Acta Physiologiae Plantarum

Gwóźdź, Edward

doi: 10.1007/s11738-997-0035-4pmid: N/A

Bartels, D.; Chandler, J.; Bockel, C.; Frank, W.; Kleines, M.; Rodrigo, M.; Phillips, J.; Mariaux, J.; Furini, A.; Salamini, F.

doi: 10.1007/s11738-997-0036-3pmid: N/A

The array of genes isolated and characterised from Craterostigma to date allow many insights to be made into the protection mechanisms underlying the desiccation tolerance phenomenon and drought-induced changes in gene expression. However, more work is necessary to define which gene products positively contribute to stress tolerance and which may be considered as secondary stress metabolites or as gene regulators. It is apparent that the gene regulatory mechanisms involved are complex, but future work with more refined biochemical and genetic approaches, together with the analysis of defined mutants will greatly help to dissect the important area of desiccation perception, perhaps faciliate manipulation of desiccation tolerance in a genetic engineering context, and undoubtedly bring much progress in the coming years.

Bray, Elizabeth; Cohen, Amybeth; Plant, Áine; Moses, Meena; Imai, Ryozo; Griffiths, Allen

doi: 10.1007/s11738-997-0037-2pmid: N/A

In response to water deficit, endogenous abscisic acid (ABA) accumulates in plants. This ABA serves as a signal for a multitude of processes, including regulation of gene expression. ABA accumulated in response to water deficit signals cellular as well as whole plant responses playing a role in the pattern of gene expression throughout the plant. Although the function of genes regulated by ABA during stress are currently poorly understood, a number of these genes may permit the plant to adapt to environmental stress.

Oliver, Melvin; Wood, Andrew; O’Mahony, Patrick

doi: 10.1007/s11738-997-0038-1pmid: N/A

Desiccation-tolerant plants can be grouped into two categories: the 1) desiccation-tolerant plants whose internal water content rapidly equilibrates to the water potential of the environment and 2) the modified desiccation-tolerant plants that all employ mechanisms to retard and control the rate of water loss. Desiccation tolerance can be achieved by mechanisms that incorporate one of two alternatives, viz. cellular protection or cellular recovery (repair). The majority of plants probably utilize aspects of both. Desiccation-tolerant species, in particular the moss Tortula ruralis, appear to utilize a tolerance strategy that combines a constitutive protection system and a rehydration-inducible recovery mechanism. The rehydration-induced recovery mechanism of Tortula ruralis relies heavily upon a change in gene expression that is mediated by posttranscriptional events rather than the slower reacting transcriptional controls. Findings indicate that it takes a certain amount of prior water loss to fully activate the protein-based portion of the recovery mechanisms upon rehydration. Utilizing cDNAs representing individual hydrins (proteins whose synthesis is hydration specific) and rehydrins (proteins whose synthesis is rehydration specific), it was determined that if drying rates were slow rehydrin transcripts selectively accumulate in the dried gametophytes. Studies revealed that this storage involves the formation of mRNPs (messenger ribonucleoprotein particles). The identity and possible functions of the rehydrins of Tortula ruralis are also under investigation, in particular Tr155, a small rehydrin (24kD) appears to be involved in antioxidant production during rehydration.

Flowers, Timothy; Garcia, Aurora; Koyama, Mikiko; Yeo, Anthony

doi: 10.1007/s11738-997-0039-0pmid: N/A

Salinity in soil affects about 7 % of the land’s surface and about 5 % of cultivated land. Most importantly, about 20 % of irrigated land has suffered from secondary salinisation and 50 % of irrigation schemes are affected by salts. In many hotter, drier countries of the world salinity is a concern in their agriculture and could become a key issue. Consequently, the development of salt resistant crops is seen as an important area of research. Although there has been considerable research into the effects of salts on crop plants, there has not, unfortunately, been a commensurate release of salt tolerant cultivars of crop plants. The reason is likely to be the complex nature of the effect of salts on plants. Given the rapid increase in molecular biological techniques, a key question is whether such techniques can aid the development of salt resistance in plants.

Winicov, Ilga; Bastola, Dhundy

doi: 10.1007/s11738-997-0040-7pmid: N/A

Recent approaches to study of salinity tolerance in crop plants have ranged from genetic mapping to molecular characterization of gene products induced by salt/drought stress. Transgenic plant design has allowed to test the effects of overexpression of specific prokaryotic or plant genes that are known to be up-regulated by salt/drought stress. This review summarizes current progress in the field in the context of adaptive metabolic and physiological responses to salt stress and their potential role in long term tolerance. Specifically considered are gene activation by salt, in view of proposed avenues for improved salt tolerance and the need to ascertain the additional influences of developmental regulation of such genes. Discussion includes the alternate genetic strategy we have pursued for improving salinity tolerance in alfalfa (Medicago sativa L.) and rice (Oryza sativa L.). This strategy combines single-step selection of salt-tolerant cells in culture, followed by regeneration of salt-tolerant plants and identification of genes important in conferring salt tolerance. We have postulated that activation or improved expression of a subset of genes encoding functions that are particularly vulnerable under conditions of salt-stress could counteract the molecular effects of such stress and could provide incremental improvements in tolerance. We have proceeded to identify the acquired specific changes in gene regulation for our salt-tolerant mutant cells and plants. One particularly interesting and novel gene isolate from the salt-tolerant cells is Alfin1, which encodes a putative zinc-finger regulatory protein, expressed predominantly in roots. We have demonstrated that this protein binds DNA in a sequence specific manner and may be potentially important in gene regulation in roots in response to salt and an important marker for salt tolerance in crop plants.

Fordham-Skelton, Anthony; Wilson, Jonathan; Groom, Quentin; Robinson, Nigel

doi: 10.1007/s11738-997-0041-6pmid: N/A

It has been proposed that plant metallothionein (MT) sequesters excess copper, and possibly zinc, thereby preventing adverse metal-protein interactions. These metals can accumulate either gratuitously in response to other nutritional deficiencies or in plants grown in either copper- or zinc-enriched medium. Data are presented which confirm that in pea roots grown in low available iron there is increased (i) copper accumulation, (ii) MT transcript abundance, (iii) ferric-chelate reductase activity and (iv) cupric-chelate reductase activity. It is also shown that in roots grown in iron supplemented medium MT transcripts accumulate in response to elevated exogenous zinc. However, contrary to expectations, depletion of exogenous copper below normal micronutrient levels also confers an increase in the abundance of MT transcripts.

Gwóźdź, Edward; Przymusiński, Roman; Rucińska, Renata; Deckert, Joanna

doi: 10.1007/s11738-997-0042-5pmid: N/A

The effect of lead, cadmium and cooper on protein pattern, free radicals and antioxidant enzymes in root of Lupinus luteus L. were investigated. Heavy metals inhibited growth of lupin roots, which was accompanied by increased synthesis and accumulation of a 16 kDa polypeptide (Przymusiński et al. 1991 Biochem. Physiol. Pflanzen., 187:51–57). This component has been earlier identified as immunologically related to Cu,Zn-superoxide dismutase (Przymusiński et al. 1995 Env.Exp.Bot., 35:485–495). However, more detailed study revealed that this stress-stimulated protein is composed of four to six polypeptides of different electrophoretic mobility. The most abundant polypeptides of the 16kDa region were found to be closely homologous to pathogen related proteins. The number and intensity of these polypeptides was highly variable in roots of individual seedlings, which suggests that they might represent separate allelic forms.

Grimmig, Bernhard; Schubert, Roland; Fischer, Regina; Hain, Rüdiger; Schreier, Peter; Betz, Christian; Langebartels, Christian; Ernst, Dieter; Sandermann, Heinrich

doi: 10.1007/s11738-997-0043-4pmid: N/A

Stilbene synthases (STSs) are enzymes that play a critical role in the biosynthesis of stilbene, phytoalexins in a small number of unrelated plant species, and are induced by various biotic and abiotic stressors like pathogen attack, UV-irradiation or ozone exposure. To investigate the molecular basis for ozone-induced plant stress responses, we have examined the promoter of the grapevine resveratrol synthase (Vst1). In this report we summarize the influence of ozone on gene regulation. In transgenic tobacco a chimeric gene construct, containing the Vst1 promoter combined with the β-glucuronidase (GUS) reporter gene, is rapidly induced by ozone (0.1 µl·l−1, 12 h). The same construct is also strongly induced by ethylene (20 µl·l−1, 12 h). Promoter deletion analysis of the 5′ flanking sequence identified a positive regulatory element between −430 bp and −280 bp. This region contains ethylene-responsive enhancer elements, as well as an elicitor-responsive sequence in inverse orientation.

Bowler, Chris; Frohnmeyer, Hanns; Schäfer, Eberhard; Neuhaus, Gunther; Chua, Nam-Hai

doi: 10.1007/s11738-997-0044-3pmid: N/A

The phytochromes are the best studied plant photoreceptors, controlling a wide variety of responses at both whole plant and single cell levels. Three signal transduction pathways, dependent on cGMP and/or calcium, have been found to be utilized by phytochrome to control the expression of genes required for chloroplast development (e.g., CAB and FNR) and anthocyanin biosynthesis (e.g., CHS). In particular, cGMP is a second messenger positively regulating CHS gene expression whilst calcium and calmodulin act as negative regulators. In addition to phytochrome regulation of CHS we have begun to examine the signal transduction pathways utilized by UV photoreceptors. In contrast to phytochrome-mediated responses, results indicate a role for calcium and calmodulin as positive regulators of CHS gene expression in UV light.