Showing papers on "Biotic stress published in 2003"

Understanding plant responses to drought — from genes to the whole plant

Abstract: In the last decade, our understanding of the processes underlying plant response to drought, at the molecular and whole-plant levels, has rapidly progressed. Here, we review that progress. We draw attention to the perception and signalling processes (chemical and hydraulic) of water deficits. Knowledge of these processes is essential for a holistic understanding of plant resistance to stress, which is needed to improve crop management and breeding techniques. Hundreds of genes that are induced under drought have been identified. A range of tools, from gene expression patterns to the use of transgenic plants, is being used to study the specific function of these genes and their role in plant acclimation or adaptation to water deficit. However, because plant responses to stress are complex, the functions of many of the genes are still unknown. Many of the traits that explain plant adaptation to drought - such as phenology, root size and depth, hydraulic conductivity and the storage of reserves - are those associated with plant development and structure, and are constitutive rather than stress induced. But a large part of plant resistance to drought is the ability to get rid of excess radiation, a concomitant stress under natural conditions. The nature of the mechanisms responsible for leaf photoprotection, especially those related to thermal dissipation, and oxidative stress are being actively researched. The new tools that operate at molecular, plant and ecosystem levels are revolutionising our understanding of plant response to drought, and our ability to monitor it. Techniques such as genome-wide tools, proteomics, stable isotopes and thermal or fluorescence imaging may allow the genotype-phenotype gap to be bridged, which is essential for faster progress in stress biology research.

Plant responses to drought, salinity and extreme temperatures: towards genetic engineering for stress tolerance

Abstract: Abiotic stresses, such as drought, salinity, extreme temperatures, chemical toxicity and oxidative stress are serious threats to agriculture and the natural status of the environment. Increased salinization of arable land is expected to have devastating global effects, resulting in 30% land loss within the next 25 years, and up to 50% by the year 2050. Therefore, breeding for drought and salinity stress tolerance in crop plants (for food supply) and in forest trees (a central component of the global ecosystem) should be given high research priority in plant biotechnology programs. Molecular control mechanisms for abiotic stress tolerance are based on the activation and regulation of specific stress-related genes. These genes are involved in the whole sequence of stress responses, such as signaling, transcriptional control, protection of membranes and proteins, and free-radical and toxic-compound scavenging. Recently, research into the molecular mechanisms of stress responses has started to bear fruit and, in parallel, genetic modification of stress tolerance has also shown promising results that may ultimately apply to agriculturally and ecologically important plants. The present review summarizes the recent advances in elucidating stress-response mechanisms and their biotechnological applications. Emphasis is placed on transgenic plants that have been engineered based on different stress-response mechanisms. The review examines the following aspects: regulatory controls, metabolite engineering, ion transport, antioxidants and detoxification, late embryogenesis abundant (LEA) and heat-shock proteins.

Molecular genetic perspectives on cross‐talk and specificity in abiotic stress signalling in plants

Abstract: The perception of abiotic stresses and signal transduction to switch on adaptive responses are critical steps in determining the survival and reproduction of plants exposed to adverse environments. Plants have stress-specific adaptive responses as well as responses which protect the plants from more than one environmental stress. There are multiple stress perception and signalling pathways, some of which are specific, but others may cross-talk at various steps. Recently, progress has been made in identifying components of signalling pathways involved in salt, drought and cold stresses. Genetic analysis has defined the Salt-Overly-Sensitive (SOS) pathway, in which a salt stress-induced calcium signal is probably sensed by the calcium-binding protein SOS3 which then activates the protein kinase SOS2. The SOS3‐SOS2 kinase complex regulates the expression and activity of ion transporters such as SOS1 to reestablish cellular ionic homeostasis under salinity. The ICE1 (Inducer of CBF Expression 1)‐CBF (CRepeat Binding Protein) pathway is critical for the regulation of the cold-responsive transcriptome and acquired freezing tolerance, although at present the signalling events that activate the ICE1 transcription factor during cold stress are not known. Both ABAdependent and -independent signalling pathways appear to be involved in osmotic stress tolerance. Components of mitogen-activated protein kinase (MAPK) cascades may act as converging points of multiple abiotic as well as biotic stress signalling pathways. Forward and reverse genetic analysis in combination with expression profiling will continue to uncover many signalling components, and biochemical characterization of the signalling complexes will be required to determine specificity and crosstalk in abiotic stress signalling pathways.

Ethylene and jasmonic acid signaling affect the NPR1-independent expression of defense genes without impacting resistance to Pseudomonas syringae and Peronospora parasitica in the Arabidopsis ssi1 mutant.

Abstract: Salicylic acid (SA), ethylene, and jasmonic acid (JA) are important signaling molecules in plant defense to biotic stress. An intricate signaling network involving SA, ethylene, and JA fine tunes plant defense responses. SA-dependent defense responses in Arabidopsis thaliana are mediated through NPR1-dependent and -independent mechanisms. We have previously shown that activation of an NPR1-independent defense mechanism confers enhanced disease resistance and constitutive expression of the pathogenesis-related (PR) genes in the Arabidopsis ssi1 mutant. In addition, the ssi1 mutant constitutively expresses the defensin gene PDF1.2. Moreover, SA is required for the ssi1-conferred constitutive expression of PDF1.2 in addition to PR genes. Hence, the ssi1 mutant appears to target a step common to SA- and ethylene- or JA-regulated defense pathways. In the present study, we show that, in addition to SA, ethylene and JA signaling also are required for the ssi1-conferred constitutive expression of PDF1.2 and the NPR1-independent expression of PR-1. Furthermore, the ethylene-insensitive ein2 and JA-insensitive jar1 mutants enhance susceptibility of ssi1 plants to the necrotrophic fungus Botrytis cinerea. However, defects in either the ethylene- or JA-signaling pathways do not compromise ssi1-conferred resistance to the bacterial pathogen Pseudomonas synringae pv. maculicola and the oomycete pathogen Peronospora parasitica. Interestingly, ssi1 exhibits a marginal increase in the levels of ethylene and JA, suggesting that low endogenous levels of these phytohormones are sufficient to activate expression of defense genes. Taken together, our results indicate that although cross talk in ssi1 renders expression of ethylene- or JA-responsive defense genes sensitive to SA and vice versa, it does not affect downstream signaling leading to resistance.

From plant tissue culture to biotechnology: Scientific revolutions, abiotic stress tolerance, and forestry

Abstract: Plant biotechnology—especially in vitro regeneration and cell biology, DNA manipulation and biochemical engineering—is already changing the agricultural scene in three major areas: control of plant growth, protecting plants against biotic stress, and production of specialty foods, biochemicals and pharmaceuticals. Plant biotechnology faces several major challenges in the coming decades: alleviating the hazards of abiotic stress (especially salinity, drought, and extreme temperatures), improving pest control, maintenance and improvement of the environment, improvement of food quality and design of ‘specialty food’ using biochemical engineering, and production of biomaterials. Two parallel research approaches will most likely exist simultaneously in the near future: the transgenic approach (expression of unique genes and specific promoters and transcription factors), and the non-transgenic approach (genomics-assisted gene discovery, marker-assisted selection, efficient mutations, and clonal agriculture). Drought and salinity are the most serious threats to agriculture and to the environment in many parts of the world. Key molecular factors that are being used for genetic engineering of stress-tolerant plants include: over-expression of specific transcription factors, characterization of dehydrin proteins, over-production of osmoprotectants, expression of water channel proteins and ion transporters, expression and characterization of molecular chaperones, including a novel boiling-stable homo-oligomeric SP1 protein. Although molecular breeding is routine in agriculture, forest-tree species have been left far behind. However, the increasing demand for wood and its products and the reduction of available harvestable forests has recently led to the introduction of several molecular and biotechnological tools into forest-tree research and improvement. Among these are in vitro propagation, the identification of molecular markers, and genetic engineering for specific traits. Achievements today in plant biotechnology have already surpassed all previous expectations. The full realization and impact of the new developments depend not only on continued successful and innovative research and development activities, but also on a favorable regulatory climate and public acceptance. Plant scientists now have a central role in society.

Volatiles emitted from in vitro grown tomato shoots during abiotic and biotic stress

Abstract: Different stress factors were applied to in vitro grown tomato shoots (Lycopersicon esculentum Mill. `Moneymaker') to investigate the volatiles released in the headspace. Solid phase microextraction was used for the experiments with an abiotic stress factor (constant light) and automated dynamic sampling was used for the experiments with a biotic stress factor (Spodoptera littoralis caterpillar). Continuous light as stress factor induced constant emission of the sesquiterpene a-copaene. Constant emission was not found with any other sesquiterpene or with monoterpenes. Therefore, we hypothesize that this compound needs light for its biosynthesis and/ or emission. An attack by caterpillars caused an immediate higher emission of the constitutive compounds (mono-and sesquiterpenes) and the induced compounds (linalool and indole); the latter were emitted approximately 1 day after the attack and linalool was even emitted 2 days after removal of the caterpillar.

Transcripts of sunflower antioxidant scavengers of the SOD and GPX families accumulate differentially in response to downy mildew infection, phytohormones, reactive oxygen species, nitric oxide, protein kinase and phosphatase inhibitors

Abstract: Messenger RNA accumulation of two previously characterized sunflower glutathione peroxidases (GPXha-1 and GPXha-2) was monitored in response to pathogen attack. The accumulation of GPXha-1 and GPXha-2 mRNAs was also followed after stimulation with various signalling molecules including stress related phytohormones, reactive oxygen species, nitric oxide and protein phosphatase or kinase inhibitors. To have a more complete view of the response of the plant enzymatic antioxidant system when challenged by these various stimuli, the accumulation of superoxide dismutase (SOD) mRNAs was monitored too. To do so, partial sunflower SOD cDNAs (SODha-1 and SODha-2) were cloned in the course of the study. We show here that sunflower GPX mRNA accumulated differently in leaves of plants infected with either a virulent or an avirulent race of pathogen (Plasmopara halstedii). We also observed that any of the stimuli used translated in a stronger accumulation of both GPX mRNAs. These data suggest that GPX enzymes are involved in the hypersensitive and stress responses in sunflower. When compared to each other, GPX and SOD messenger steady state levels behaved differently following biotic stress or treatments with stress signalling factors. This suggests that the antioxidant enzymes GPX and SOD are likely to play different functions in stress responses.

Phoenix clones: recovery after long-term defoliation- induced dormancy

Abstract: Many long-lived plants are known to prolong dormancy in response to abiotic stresses such as drought. We are unaware, however, of any reports of plants prolonging dormancy in response to biotic stresses such as herbivory. We monitored 140 putative Solidago missouriensis clones (hereafter ‘clones’) ≥ 13 years before, during and after intense defoliation by the specialist herbivore Trirhabda canadensis. Eight of the clones produced no above-ground growth in the season following defoliation. Though apparently killed, these clones reappeared 1–10 years after they disappeared, with six of them robustly recovering in a single season. We used 38 RAPD markers to test the hypotheses (denoted by H and numbered with subscripts) that territories were recovered by (H1) seedling establishment or (H2) rhizomes. We compared pre-defoliation and post-recovery genotypes in two clones using the same 38 markers. Our data document the existence of very large clones (60–350 m2 with c. 700–20 000 ramets), and support the hypothesis that recovery is from rhizomes. Within-clone diversity is low, and the pre-defoliation and post-recovery genotypes match. We consider mechanisms that could enable plants entering dormancy with depleted resources to robustly recover, and the implications of dormancy for avoiding biotic stress such as that induced by T. canadensis.

Chapter 9 Diversity in abiotic stress tolerances

Abstract: Abiotic stress is responsible for significant yield losses in barley on a worldwide scale, and yet under severe stress conditions, barley is one of the most important sources of energy for human food and animal feed. All evidence indicates that abiotic stress tolerance in barley is a complex trait largely under polygenic control. Further, more thorough investigations are necessary to elucidate the basic metabolic processes involved in the plant response and their genetic control when insulted by single or multiple stresses. The knowledge derived from this research represents a milestone for developing new strategies for a better use of barley biodiversity to improve this crop species and to use it as a model plant. For this purpose, new barley variability, and "new mutants," are required to amplify the spectrum of specific morphological and physiological traits. For all these reasons, it is essential to improve the evaluation for abiotic stress resistance of genetic resources conserved ex situ, and to maintain and promote the in situ conservation to ensure the germplasm can cope with stress conditions.

Signal Molecules for Plant Defense Responses to Biotic Stress

Abstract: Plants are capable of recognizing the penetrating pathogens and of responding to their attack by the activation of the defense systems. Signal transduction from the receptor to the cell genome is required for this activation. Recently, signal molecules have been found, which are involved in the signal transduction triggered in response to biotic stress. The data accumulated imply the presence of a complex and well-coordinated signal network in plant cells. This net controls plant defense responses to pathogen attacks.

Hormones are in the air.

Abstract: Phytohormones act to control many aspects of plant growth, development, and responses to the environment. Genetic and biochemical studies have identified many of the factors that mediate hormonal control of cell division, expansion, differentiation, and, ultimately, death. However, despite major advances in our understanding of how individual hormones act, we know relatively little about how hormonal signals are integrated into overall responses. For example, the hormones indole-3-acetic acid (IAA), gibberellin (GA), brassinolide, and, in some circumstances, ethylene all promote stem elongation. But what is the role of each hormone, and how do they interact to mediate growth? An abundance of hormone-related mutants, particularly in Arabidopsis , has provided some insights into the mechanisms of cooperative hormone action. Note that the term “cross-talk” is frequently used in this context. However, classically, this term defines phenomena in which there is an unwanted transfer of signals from one circuit, channel, etc., to another (Oxford English Dictionary). These interactions are most certainly not “unwanted.” In a narrower context, crosstalk is generally limited to common elements within a signal transduction scheme. Such a definition clearly ignores a major source of phytohormone interactions: effects of one input signal on accumulation of other input signals. For example, genetic analyses have defined a complex relationship among sugars, abscisic acid (ABA), and ethylene (1, 2) that controls aspects of growth and development. This interaction is regulated at the level of both hormone synthesis and signal transduction. However, the molecular details of this and other interactions are far from understood. Some of the best characterized examples of the complex interactions between phytohormones involve responses to biotic stress. For example, wound responses, such as those induced by chewing insects, integrate jasmonic acid (JA), ethylene, and systemin signaling pathways in a manner yet to be fully established (3, 4). Similarly, …

Photosynthetic Pigments of Tomato Plants under Conditions of Biotic Stress and Effects of Furostanol Glycosides

Abstract: The adaptogenic effect of furostanol glycosides (FG) on biosynthesis of photosynthetic pigments in tomato plants (Lycopersicon esculentum Mill.) was studied under conditions of biotic stress caused by root-knot nematode (Meloidogyne incognita Kofoid et White). Treatment of plants with 5 × 10–4 M FG was accompanied by an increase in the rate of biosynthesis of pigments (particularly, chlorophyll b and carotenoids), which was observed against the background of a decrease in the relative contribution of β-carotene and an increase in the relative contribution of pigments of the violaxanthin cycle (VXC) to the overall pool of carotenoids. It was suggested that FG stimulated phytoimmunity by shifting metabolism of carotenoids toward enhanced biosynthesis of VXC pigments. These pigments play a protective role and facilitate stabilization of the photosynthetic apparatus, which is particularly important under stress conditions.

A new partner in the danse macabre: the role of nitric oxide in the hypersensitive response

Abstract: Summary. Plant responses to abiotic and biotic stress are to a great extent coordinated by similar chemical signals. Thus, salicylic acid (SA) and reactive oxygen intermediates (ROIs) influence tolerance to heat and chilling as much as resistance to pathogens during the hypersensitive response (HR) form of cell death. We have shown that following elicitation the generation of SA and ROI is biphasic and each signal influences the production of the other in a positive feedback mechanism. When SA is applied alone this “potentiates” plant responses to be more effective following elicitation by either pathogenic challenge or abiotic stress. Nitric oxide (NO) has also been proposed to contribute towards plant defence. Using photoacoustic laser (PLA) detection NO generation was detected in tobacco following challenge with bacterial pathogens but was not produced in a biphasic manner. In contrast PLA measurements showed that C 2 H 4 production during the HR was biphasic. This pattern of C2H4 production could be mimicked with the NO-donor sodium nitroprusside (SNP), acting part through the initiation of SA synthesis. A model is proposed where NO acts with SA to influence the biphasic production of cell death-eliciting signals including ROI and C2H4.

Carbohydrates and resistance to Phytophthora infestans in potato plants

Abstract: Plants generally deal with biotic or abiotic stresses by altering components as for example cell wall constituents and metabolites. Infection by Phytophthora infestans, the causal agent of late blight, constitutes a stress condition for the plants and they react to it with changes arising in their metabolism depending on the resistance level of the plants. The present work compares two potato hybrids differing in their level of horizontal resistance to late blight. Carbohydrate content in stems and leaves of infected and uninfected plants was determined by HPLC. Some carbohydrates accumulated in the stems of the resistant hybrid infected by P. infestans, whereas they remained unchanged in the susceptible hybrid. On the other hand, in the leaves, these carbohydrates accumulated only in the infected susceptible hybrid.

The Competitiveness of Pseudomonas chlororaphis Carrying pJP4 Is Reduced in the Arabidopsis thaliana Rhizosphere

Abstract: The effect of the large catabolic IncP plasmid pJP4 on the competitiveness of Pseudomonas chlororaphis SPR044 and on its derivatives SPR244 (GacS deficient), SPR344 (phenazine-1-carboxamide overproducer), and SPR644 (phenazine-1-carboxamide deficient) in the Arabidopsis thaliana rhizosphere was assessed. Solitary rhizosphere colonization by the wild type, SPR244, and SPR644 was not affected by the plasmid. The size of the population of SPR344 carrying pJP4, however, was significantly reduced compared to the size of the population of the plasmid-free derivative. The abiotic stress caused by phenazine-1-carboxamide overproduction probably resulted in a selective disadvantage for cells carrying pJP4. Next, the effect of biotic stress caused by coinoculation of other bacteria was analyzed. Cells carrying pJP4 had a selective disadvantage compared to plasmid-free cells in the presence of the efficient colonizer Pseudomonas fluorescens WCS417r. This effect was not observed after coinoculation with a variety of other bacteria, and it was independent of quorum sensing and phenazine-1-carboxamide production. Thus, the presence of large catabolic plasmids imposes a detectable metabolic burden in the presence of biotic stress. Plasmid transfer in the A. thaliana rhizosphere from P. chlororaphis and its derivatives to Ralstonia eutropha was determined by using culture-dependent and culture-independent techniques. With the cultivation-independent technique we detected a significantly higher portion of exconjugants, but pJP4 transfer was independent of the quorum-sensing system and of phenazine-1-carboxamide production.

Physiological characters imparting resistance to biotic and abiotic stresses in sugarcane

Abstract: Sugarcane genotypes have been known to possess differential resistance to biotic and abiotic stresses which adversely affect sugarcane and sugar productivityper se. This review is an effort to elucidate physiological characteristics imparting resistance/ tolerance to biotic stressesviz. insect-pests and diseases and abiotic stresses, viz. drought, waterlogging,etc. Certain physiological attributes like tight leaf sheaths imparted multiple resistance,i.e., against internode borer, pyrilla and Iygaeid bugs; aged canes imparted resistance to mealy bugs, eye spot and rust diseases and waterlogged conditions. Similarly, polyphenol oxidase activity related to resistance against red rot and waterlogged conditions. Resistance to certain stresses is also confounded with a number of other morphological or physiological characteristics. These characteristics could be considered as physiological basis for resistance to biotic and abiotic stresses and also used as marker for marker-assisted selection in directed breeding programmes.

Effect of biotic stress (aspergillus niger) on the production and accumulation of total alkaloids in atropa belladonna l. via tissue culture

Abstract: An efficient protocol for enhancement of total alkaloids production from suspension cultures of A. belladonna L. was established. The effect of MS-medium supplemented with different concentrations of naphthalene acetic acid (NAA) and benzyl adenine (BA) on growth parameters as well as total alkaloid production was investigated. In the same connection, the effect of biotic stress caused by various concentrations of Aspergillus niger on alkaloid accumulation and production was investigated. The optimum values of cell growth parameters and alkaloid production were obtained for leaf, stem and root cell cultures, respectively. The optimum supplementation of liquid MS-medium was 1 mg/l of each of NAA and BA. A. niger extract at 10 % (~ 0.5 mg/ mL) gave the highest value for cell growth and alkaloid accumulation in the different types of cell cultures following 10 days of cultivation. Total alkaloid contents of different cell cultures were identified by HPLC. INTRODUCTION Plant secondary products are used extensively in commerce, particularly in the food and pharmaceutical industries, and many of these compounds have proved to be target compounds for plant cell culture production. There have been a number of excellent publications on this topic within the last decade. Plant cell cultures have the capability of producing a wide range of secondary compounds (Phillipson, 1990). Atropa belladonna L. (Solanaceae) is one of the most important medicinal plants and is a source of tropane alkaloids such as hyoscyamine and scopolamine. Medicinally, A. belladonna is used for the use of its alkaloids in the treatment of Parkinson’s disease for its anti-inflammatory properties, for relief of bronchial asthma and motion sickness and its ability to counteract toxic agents. Belladonna extract is used as an antimuscarinic agent, which accounts for its use as a spasmolytic drug. Also, it is used as a concomitant therapy in the treatment of peptic ulcer and functional digestive disorders, including spastic, mucous, and pancreatitis. Plant growth regulators and nutritional factors affect the production of secondary metabolites, as well as growth, of cell cultures of higher plants (Sakuta and Komamine, 1987; Szoke et al., 1982, 1992; Vida et al., 2000; Laszlo et al., 2001). Also, types and concentrations of growth regulators affect secondary product formation (Bohm, 1980; Krajewska et al., 1987; Bálványos et al., 2001). The presence of 2,4-dichlorophenoxy acetic acid (2,4-D), indole acetic acid (IAA) and (NAA) increased the production of indole alkaloids in cell cultures of Cinchona ledgeriana (Harkes et al, 1985). Moreover, Nussbaumer et al., (1998) reported that, half strength Gamborgs B5 medium supplemented with 5% sucrose and 1 mg/l of each of NAA and BA gave the best value for root culture growth of Datura candida x D. aurea. Meanwhile, full strength B5 medium supplemented with the same concentrations of NAA and BA gave the best results for hyoscyamine and scopolamine content. One of the methods frequently used to increase the productivity of plant cell culture is the use of so-called elicitors (Singh, 1996). Elicitors can be all types of compound that increase the production of phytoalexins (Muller, 1956 and Kuc, 1972). Phytoalexins are antibiotically active compounds and, by that, important factors in the Proc. Int. Conf. on MAP Eds. J. Bernáth et al. Acta Hort. 597, ISHS 2003

Identification of a P5 retrotransposon-like element in Sclerospora graminicola and contemplation of its role

Abstract: Sclerospora graminicola is an obligate parasite of its natural host pearl millet, Pennisetum glaucum and causes economic losses of the crop in semi-arid regions of Asia and Africa. The pathogen is capable of infecting a previously resistant host as it evolves rapidly to new virulent forms, a characteristic of retrotransposon activation. Retrotransposons are mobile repeat elements, and are known to mutate the organism's genes on activation by abiotic and biotic stress factors. We screened the λgt11 genomic library of the Path-6 isolate of S. graminicola with P5 retroelement, which belongs to the copia-like retrotransposon family. The library clones, designated as SgP5-1, SgP5-2, SgP5-3 and SgP5-4 were found to be distributed invariantly among genomes of five host-genotype-specific downy mildew pathotypes. At the RNA level, an amplified expression of P5-like sequences and an additional band of size 1.8 kb were found in compatible host–pathogen interaction but not in the incompatible system. This finding indicates that the fungus may be actively expressing the P5-like sequences in the host and the element is suppressed in a resistant host. Such an evidence for the role of retroelements in pearl millet-downy mildew interaction is being proposed for the first time.

Scientific revolutions, abiotic stress tolerance, and forestry

Abstract: SUMMARY Plant biotechnology - especially in vitro regeneration and cell biology, DNA manipulation and biochemical engineering - is already changing the agricultural scene in three major areas: control of plant growth, protecting plants against biotic stress, and production of specialty foods, biochemicals and pharmaceuticals. Plant biotechnology faces several major challenges in the coming decades: alleviating the hazards of abiotic stress (especially salinity, drought, and extreme temperatures), improving pest control, maintenance and improvement of the environment, improvement of food quality and design of 'specialty food' using biochemical engineering, and production of biomaterials. Two parallel research approaches will most likely exist simultaneously in the near future: the transgenic approach (expression of unique genes and specific promoters and transcription factors), and the non-transgenic approach (genomics-assisted gene discovery, marker-assisted selection, efficient mutations, and clonal agriculture). Drought and salinity are the most serious threats to agriculture and to the environment in many parts of the world. Key molecular factors that are being used for genetic engineering of stress-tolerant plants include: over-expression of specific transcription factors, characterization of dehydrin proteins, over-production of osmoprotectants, expression of water channel proteins and ion transporters, expression and characterization of molecular chaperones, including a novel boiling-stable homo-oligomeric SP1 protein. Although molecular breeding is routine in agriculture, forest-tree species have been left far behind. However, the increasing demand for wood and its products and the reduction of available harvestable forests has recently led to the introduction of several molecular and biotechnological tools into forest-tree research and improvement. Among these are in vitro propagation, the identification of molecular markers, and genetic engineering for specific traits. Achievements today in plant biotechnology have already surpassed all previous expectations. The full realization and impact of the new developments depend not only on continued successful and innovative research and development activities, but also on a favorable regulatory climate and public acceptance. Plant scientists now have a central role in society.