Polyamines under Abiotic Stress: Metabolic Crossroads and Hormonal Crosstalks in Plants

Polyamines are essential compounds for cell survival and have key roles in plant stress protection. Current evidence points to the occurrence of intricate cross-talks between polyamines, stress hormones and other metabolic pathways required for their function. In this review we integrate the polyamine metabolic pathway in the context of its immediate metabolic network which is required to understand the multiple ways by which polyamines can maintain their homeostasis and participate in plant stress responses

Involvement of polyamine metabolism in the response of Medicago truncatula genotypes to salt stress

Salinity constitutes one of the most important causes leading to severe reduction in plant yield. Several reports correlate the accumulation of polyamines in plants with tolerance to abiotic stress cues. The present study examined three Medicago truncatula genotypes with differing sensitivities to salinity (TN1.11, tolerant; Jemalong A17, moderately sensitive; TN6.18, sensitive), with the aim of examining the genotype-specific involvement of the polyamine metabolic pathway in plant response to salinity. The study was carried out with leaves harvested 48 h after watering plants with 200 mM NaCl. A comprehensive profile of free polyamines was determined using high performance liquid chromatography. All genotypes showed spermidine and spermine as the most abundant polyamines under control conditions. In salinity conditions, spermine levels increased at the expense of putrescine and spermidine, indicating a drift of polyamine metabolism towards the synthesis of increasing polycationic forms as a stress response. The increasing balance between high and low polycationic forms was clearly diminished in the salt-sensitive genotype TN6.18, showing a clear correlation with its sensitive phenotype. The polyamine metabolic profile was then supported by molecular evidence through the examination of polyamine metabolism transcript levels by RT-qPCR. General suppression of genes that are involved upstream in the PA biosynthetic pathway was determined. Contrarily, an induction in the expression of genes involved in the biosynthesis of spermine and spermidine was observed, in agreement with the metabolic analysis. A significant induction in diamino oxidase expression, involved in the catabolism of putrescine, was specifically found in the sensitive genotype ΤΝ6.18, indicating a distinct metabolic response to stress. Present findings highlight the involvement of polyamines in the defense response of Medicago genotypes showing sensitivity to salt stress

Role for Arabidopsis PLC7 in Stomatal Movement, Seed Mucilage Attachment, and Leaf Serration

Phospholipase C (PLC) has been suggested to play important roles in plant stress and development. To increase our understanding of PLC signaling in plants, we have started to analyze knock-out (KO), knock-down (KD) and overexpression mutants of Arabidopsis thaliana, which contains nine PLCs. Earlier, we characterized PLC2, PLC3 and PLC5. Here, the role of PLC7 is functionally addressed. Promoter-GUS analyses revealed that PLC7 is specifically expressed in the phloem of roots, leaves and flowers, and is also present in trichomes and hydathodes. Two T-DNA insertion mutants were obtained, i.e., plc7-3 being a KO- and plc7-4 a KD line. In contrast to earlier characterized phloem-expressed PLC mutants, i.e., plc3 and plc5, no defects in primary- or lateral root development were found for plc7 mutants. Like plc3 mutants, they were less sensitive to ABA during stomatal closure. Double-knockout plc3 plc7 lines were lethal, but plc5 plc7 (plc5/7) double mutants were viable, and revealed several new phenotypes, not observed earlier in the single mutants. These include a defect in seed mucilage, enhanced leaf serration, and an increased tolerance to drought. Overexpression of PLC7 enhanced drought tolerance too, similar to what was earlier found for PLC3-and PLC5 overexpression. In vivo32Pi-labeling of seedlings and treatment with sorbitol to mimic drought stress, revealed stronger PIP2 responses in both drought-tolerant plc5/7 and PLC7-OE mutants. Together, these results show novel functions for PLC in plant stress and development. Potential molecular mechanisms are discussed

Role for arabidopsis PLC7 in stomatal movement, seed mucilage attachment, and leaf serration

Phospholipase C (PLC) has been suggested to play important roles in plant stress and development. To increase our understanding of PLC signaling in plants, we have started to analyze knock-out (KO), knock-down (KD) and overexpression mutants of Arabidopsis thaliana, which contains nine PLCs. Earlier, we characterized PLC2, PLC3 and PLC5. Here, the role of PLC7 is functionally addressed. Promoter-GUS analyses revealed that PLC7 is specifically expressed in the phloem of roots, leaves and flowers, and is also present in trichomes and hydathodes. Two T-DNA insertion mutants were obtained, i.e., plc7-3 being a KO- and plc7-4 a KD line. In contrast to earlier characterized phloem-expressed PLC mutants, i.e., plc3 and plc5, no defects in primary- or lateral root development were found for plc7 mutants. Like plc3 mutants, they were less sensitive to ABA during stomatal closure. Double-knockout plc3 plc7 lines were lethal, but plc5 plc7 (plc5/7) double mutants were viable, and revealed several new phenotypes, not observed earlier in the single mutants. These include a defect in seed mucilage, enhanced leaf serration, and an increased tolerance to drought. Overexpression of PLC7 enhanced drought tolerance too, similar to what was earlier found for PLC3-and PLC5 overexpression. In vivo 32Pi-labeling of seedlings and treatment with sorbitol to mimic drought stress, revealed stronger PIP2 responses in both drought-tolerant plc5/7 and PLC7-OE mutants. Together, these results show novel functions for PLC in plant stress and development. Potential molecular mechanisms are discussed.Fil: van Wijk, Ringo. University of Amsterdam; Países BajosFil: Zhang, Qianqian. University of Amsterdam; Países BajosFil: Zarza, Xavier. University of Amsterdam; Países BajosFil: Lamers, Mart. University of Amsterdam; Países BajosFil: Reyes Marquez, Francisca. Wageningen University and Research, Wageningen; Países BajosFil: Guardia, Aisha Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Biológicas. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Biológicas; ArgentinaFil: Scuffi, Denise. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Biológicas. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Biológicas; ArgentinaFil: Garcia-Mata, Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Biológicas. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Biológicas; ArgentinaFil: Ligterink, Wilco. Wageningen University and Research, Wageningen; Países BajosFil: Haring, Michel A.. University of Amsterdam; Países BajosFil: Laxalt, Ana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Biológicas. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Biológicas; ArgentinaFil: Munnik, Teun. University of Amsterdam; Países Bajo

Polyamine Oxidase 5 loss-of-function mutations in Arabidopsis thaliana trigger metabolic and transcriptional reprogramming and promote salt stress tolerance.

The family of polyamine oxidases (PAO) in Arabidopsis (AtPAO1-5) mediates polyamine (PA) back-conversion, which reverses the PA biosynthetic pathway from spermine, and its structural isomer thermospermine (tSpm), into spermidine and then putrescine. Here, we have studied the involvement of PA back-conversion in Arabidopsis salinity tolerance. AtPAO5 is the Arabidopsis PAO gene member most transcriptionally induced by salt stress. Two independent loss-of-function mutants (atpao5-2 and atpao5-3) were found to exhibit constitutively higher tSpm levels, with associated increased salt tolerance. Using global transcriptional and metabolomic analyses, the underlying mechanisms were studied. Stimulation of abscisic acid and jasmonates (JA) biosynthesis, and accumulation of important compatible solutes, such as sugars, polyols and proline, as well as TCA cycle intermediates were observed in atpao5 mutants under salt stress. Expression analyses indicate that tSpm modulates the transcript levels of several target genes, including many involved in the biosynthesis and signaling of JA, some of which are already known to promote salinity tolerance. Transcriptional modulation by tSpm is isomer-dependent, thus demonstrating the specificity of this response. Overall, we conclude that tSpm triggers metabolic and transcriptional reprogramming that promotes salt stress tolerance in Arabidopsis

La Responsabilidad Social Corporativa en tiempos de crisis

[spa] Hoy en día la población mundial está viviendo un momento de crisis, desde hace ya unos 6 años y del que está resultando complicada de salir, es por ello que en el presente Trabajo Fin de Grado se aborda en que manera ha podido la crisis afectar a las empresas en materia de Responsabilidad Social Corporativa, más concretamente en la empresa española Sol Meliá. Por tanto se lleva a cabo una revisión teórica en dicha materia para posteriormente analizar las acciones de Sol Meliá llevadas a cabo durante este período de crisis.[eng] Nowadays the people are living in a crisis moment from around 6 years ago, and it's proving difficult to get out of it, so in the next final project work we can see how the crisis affect to the companies about corporate social responsibility, punctually in the company Sol Meliá. Therefore we made a theorical review about it and then we analyze the actions that Sol Meliá did it during this period of crisis

Polyamines under abiotic stress: Metabolic crossroads and hormonal crosstalks in plants

This article belongs to the Special Issue Feature Papers.Polyamines are essential compounds for cell survival and have key roles in plant stress protection. Current evidence points to the occurrence of intricate cross-talks between polyamines, stress hormones and other metabolic pathways required for their function. In this review we integrate the polyamine metabolic pathway in the context of its immediate metabolic network which is required to understand the multiple ways by which polyamines can maintain their homeostasis and participate in plant stress responses.R.A. acknowledges support from the Ramón y Cajal Programme of the Ministry of Economy and Competitiveness, Spain. Research in our laboratory is financed by Spanish Ministry of Science and Education (BIO2008-05493-C02-01 and BIO2011-2963) and by the Generalitat de Catalunya (2009SGR1060).Peer reviewe

Integration of polyamins in the cold acclimation response

8 páginas, 1 figura, 3 tablas -- PAGS nros. 31-38Temperature is one of the most important environmental factors limiting the geographical distribution of plants and accounts for significant reductions in the yield of agriculturally important crops. Low temperature damages many plant species, especially those adapted to tropical climates. In contrast, some species from temperate regions are able to develop freezing tolerance in response to low-non-freezing temperature, an adaptive process named cold acclimation. Numerous molecular, biochemical and physiological changes occur during cold acclimation, most of them being associated with significant changes in gene expression and metabolite profiles. During recent years, transcriptomic and metabolomic approaches have allowed the identification of cold-responsive genes and main metabolites which accumulate in plants exposed to cold. The obtained data support the previously held idea that polyamines (PAs) are involved in plant responses to cold, although their specific role is still not well understood. In this review, we synthesize published data regarding PA-responses to cold stress and integrate them with global transcriptional and metabolic changes. The potential of PA genetic engineering for the development of plants resistant to cold and freezing temperatures, and their plausible mechanisms of action are also discussedOur research was supported by grants from the Ministerio de Ciencia e Innovación, Spain (BIO2008-05493-C02-01, CSD2007-00036) and the Comissionat per Universitats i Recerca (Generalitat de Catalunya, SGR2009-1060). Work in JS laboratory is supported by grants GEN2006-27787-E/VEG, BIO2007-65284, CSD2007-00057 and EUI2009-04074 from the Ministerio de Ciencia e Innovación, Spain, and grant P2006/GEN-0191 from the Regional Government of Madrid. AFT, JS, RA and PC also acknowledge grants-in-aid from COST-Action FA0605Peer reviewe

Putrescine Is Involved in Arabidopsis Freezing Tolerance and Cold Acclimation by Regulating Abscisic Acid Levels in Response to Low Temperature1

The levels of endogenous polyamines have been shown to increase in plant cells challenged with low temperature; however, the functions of polyamines in the regulation of cold stress responses are unknown. Here, we show that the accumulation of putrescine under cold stress is essential for proper cold acclimation and survival at freezing temperatures because Arabidopsis (Arabidopsis thaliana) mutants defective in putrescine biosynthesis (adc1, adc2) display reduced freezing tolerance compared to wild-type plants. Genes ADC1 and ADC2 show different transcriptional profiles upon cold treatment; however, they show similar and redundant contributions to cold responses in terms of putrescine accumulation kinetics and freezing sensitivity. Our data also demonstrate that detrimental consequences of putrescine depletion during cold stress are due, at least in part, to alterations in the levels of abscisic acid (ABA). Reduced expression of NCED3, a key gene involved in ABA biosynthesis, and down-regulation of ABA-regulated genes are detected in both adc1 and adc2 mutant plants under cold stress. Complementation analysis of adc mutants with ABA and reciprocal complementation tests of the aba2-3 mutant with putrescine support the conclusion that putrescine controls the levels of ABA in response to low temperature by modulating ABA biosynthesis and gene expression

Putrescine accumulation confers drought tolerance in transgenic Arabidopsis plants over-expressing the homologous Arginine decarboxylase 2 gene

In Arabidopsis, a model genus missing a functional ornithine decarboxylase pathway, most of the key genes involved in polyamine biosynthesis are duplicated. This gene redundancy has been related to the involvement of certain gene isoforms in the response to specific environmental stimuli. We have previously shown that drought stress induces Arginine decarboxlase 2 expression, while transcript levels for Arginine decarboxlase 1 remain constant. Accumulation of putrescine and increased arginine decarboxlase activity (EC 4.1.1.19) levels in response to different abiotic stresses have been reported in many different plant systems, but the biological meaning of this increase remains unclear. To get a new insight into these questions, we have studied the response to drought of transgenic Arabidopsis thaliana lines constitutively expressing the homologous Arginine decarboxlase 2 gene. These lines contain high levels of putrescine with no changes in spermidine and spermine content even under drought stress. Drought tolerance experiments indicate that the different degree of resistance to dehydration correlates with Put content. Although no significant differences were observed in the number of stomata between wild-type and transgenic plants, a reduction in transpiration rate and stomata conductance was observed in the ADC2 over-expressor lines. These results indicate that one of the mechanisms involved in the drought tolerance of transgenic plants over-producing Put is related to a reduction of water loss by transpiration.This work was supported by grants from the Spanish Government (BIO2008-05493-C02-01 and CSD2007-00036 “Centre for Research in Agrigenomics”) and the Comissionat per Universitats i Recerca (Generalitat de Catalunya, SGR2009-1060).Peer reviewe