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Publications - Cell and Metabolic Biology

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Displaying results 201 to 210 of 480.

Publications

Wasternack, C.; Goetz, S.; Hellwege, A.; Forner, S.; Strnad, M.; Hause, B.; Another JA/COI1-independent role of OPDA detected in tomato embryo development Plant Signal Behav. 7, 1349-1353, (2012) DOI: 10.4161/psb.21551

Jasmonates (JAs) are ubiquitously occurring signaling compounds in plants formed in response to biotic and abiotic stress as well as in development. (+)-7-iso-jasmonoyl isoleucine, the bioactive JA, is involved in most JA-dependent processes mediated by the F-box protein COI1 in a proteasome-dependent manner. However, there is an increasing number of examples, where the precursor of JA biosynthesis, cis-(+)-12-oxophytodienoic acid (OPDA) is active in a JA/COI1-independent manner. Here, we discuss those OPDA-dependent processes, thereby giving emphasis on tomato embryo development. Recent data on seed coat-generated OPDA and its role in embryo development is discussed based on biochemical and genetic evidences.
Publications

Vadassery, J.; Reichelt, M.; Hause, B.; Gershenzon, J.; Boland, W.; Mithöfer, A.; CML42-Mediated Calcium Signaling Coordinates Responses to Spodoptera Herbivory and Abiotic Stresses in Arabidopsis Plant Physiol. 159, 1159-1175, (2012) DOI: 10.1104/pp.112.198150

In the interaction between Arabidopsis (Arabidopsis thaliana) and the generalist herbivorous insect Spodoptera littoralis, little is known about early events in defense signaling and their link to downstream phytohormone pathways. S. littoralis oral secretions induced both Ca2+ and phytohormone elevation in Arabidopsis. Plant gene expression induced by oral secretions revealed up-regulation of a gene encoding a calmodulin-like protein, CML42. Functional analysis of cml42 plants revealed more resistance to herbivory than in the wild type, because caterpillars gain less weight on the mutant, indicating that CML42 negatively regulates plant defense; cml42 also showed increased aliphatic glucosinolate content and hyperactivated transcript accumulation of the jasmonic acid (JA)-responsive genes VSP2 and Thi2.1 upon herbivory, which might contribute to increased resistance. CML42 up-regulation is negatively regulated by the jasmonate receptor Coronatine Insensitive1 (COI1), as loss of functional COI1 resulted in prolonged CML42 activation. CML42 thus acts as a negative regulator of plant defense by decreasing COI1-mediated JA sensitivity and the expression of JA-responsive genes and is independent of herbivory-induced JA biosynthesis. JA-induced Ca2+ elevation and root growth inhibition were more sensitive in cml42, also indicating higher JA perception. Our results indicate that CML42 acts as a crucial signaling component connecting Ca2+ and JA signaling. CML42 is localized to cytosol and nucleus. CML42 is also involved in abiotic stress responses, as kaempferol glycosides were down-regulated in cml42, and impaired in ultraviolet B resistance. Under drought stress, the level of abscisic acid accumulation was higher in cml42 plants. Thus, CML42 might serve as a Ca2+ sensor having multiple functions in insect herbivory defense and abiotic stress responses.
Publications

Tissier, A.; Glandular trichomes: what comes after expressed sequence tags? Plant J. 70, 51-68, (2012) DOI: 10.1111/j.1365-313X.2012.04913.x

Glandular trichomes cover the surface of many plant species. They exhibit tremendous diversity, be it in their shape or the compounds they secrete. This diversity is expressed between species but also within species or even individual plants. The industrial uses of some trichome secretions and their potential as a defense barrier, for example against arthropod pests, has spurred research into the biosynthesis pathways that lead to these specialized metabolites. Because complete biosynthesis pathways take place in the secretory cells, the establishment of trichome‐specific expressed sequence tag libraries has greatly accelerated their elucidation. Glandular trichomes also have an important metabolic capacity and may be considered as true cell factories. To fully exploit the potential of glandular trichomes as breeding or engineering objects, several research areas will have to be further investigated, such as development, patterning, metabolic fluxes and transcription regulation. The purpose of this review is to provide an update on the methods and technologies which have been used to investigate glandular trichomes and to propose new avenues of research to deepen our understanding of these specialized structures.
Publications

Stenzel, I.; Otto, M.; Delker, C.; Kirmse, N.; Schmidt, D.; Miersch, O.; Hause, B.; Wasternack, C.; ALLENE OXIDE CYCLASE (AOC) gene family members of Arabidopsis thaliana: tissue- and organ-specific promoter activities and in vivo heteromerization J. Exp. Bot. 63, 6125-6138, (2012) DOI: 10.1093/jxb/ers261

Jasmonates are important signals in plant stress responses and plant development. An essential step in the biosynthesis of jasmonic acid (JA) is catalysed by ALLENE OXIDE CYCLASE (AOC) which establishes the naturally occurring enantiomeric structure of jasmonates. In Arabidopsis thaliana, four genes encode four functional AOC polypeptides (AOC1, AOC2, AOC3, and AOC4) raising the question of functional redundancy or diversification. Analysis of transcript accumulation revealed an organ-specific expression pattern, whereas detailed inspection of transgenic lines expressing the GUS reporter gene under the control of individual AOC promoters showed partially redundant promoter activities during development: (i) In fully developed leaves, promoter activities of AOC1, AOC2, and AOC3 appeared throughout all leaf tissue, but AOC4 promoter activity was vascular bundle-specific; (ii) only AOC3 and AOC4 showed promoter activities in roots; and (iii) partially specific promoter activities were found for AOC1 and AOC4 in flower development. In situ hybridization of flower stalks confirmed the GUS activity data. Characterization of single and double AOC loss-of-function mutants further corroborates the hypothesis of functional redundancies among individual AOCs due to a lack of phenotypes indicative of JA deficiency (e.g. male sterility). To elucidate whether redundant AOC expression might contribute to regulation on AOC activity level, protein interaction studies using bimolecular fluorescence complementation (BiFC) were performed and showed that all AOCs can interact among each other. The data suggest a putative regulatory mechanism of temporal and spatial fine-tuning in JA formation by differential expression and via possible heteromerization of the four AOCs.
Publications

Sallaud, C.; Giacalone, C.; Töpfer, R.; Goepfert, S.; Bakaher, N.; Rösti, S.; Tissier, A.; Characterization of two genes for the biosynthesis of the labdane diterpene Z-abienol in tobacco (Nicotiana tabacum) glandular trichomes Plant J. 72, 1-17, (2012) DOI: 10.1111/j.1365-313X.2012.05068.x

Leaves of tobacco (Nicotiana tabacum) are covered with glandular trichomes that produce sucrose esters and diterpenoids in varying quantities, depending on cultivar type. The bicyclic diterpene Z‐abienol is the major labdanoid present in some oriental tobacco cultivars, where it constitutes a precursor of important flavours and aromas. We describe here the identification and characterization of two genes governing the biosynthesis of Z‐abienol in N. tabacum. As for other angiosperm labdanoid diterpenes, the biosynthesis of Z‐abienol proceeds in two steps. NtCPS2 encodes a class‐II terpene synthase that synthesizes 8‐hydroxy‐copalyl diphosphate, and NtABS encodes a kaurene synthase‐like (KSL) protein that uses 8‐hydroxy‐copalyl diphosphate to produce Z‐abienol. Phylogenetic analysis indicates that NtABS belongs to a distinct clade of KSL proteins that comprises the recently identified tomato (Solanum habrochaites) santalene and bergamotene synthase. RT‐PCR results show that both genes are preferentially expressed in trichomes. Moreover, microscopy of NtCPS2 promoter‐GUS fusion transgenics demonstrated a high specificity of expression to trichome glandular cells. Ectopic expression of both genes, but not of either one alone, driven by a trichome‐specific promoter in transgenic Nicotiana sylvestris conferred Z‐abienol formation to this species, which does not normally produce it. Furthermore, sequence analysis of over 100 tobacco cultivars revealed polymorphisms in NtCPS2 that lead to a prematurely truncated protein in cultivars lacking Z‐abienol, thus establishing NtCPS2 as a major gene controlling Z‐abienol biosynthesis in tobacco. These results offer new perspectives for tobacco breeding and the metabolic engineering of labdanoid diterpenes, as well as for structure–function relationship studies of terpene synthases.
Publications

Landgraf, R.; Schaarschmidt, S.; Hause, B.; Repeated leaf wounding alters the colonization of Medicago truncatula roots by beneficial and pathogenic microorganisms Plant Cell Environ. 35, 1344-1357, (2012) DOI: 10.1111/j.1365-3040.2012.02495.x

In nature, plants are subject to various stresses that are often accompanied by wounding of the aboveground tissues. As wounding affects plants locally and systemically, we investigated the impact of leaf wounding on interactions of Medicago truncatula with root‐colonizing microorganisms, such as the arbuscular mycorrhizal (AM) fungus Glomus intraradices, the pathogenic oomycete Aphanomyces euteiches and the nitrogen‐fixing bacterium Sinorhizobium meliloti. To obtain a long‐lasting wound response, repeated wounding was performed and resulted in locally and systemically increased jasmonic acid (JA) levels accompanied by the expression of jasmonate‐induced genes, among them the genes encoding allene oxide cyclase 1 (MtAOC1) and a putative cell wall‐bound invertase (cwINV). After repeated wounding, colonization with the AM fungus was increased, suggesting a role of jasmonates as positive regulators of mycorrhization, whereas the interaction with the rhizobacterium was not affected. In contrast, wounded plants appeared to be less susceptible to pathogens which might be caused by JA‐induced defence mechanisms. The effects of wounding on mycorrhization and pathogen infection could be partially mimicked by foliar application of JA. In addition to JA itself, the positive effect on mycorrhization might be mediated by systemically induced cwINV, which was previously shown to exhibit a regulatory function on interaction with AM fungi.
Books and chapters

Walter, M. H.; Floss, D. S.; Paetzold, H.; Manke, K.; Vollrath, J.; Brandt, W.; Strack, D.; Control of Plastidial Isoprenoid Precursor Supply: Divergent 1-Deoxy-D-Xylulose 5-Phosphate Synthase (DXS) Isogenes Regulate the Allocation to Primary or Secondary Metabolism (Bach, T. J. & Rohmer, M., eds.). 251-270, (2012) ISBN: 978-1-4614-4063-5 DOI: 10.1007/978-1-4614-4063-5_17

Following the description of two separate pathways for isoprenoid precursor biosynthesis in plants, a new level of complexity has been introduced by the discovery of two divergent gene classes encoding the first enzyme of the plastidial methylerythritol phosphate (MEP) pathway. These nonredundant 1-deoxy-d-xylulose 5-phosphate synthase (DXS) isogenes are differentially expressed in such a way that DXS1 appears to serve housekeeping functions, whereas DXS2 is associated with the production of specialized (secondary) isoprenoids involved in ecological functions. Examples of the latter are apocarotenoid formation in roots colonized by arbuscular mycorrhizal fungi and mono- or diterpenoid biosynthesis in trichomes. Knockdown of DXS2 genes can specifically suppress secondary isoprenoid formation without affecting basic plant functions. Analyzing DXS isogenes along the progression of land plant evolution shows separation in structure and complementary expression already at the level of gymnosperms, which is maintained in all angiosperms except Arabidopsis.
Books and chapters

Tissier, A.; Trichome Specific Expression: Promoters and Their Applications (Çiftçi, Y. O., ed.). 353-378, (2012) DOI: 10.5772/32101

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Books and chapters

Tissier, A.; Sallaud, C.; Rontein, D.; Tobacco Trichomes as a Platform for Terpenoid Biosynthesis Engineering (Bach, T. J. & Rohmer, M., eds.). 271-283, (2012) ISBN: 978-1-4614-4063-5 DOI: 10.1007/978-1-4614-4063-5_18

Many plant species have evolved specialized organs dedicated to the production of a restricted number of secondary metabolites. These organs have secretory tissues which can lead to very significant accumulations of products, in the range of mg per g of fresh weight. These natural cell factories are therefore interesting targets for metabolic engineering. Plant glandular trichomes in particular have attracted interest because of the relative ease to isolate them and to analyse the compounds they produce because they are secreted onto the leaf surface. Depending on the species, trichomes can produce a variety of metabolites. Terpenoids however are particularly well represented and have been used by humans in a variety of industries, including as aroma, fragrance and pharmaceutical ingredients. Tobacco trichomes produce diterpenoids in large amounts and were therefore chosen as a model system for engineering the biosynthesis of this important class of compounds. We present here our strategy and first results, which bode well for the future of glandular trichomes as engineered natural cellular factories.
Publications

Zdyb, A.; Demchenko, K.; Heumann, J.; Mrosk, C.; Grzeganek, P.; Göbel, C.; Feussner, I.; Pawlowski, K.; Hause, B.; Jasmonate biosynthesis in legume and actinorhizal nodules New Phytol. 189, 568-579, (2011) DOI: 10.1111/j.1469-8137.2010.03504.x

Jasmonic acid (JA) is a plant signalling compound that has been implicated in the regulation of mutualistic symbioses. In order to understand the spatial distribution of JA biosynthetic capacity in nodules of two actinorhizal species, Casaurina glauca and Datisca glomerata, and one legume, Medicago truncatula, we determined the localization of allene oxide cyclase (AOC) which catalyses a committed step in JA biosynthesis. In all nodule types analysed, AOC was detected exclusively in uninfected cells.The levels of JA were compared in the roots and nodules of the three plant species. The nodules and noninoculated roots of the two actinorhizal species, and the root systems of M. truncatula, noninoculated or nodulated with wild‐type Sinorhizobium meliloti or with mutants unable to fix nitrogen, did not show significant differences in JA levels. However, JA levels in all plant organs examined increased significantly on mechanical disturbance.To study whether JA played a regulatory role in the nodules of M. truncatula, composite plants containing roots expressing an MtAOC1‐sense or MtAOC1‐RNAi construct were inoculated with S. meliloti. Neither an increase nor reduction in AOC levels resulted in altered nodule formation.These data suggest that jasmonates are not involved in the development and function of root nodules.
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