caffeic acid -methyltransferase (COMT) down-regulated, and normal maize plants"</p><p>http://www.biomedcentral.com/1471-2229/8/71</p><p>BMC Plant Biology 2008;8():71-71.</p><p>Published online 26 Jun 2008</p><p>PMCID:PMC2453129.</p><p></p