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Plants Constitutively (plant + constitutively)
Selected AbstractsGeranyl acetate esterase is commonly present but linalyl acetate esterase occurrence is highly limited in plantsFLAVOUR AND FRAGRANCE JOURNAL, Issue 3 2007Neelam S. Sangwan Abstract Esterases are a group of hydrolytic enzymes that split ester bonds by addition of water and are ubiquitously present in diverse biosystems. Although animal esterases are well studied and are catalytically and functionally classified into different groups, plant enzymes have been viewed rather generally and are casually recruited as biochemical markers in morphogenesis, genetic characterization of plants, etc., without functional emphasis. Some volatile oil plants constitutively synthesize their characteristic monoterpene esters, geranyl acetate and linalyl acetate being the most common among them in the acyclic monoterpene class, whereas other plants also synthesize some volatile hemi- to sesquiterpene esters but inductively under certain ecological situations, such as herbivory, wounding, etc. This study concerns screening relative distribution of geranyl acetate esterase and linalyl aceate esterase activities in selected medicinal and aromatic plants, and reveals that in plants geranyl acetate (a primary alcohol ester) esterase is commonly present, while linalyl acetate (a tertiary alcohol ester) esterase seems to be highly limited to those plants (e.g. Lippia alba, Mentha citrata) that biosynthesize the tertiary monoterpene alcohol linalool and its ester. Such contrasting distribution of the two discrete types of esterases has been discussed in light of scenario of their microbial counterparts and structure,function relationships established thereon. This study makes it obvious that the GGG(A)-X motif esterases (acting on tertiary alcohol esters) are rare entities in plants too, similar to microbes. Furthermore, their presence in some volatile oil plants renders such plants novel phytoresources of the GGGX/GGAX motif hydrolases. Detailed characterization of the motif-specific plant esterases would have an immense impact on understanding of their structure,function relationships in plants. Copyright © 2007 John Wiley & Sons, Ltd. [source] Trade-offs between the shade-avoidance response and plant resistance to herbivores?FUNCTIONAL ECOLOGY, Issue 6 2005Tests with mutant Cucumis sativus Summary 1Plants exhibit adaptations to many stresses, including light competition and herbivory. The expression of these traits may interact negatively, potentially instigating a trade-off. 2We employed a combination of genetically altered Cucumis sativus varieties and phenotypic manipulations to test for trade-offs in field experiments. The different genetic lines of C. sativus were altered in their phytochrome-mediated shade responses and the production of terpenoid defence compounds. 3Cucumber plants constitutively expressing the shade-avoidance response had 93% more herbivory by specialist beetles compared with wild types. The long-hypocotyl mutants also produced leaves with fewer trichomes, greater toughness and a higher carbon to nitrogen ratio (C : N) than wild types. Plants lacking defensive cucurbitacins had 23% longer internodes than the cucurbitacin-producing line. 4We then manipulated the plant phenotype by artificially imposing neighbours' shade on plants with and without cucurbitacins. As expected, plants responded to shade by growing longer hypocotyls and first internodes, but few trade-offs were found between plant line and shade treatment and, although herbivory levels were very low, there was a trend towards reduced damage on shaded plants. 5The use of genetically altered plant lines provided strong evidence for the trade-off hypothesis, while phenotypic manipulations did not support the hypothesis. [source] Cloning and characterization of a Chlamydomonas reinhardtii cDNA arylalkylamine N -acetyltransferase and its use in the genetic engineering of melatonin content in the Micro-Tom tomatoJOURNAL OF PINEAL RESEARCH, Issue 4 2009Masateru Okazaki Abstract:, Melatonin is found in a wide variety of plant species. Several investigators have studied the physiological roles of melatonin in plants. However, its role is not well understood because of the limited information on its biosynthetic pathway. To clarify melatonin biosynthesis in plants, we isolated a cDNA-coded arylalkylamine N -acetyltransferase (AANAT), a possible limiting enzyme for melatonin biosynthesis, from Chlamydomonas reinhardtii (designated as CrAANAT). The predicted amino acid sequence of CrAANAT shares 39.0% homology to AANAT from Ostreococcus tauri and lacks cAMP-dependent protein kinase phosphorylation sites in the N- and C-terminal regions that are conserved in vertebrates. The enzyme activity of CrAANAT was confirmed by in vitro assay using Escherichia coli. Transgenic plants constitutively expressing the CrAANAT were produced using Micro-Tom, a model cultivar of tomato (Solanum lycopersicum L.). The transgenic Micro-Tom exhibited higher melatonin content compared with wild type, suggesting that melatonin was synthesized from serotonin via N -acetylserotonin in plants. Moreover, the melatonin-rich transgenic Micro-Tom can be used to elucidate the role of melatonin in plant development. [source] Systemin-dependent salinity tolerance in tomato: evidence of specific convergence of abiotic and biotic stress responsesPHYSIOLOGIA PLANTARUM, Issue 1 2010Francesco Orsini Plants have evolved complex mechanisms to perceive environmental cues and develop appropriate and coordinated responses to abiotic and biotic stresses. Considerable progress has been made towards a better understanding of the molecular mechanisms of plant response to a single stress. However, the existence of cross-tolerance to different stressors has proved to have great relevance in the control and regulation of organismal adaptation. Evidence for the involvement of the signal peptide systemin and jasmonic acid in wound-induced salt stress adaptation in tomato has been provided. To further unravel the functional link between plant responses to salt stress and mechanical damage, transgenic tomato (Lycopersicon esculentum Mill.) plants constitutively expressing the prosystemin cDNA have been exposed to a moderate salt stress. Prosystemin over-expression caused a reduction in stomatal conductance. However, in response to salt stress, prosystemin transgenic plants maintained a higher stomatal conductance compared with the wild-type control. Leaf concentrations of abscissic acid (ABA) and proline were lower in stressed transgenic plants compared with their wild-type control, implying that either the former perceived a less stressful environment or they adapted more efficiently to it. Consistently, under salt stress, transgenic plants produced a higher biomass, indicating that a constitutive activation of wound responses is advantageous in saline environment. Comparative gene expression profiling of stress-induced genes suggested that the partial stomatal closure was not mediated by ABA and/or components of the ABA signal transduction pathway. Possible cross-talks between genes involved in wounding and osmotic stress adaptation pathways in tomato are discussed. [source] | ||||||||||