Showing papers in "Critical Reviews in Plant Sciences in 2001"
TL;DR: In this article, the entrapment, uptake, and accumulation of heavy metals by lichen thalli, made apparent by parameters of lichen vitality and stress, were investigated by means of controlled experiments.
Abstract: Recent records of environmental contamination noted a moderate decrease of SO2 pollution, whereas the burden of atmospheric heavy metals is still considerable. The present review refers to the entrapment, uptake, and accumulation of heavy metals by lichen thalli, made apparent by parameters of lichen vitality and stress. The particulate nature of airborne heavy metals is made evident by parameters referring to the entrapment of heavy-metal containing particles by lichen thalli. The mechanism of uptake of heavy metals, investigated by means of controlled experiments, refers to extracellular and intracellular uptake. The rate of absorption and the accumulation of heavy metals is dependent on morphological features of lichen thalli in addition to kind and intensity of emission sources and to nonanthropogenic factors such as climate and topography. The role of lichens as biomonitors is demonstrated by the case of lead. In contrast to data obtained by retrospective studies, using lichens as biomonitors of heav...
417 citations
TL;DR: Themes that emerge after consideration of the published data are that glycans and peptide elicitors are likely primary triggers of wound-induced defense responses and that they function through the action of jasmonic acid, a central mediator of defense gene expression, whose effect is modulated by ethylene.
Abstract: Damage inflicted by herbivore feeding necessitates multiple defense strategies in plants. The wound site must be sealed and defense responses mounted against the herbivore itself and against invading opportunistic pathogens. These defenses are controlled both in time and space by highly complex regulatory networks that themselves are modulated by interactions with other signaling pathways. In this review, we describe the signaling events that occur in individual wounded leaves, in systemic unwounded regions of the plant, and between the plant, and other organisms, and attempt to place these events in the context of a coordinated system. Key signals that are discussed include ion fluxes, active oxygen species, protein phosphorylation cascades, the plant hormones jasmonic acid, ethylene, abscisic acid and salicylic acid, peptide signals, glycans, volatile chemicals, and physical signals such as hydraulic and electrical signals. Themes that emerge after consideration of the published data are that glycans and peptide elicitors are likely primary triggers of wound-induced defense responses and that they function through the action of jasmonic acid, a central mediator of defense gene expression, whose effect is modulated by ethylene. In the field, wound signaling pathways are significantly impacted on by other stress response pathways, including pathogen responses that often operate through potentially antagonistic signals such as salicylic acid. However, gross generalisations are not possible because some wound and pathogen responses operate through common jasmonate- and ethylene-dependent pathways. Understanding the ways in which local and systemic wound signaling pathways are coordinated individually and in the context of the plants wider environment is a key challenge in the application of this science to crop-protection strategies.
168 citations
TL;DR: Research on improving the forage digestibility of switchgrass, Panicum virgatum L., and other herbaceous species has demonstrated that genetic improvements can be made in forage quality that can have significant economic value.
Abstract: Referee: Dr. E. Charles Brummer, Forage Breeding and Genetics, 1204 Agromonomy, Iowa State University, Ames, IA 50011 Much of the research on the genetic modification of herbaceous plant cell walls has been conducted to improve the utilization of forages by ruminant livestock. The rumen of these animals is basically an anaerobic fermentation vat in which the micro flora break down the complex polysaccharides of plant cell walls into simpler compounds that can be further digested and absorbed by the mammalian digestive system. Research on improving the forage digestibility of switchgrass, Panicum virgatum L., and other herbaceous species has demonstrated that genetic improvements can be made in forage quality that can have significant economic value. To meet future energy needs, herbaceous biomass will need to be converted into a liquid fuel, probably ethanol, via conversion technologies still under development. If feedstock quality can be genetically improved, the economics and efficiency of the conversio...
167 citations
TL;DR: Hall et al. as mentioned in this paper presented a comprehensive case study of biofuel production from maize or corn and evaluated it critically in this review, concluding that the biofuel option on a large scale is not a viable alternative based on economic, energy and eMergy (amount of available energy [exergy] of one form [usually solar] that is directly or indirectly required to provide a given flow or storage of exergy or matter).
Abstract: Referee: Dr. Charles A. S. Hall, Department of Environmental Studies, State University of New York, College of Environmental Science and Forestry, 1 Forestry Drive, Syracuse, NY 13210 Biofuel production systems are sometimes claimed to be able to fill in for future fossil fuel shortages as well as to decrease carbon dioxide emissions and global warming. As such, they are often promoted as a “green” alternative to fossil fuels. I present a comprehensive, system-based case study of biofuel production from maize or corn (Zea mays L.) and evaluate it critically in this review. The case study is taken as an example of the comprehensive approach that I suggest for any energy crop. I conclude that the biofuel option on a large scale is not a viable alternative based on economic, energy and eMergy (amount of available energy [exergy] of one form [usually solar] that is directly or indirectly required to provide a given flow or storage of exergy or matter) analyses of the case study data and estimated possible imp...
164 citations
TL;DR: The role of RIPs in plants is revisited with the emphasis on protection against plant-eating organisms and viruses and the discovery of a novel class of enzymes that use ribosomes damaged by RIPs as a substrate and may act cooperatively with RIPs.
Abstract: Many plants contain proteins that are commonly designated as ribosome-inactivating proteins (RIPs). Based on the structure of the genes and the mature proteins a novel system is proposed to unambiguously classify all RIPs in type-1, type-2, and type-3 RIPs. In addition, the concept of one- and two-chain type-1 RIPs is introduced. After an overview of the occurrence, molecular structure, and amino acid sequences of RIPs, the formation of the mature proteins from the primary translation products of the corresponding mRNAs is elaborated in detail in a section dealing with the biosynthesis, posttranslational modifications, topogenesis, and subcellular location of the different types of RIPs. Details about the three-dimensional structure of type-1 RIPs and the A and B chains of type-2 RIPs are discussed in a separate section. Based on the data given in the previous sections, the phylogenic and molecular evolution of RIPs is critically assessed and a novel model is proposed for the molecular evolution ...
125 citations
TL;DR: The architecture and ontogeny of motile male gametes among major groups of land plants and the utility of spermatogenesis as an informative system in approaching fundamental questions relating to cellular differentiation and motility are examined.
Abstract: Referee: Professor Jeffrey Duckett, School of Biological Sciences, Queen Mary and Westfield College, University of London, Mile End Road, London, E1 4NS, UK Spermatogenesis is a morphogenetic system in plants that is unparalled in its potential to yield diverse and informative structural and developmental data. The unquestionable homology of terrestrial plant spermatozoids to each other and to gametes of related lineages allows an examination of cellular evolution and provides sound data for phylogenetic analyses. In this review we examine the architecture and ontogeny of motile male gametes among major groups of land plants. We begin with a historical perspective that emphasizes the utility of spermatogenesis in understanding cellular evolution and in determining phylogenetic relationships. A cladistic analysis of data based solely on spermatogenesis and a conceptual phylogeny based on combined morphological and molecular data serve as the basis for the comprehensive discussion of architectural and devel...
125 citations
TL;DR: The studies suggest that the mechanisms of intron recognition in plants are likely to differ from yeast and animals and involve novel proteins that recognize the plant-specific cis-elements.
Abstract: Referee: Dr. Gabor Lazar, Chief, Dept. of Molecular Biology, Massachsetts General Hospital, Harvard Medical School, Wellman Eleven, Boston, MA 02114 The coding regions of about 80% of plant nuclear genes contain one or more noncoding intervening sequences (introns). The transcription of these genes results in a precursor mRNA (pre-mRNA) with coding sequences (exons) and introns. The noncoding intervening sequences are then accurately removed and the coding regions are joined in the nucleus to generate functional mRNAs by a process called pre-mRNA splicing. In addition to basic/constitutive splicing, many plant pre-mRNAs, like metazoan pre-mRNAs, undergo alternative splicing, thereby contributing to proteomic complexity. The splicing of pre-mRNAs takes place in a large RNA-protein complex named the spliceosome, which is made up of several small nuclear ribonucleoprotein (snRNP) particles and other associated proteins. Until recently, it was thought that there is only one type of spliceosome in all eukaryot...
101 citations
TL;DR: For some commonly used forage and turf species, significant advances have been achieved in the following areas: (1) establishment of a tissue culture basis for the efficient regeneration of fertile and genetically stable plants, (2) generation of...
Abstract: Referee: Dr. Ian Ray, Plant Breeding and Genetics, Department of Agronomy & Horticulture, New Mexico State University, MSC 3Q, P.O. Box 30003, Las Cruces, NM 88003-8003 Forage and turf grasses are the backbone of sustainable agriculture and contribute extensively to the world economy. They play a major role in providing high quality and economical meat, milk, and fiber products and are important in soil conservation, environmental protection, and outdoor recreation. Conventional breeding contributed substantially to the genetic improvement of forage and turf grasses in the last century. The relatively new developments in genetic manipulation of these species open up opportunities for incorporating cellular and molecular techniques into grass improvement programs. For some commonly used forage and turf species, significant advances have been achieved in the following areas: (1) establishment of a tissue culture basis for the efficient regeneration of fertile and genetically stable plants, (2) generation of...
97 citations
TL;DR: Until effective marker-aided breeding technologies become available, the most promising approach for enhancing ethanol fuel and fiber production and process is to rely on conventional breeding methods for short-rotation poplars.
Abstract: Opportunities for matching wood chemical and physical properties to manufacturing and product requirements via genetic modification have long been recognized Exploitation is now feasible due to advances in trait measurement, breeding, genetic mapping and marker, and genetic transformation technologies With respect to classic selection and breeding of short-rotation poplars, genetic parameters are favorable for decreasing lignin content and increasing specific gravity, but less so for increasing cellulose content Knowledge of functional genomics is expanding, as is that needed for eventual application of marker-aided breeding, trait dissection, candidate gene identification, and gene isolation Research on gene transfer has yielded transgenic poplars with decreased lignin and increased cellulose contents, but otherwise normal growth and development Until effective marker-aided breeding technologies become available, the most promising approach for enhancing ethanol fuel and fiber production and process
53 citations
TL;DR: McLeod et al. as discussed by the authors developed a double cropping system to meet the obligations in the field of environmental protection, which includes a diverse array of crops and provides the opportunity to integrate rural organic wastes into this energy concept.
Abstract: Referee: Dr. J. Grant McLeod, Semiarid Prairie Agricultural Research Centre, Research Branch, Agriculture and Agri-Food Canada, P.O. Box 1030 Swift Current, Saskatchewan S9H 3X2, Canada According to the European Union, biomass will play a major role in the substitution of fossil fuels with renewable resources. Biomass will contribute 83% to the increased use of renewable resources by the year 2010. In contrast to other solar energy sources, plant biomass is always available and can be converted into energy continuously. An important objective in the production of energy crops on arable farm land should be to realize a high net energy yield and fulfill obligations in the field of environmental protection. The “double cropping system” was developed to meet these obligations. Silaging as a conservation method for wet biomass makes this sustainable cultivation system possible. It includes a diverse array of crops and provides the opportunity to integrate rural organic wastes into this energy concept. The mode...
52 citations
TL;DR: This work reviews evidence for the phenotypic plasticity of sylleptic branches and its genetic, environmental, and developmental control, and discusses some trees with the indeterminant growth habit.
Abstract: The crown of many trees is composed of a main axis and branches. All branches arise from axillary or lateral buds and two types of branches exist: proleptic and sylleptic. Proleptic branches form from buds that have undergone a rest period, typically associated with winter dormancy, whereas sylleptic branches emerge without a rest and without complete bud formation. All trees have proleptic branches; some trees with the indeterminant growth habit have both proleptic and sylleptic branches. Sylleptic branches may play an important role in determining tree growth, architecture and adaptation for many temperate-zone woody plants. We review evidence for the phenotypic plasticity of sylleptic branches and its genetic, environmental, and developmental control.
TL;DR: This review investigates the evidence from the published literature for the prevalence of the transfer of superfluous DNA sequences to plant genomes during transformation processes and highlights methods to limit or prevent DNA transfer and subsequent potentially detrimental evolutionary consequences.
Abstract: Referee: Dr. Paul Hooykass, Institut of Molecular Plant Sciences, Leiden University, Clusius Laboratory, Wassenaarseweg 64, 2333, Al Leiden, Netherlands Recent reports suggest the transfer of superfluous DNA sequences to plant genomes during transformation processes. This review investigates the evidence from the published literature for the prevalence of this phenomenon and highlights methods to limit or prevent DNA transfer and subsequent potentially detrimental evolutionary consequences. Evidence for superfluous foreign DNA transfer using both Agrobacterium-mediated transformation and direct DNA transfer methods such as microprojectile bombardment and PEG-mediated transformation of protoplasts is reported. In the case of Agrobacterium-mediated transformation, the lack of information on the integration of sequences from outside of the T-DNA borders has been due to the general belief by researchers that T-DNA processing is precise. This assumption was based on analysis of T-DNA in tumors and as a result ...
TL;DR: Specific recognition of Nod factors by host plants and early stages of signal transduction are discussed.
Abstract: Referee: Dr. Gary Stacey, Director, Center for Legume Research, Department of Microbiology, M409 Walters Life Science Bldg., University of Tennessee, Knoxville, TN 37966-0845 Soil bacteria belonging to genera Rhizobium, Bradyrhizobium, Allorhizobium, Azorhizobium, Mesorhizobium, and Sinorhizobium are able to induce nodule formation on the roots of leguminous plants. In the differentiated root nodules bacteria fix as bacteroids atmospheric nitrogen and deliver it to the host plant. The interaction between bacteria and host plant starts with a complex signal exchange. After induction by plant flavonoids, rhizobia synthesize and secrete lipo-chitooligosaccharides (LCOs), known as Nod factors, which induce morphological changes and expression of early nodulin genes in the roots of host plants. Specific recognition of Nod factors by host plants and early stages of signal transduction are discussed.
TL;DR: What is known about the bacterial, yeast, and plant Hsp100/Clp proteins, their possible relationship, and, more importantly, the cellular roles that this important family of proteins plays in plants are presented.
Abstract: Hsp100/Clp family of proteins is ubiquitously distributed in living systems. Detailed work carried out in bacterial and yeast cells has shown that regulatory members of the Clp family (mainly ClpA, ClpB, and ClpC), together with the catalytic subunit (mainly ClpP), comprise an ATP-dependent two-component proteolytic system. Members of the Hsp100/Clp protein family are not only involved in the regulation of energy-dependent protein hydrolysis but also function as molecular chaperones. However, the biochemical/physiological role(s) of the Hsp100/Clp protein family in higher plants has yet to be elucidated. Recently, this protein family has been implicated in plant stress responses: the hot1 mutant of Arabidopsis thaliana, which has mutation in hsp101 gene, and is defective in tolerance to high temperature (S.-W. Hong and E. Vierling, 2000, Proc Natl Acad Sci USA, 97 (8), 4392-4397) and the transgenic Arabidopsis thaliana plants overexpressing AtHsp101 gene exhibit high temperature tolerance (C. Quietsch et al., 2000, Plant Cell, 12, 479-492). Furthermore, the Hsp101 protein is involved in the translational regulation of cellular mRNAs and one such candidate has been identified as the photosynthetic electron transport gene Ferredoxin 1 mRNA (J. Ling et al., 2000, Plant Cell, 12, 1213-1227). We present what is known about the bacterial, yeast, and plant Hsp100/Clp proteins, discuss their possible relationship, and, more importantly, examine the cellular roles that this important family of proteins plays in plants.
TL;DR: The use of molecular markers in plant breeding has become very commonplace and has given rise to “molecular breeding”.
Abstract: Markers are of interest to plant breeders as a source of genetic information on crops and for use in indirect selection of traits to which the markers are linked. In the classic breeding approach, the markers were invariably the visible morphological and other phenotypic characters, and the breeders expended considerable effort and time in refining the crosses as the tight linkage or association of the desired characters with the obvious phenotypic characters was never unequivocally established. Furthermore, indirect selection for a trait using such morphological markers was not practical due to (1) a paucity of suitable markers, (2) the undesirable pleiotropic effects of many morphological markers on plant phenotype, and (3) the inability to score multiple morphological mutant traits in a single segregating population. With the advancement in molecular biology, the use of molecular markers in plant breeding has become very commonplace and has given rise to “molecular breeding”. Molecular breeding involve...
TL;DR: The analysis of microrganism motors and motor controlling devices such as flagella and their accessory components suggests that the movement of these structures can be considered an example of propagation of sensory information along lattice-like structures by means of repetitive protein conformational changes.
Abstract: Referee: Dr. Kenneth R. Robinson, Department of Biological Sciences, Purdue University, West Lafayette, IN 47907-1392 Crawling, sliding, and swimming are only a few of the many motile responses of ...