Nitrate- and nitric oxide-induced plant growth in pea seedlings is linked to antioxidative metabolism and the ABA/GA balance

This study looks at the effects of potassium nitrate (KNO3) and sodium nitroprusside (SNP), a nitric oxide (NO)-donor, on the development, antioxidant defences and on the abscisic acid (ABA) and gibberellin (GA) levels inpea seedlings. Results show that 10 mM KNO3and 50μM SNP stimulate seedling fresh weight (FW), althoughthis effect is not reverted by the action of 2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide(cPTIO), a NO-scavenger.The KNO3treatment increased peroxidase (POX) and ascorbate oxidase (AOX) activities. SNP, on the otherhand, reduced monodehydroascorbate reductase (MDHAR) activity and produced a significant increase in su-peroxide dismutase (SOD), POX and AOX activities. The“KNO3plus cPTIO”treatment increased ascorbateperoxidase (APX), MDHAR, glutathione reductase (GR) and SOD activities, but POX activity decreased in re-lation to the KNO3treatment. The“SNP plus cPTIO”treatment increased APX and MDHAR activities, whereas ahuge decrease in POX activity occurred. Both the KNO3and the SNP treatments increased reduced ascorbate(ASC) concentrations, which reached control values in the presence of cPTIO. All treatments increased thedehydroascorbate (DHA) level in pea seedlings, leading to a decrease in the redox state of ascorbate. In the“KNO3plus cPTIO”treatment, an increase in the redox state of ascorbate was observed. Glutathione contents,however, were higher in the presence of SNP than in the presence of KNO3. In addition, KNO3produced anaccumulation of oxidised glutathione (GSSG), especially in the presence of cPTIO, leading to a decrease in theredox state of glutathione. The effect of SNP on reduced glutathione (GSH) levels was reverted by cPTIO, sug-gesting that NO has a direct effect on GSH biosynthesis or turnover.Both the KNO3and SNP treatments produced an increase in GA4 and a decrease in ABA concentrations, andthis effect was reverted in the presence of the NO-scavenger. Globally, the results suggest a relationship betweenantioxidant metabolism and the ABA/GA balance during early seedling growth in pea. The results also suggest arole for KNO3and NO in the modulation of GA4 and ABA levels and antioxidant metabolism in pea seedlings.Furthermore, this effect correlated with an increase in the biomass of the pea seedlingsinfo:eu-repo/semantics/acceptedVersio

Metabolomics and biochemical approaches link salicylic acid biosynthesis to cyanogenesis in peach plants

Despite the long-established importance of salicylic acid (SA) in plant stress responses and other biological processes, its biosynthetic pathways have not been fully characterized. The proposed synthesis of SA originates from chorismate by two distinct pathways: the isochorismate and phenylalanine (Phe) ammonia-lyase (PAL) pathways. Cyanogenesis is the process related to the release of hydrogen cyanide from endogenous cyanogenic glycosides (CNglcs), and it has been linked to plant plasticity improvement. To date, however, no relationship has been suggested between the two pathways. In this work, by metabolomics and biochemical approaches (including the use of [C-13]-labeled compounds), we provide strong evidences showing that CNglcs turnover is involved, at least in part, in SA biosynthesis in peach plants under control and stress conditions. The main CNglcs in peach are prunasin and amygdalin, with mandelonitrile (MD), synthesized from phenylalanine, controlling their turnover. In peach plants MD is the intermediary molecule of the suggested new SA biosynthetic pathway and CNglcs turnover, regulating the biosynthesis of both amygdalin and SA. MD-treated peach plants displayed increased SA levels via benzoic acid (one of the SA precursors within the PAL pathway). MD also provided partial protection against Plum pox virus infection in peach seedlings. Thus, we propose a third pathway, an alternative to the PAL pathway, for SA synthesis in peach plantsThis work was supported by the Spanish Ministry of Economy and Competitiveness (Project AGL2014-52563-R). PDV and CP thank CSIC and UPCT, respectively, as well as the Spanish Ministry of Economy and Competitiveness for their ‘Ramon & Cajal’ research contract, co-financed by FEDER funds. We also acknowledge Prof. Manuel Acosta Echeverría for his very useful commentaries and discussion

Trichoderma harzianum T-78 supplementation of compost stimulates the antioxidant defence system in melon plants

[Background] Compost is emerging as an alternative plant growing medium in efforts to achieve more sustainable agriculture. The addition of specific microorganisms such as Trichoderma harzianum to plant growth substrates increases yields and reduces plant diseases, but the mechanisms of such biostimulants and the biocontrol effects are not yet fully understood. In this work we investigated how the addition of citrus and vineyard composts, either alone or in combination with T. harzianum T-78, affects the antioxidant defence system in melon plants under nursery conditions.[Results] Compost application and/or Trichoderma inoculation modulated the antioxidant defence system in melon plants. The combination of citrus compost and Trichoderma showed a biostimulant effect that correlated with an increase in ascorbate recycling enzymes (monodehydroascorbate reductase, dehydroascorbate reductase) and peroxidase. Moreover, the inoculation of both composts with Trichoderma increased the activity of antioxidant enzymes, especially those involved in ascorbate recycling.[Conclusion] Based on the long-established relationship between ascorbic acid and plant defence responses as well as plant growth and development, it can be suggested that ascorbate recycling activities play a major role in the protection provided by Trichoderma and its biostimulant effect and that these outcomes are linked to increases in antioxidant enzymes. We can conclude that the combination of citrus compost and T. harzianum T-78 constitutes a viable, environmentally friendly strategy for improving melon plant production. © 2014 Society of Chemical IndustryThis work was supported by the FPU Programme of the Spanish Ministry of Education and the CYCIT AGL2010-21073 project from the Spanish Ministry of Economy and Competitivity. The study was also carried out as part of the Excellence Group, reference 04537/GERM/06, funded by the Seneca Foundation (Murcia, Spain). P.D.V. acknowledges CSIC and the Spanish Ministry of Economy and Competitiveness for his “Ramon y Cajal” research contract, co-financed with FEDER funds.Peer reviewe

The salt-stress response of the transgenic plum line J8-1 and its interaction with the salicylic acid biosynthetic pathway from mandelonitrile

Salinity is considered as one of the most important abiotic challenges that affect crop productivity. Plant hormones, including salicylic acid (SA), are key factors in the defence signalling output triggered during plant responses against environmental stresses. We have previously reported in peach a new SA biosynthetic pathway from mandelonitrile (MD), the molecule at the hub of the cyanogenic glucoside turnover in Prunus sp. In this work, we have studied whether this new SA biosynthetic pathway is also present in plum and the possible role this pathway plays in plant plasticity under salinity, focusing on the transgenic plum line J8-1, which displays stress tolerance via an enhanced antioxidant capacity. The SA biosynthesis from MD in non-transgenic and J8-1 micropropagated plum shoots was studied by metabolomics. Then the response of J8-1 to salt stress in presence of MD or Phe (MD precursor) was assayed by measuring: chlorophyll content and fluorescence parameters, stress related hormones, levels of non-enzymatic antioxidants, the expression of two genes coding redox-related proteins, and the content of soluble nutrients. The results from in vitro assays suggest that the SA synthesis from the MD pathway demonstrated in peach is not clearly present in plum, at least under the tested conditions. Nevertheless, in J8-1 NaCl-stressed seedlings, an increase in SA was recorded as a result of the MD treatment, suggesting that MD could be involved in the SA biosynthesis under NaCl stress conditions in plum plants. We have also shown that the plum line J8-1 was tolerant to NaCl under greenhouse conditions, and this response was quite similar in MD-treated plants. Nevertheless, the MD treatment produced an increase in SA, jasmonic acid (JA) and reduced ascorbate (ASC) contents, as well as in the coefficient of non-photochemical quenching (qN) and the gene expression of Non-Expressor of Pathogenesis-Related 1 (NPR1) and thioredoxin H (TrxH) under salinity conditions. This response suggested a crosstalk between different signalling pathways (NPR1/Trx and SA/JA) leading to salinity tolerance in the transgenic plum line J8-1.This work was supported by the Spanish Ministry of Economy and Competitiveness (Projects AGL2014-52563-R and INIA-RTA2013-00026-C03-00). PDV and CP thank CSIC and UPCT, respectively, as well as the Spanish Ministry of Economy and Competitiveness for their ‘Ramon and Cajal’ research contract, co-financed by FEDER funds. This work was supported by the Spanish Ministry of Economy and Competitiveness (Projects AGL2014-52563-R and INIA-RTA2013-00026-C03-00).Peer reviewe

Plant Responses to Salt Stress: Adaptive Mechanisms

This article belongs to the Special Issue Further Metabolism in Plant System.This review deals with the adaptive mechanisms that plants can implement to cope with the challenge of salt stress. Plants tolerant to NaCl implement a series of adaptations to acclimate to salinity, including morphological, physiological and biochemical changes. These changes include increases in the root/canopy ratio and in the chlorophyll content in addition to changes in the leaf anatomy that ultimately lead to preventing leaf ion toxicity, thus maintaining the water status in order to limit water loss and protect the photosynthesis process. Furthermore, we deal with the effect of salt stress on photosynthesis and chlorophyll fluorescence and some of the mechanisms thought to protect the photosynthetic machinery, including the xanthophyll cycle, photorespiration pathway, and water-water cycle. Finally, we also provide an updated discussion on salt-induced oxidative stress at the subcellular level and its effect on the antioxidant machinery in both salt-tolerant and salt-sensitive plants. The aim is to extend our understanding of how salinity may affect the physiological characteristics of plants.PDV thanks CSIC and the Spanish Ministry of Economy and Competitiveness for their ‘Ramon & Cajal’ research contract, co-financed by FEDER funds. We thank Spanish Ministry of Economy and Competitiveness (Project AGL2014-52563-R) and Seneca Foundation of Murcia (Project 19903/GERM/15)

Salt-tolerance mechanisms induced in Stevia rebaudiana Bertoni: Effects on mineral nutrition, antioxidative metabolism and steviol glycoside content

In order to cope with challenges linked to climate change such as salinity, plants must develop a wide spectrum of physiological and molecular mechanisms to rapidly adapt. Stevia rebaudiana Bertoni plants are a case in point. According to our findings, salt stress has no significant effect on plant growth in these plants, which accumulate sodium (Naþ) in their roots, thus avoiding excessive Naþ accumulation in leaves. Furthermore, salt stress (NaCl stress) increases the potassium (Kþ), calcium (Ca2þ), chloride ion (Cl ) and proline concentrations in Stevia leaves, which could contribute to osmotic adjustment. We also found that long-term NaCl stress does not produce changes in chlorophyll concentrations in Stevia leaves, reflecting a mechanism to protect the photosynthesis process. Interestingly, an increase in chlorophyll b (Chlb) content occured in the oldest plants studied. In addition, we found that NaCl induced reactive oxygen species (ROS) accumulation in Stevia leaves and that this accumulation was more evident in the presence of 5 g/L NaCl, the highest concentration used in the study. Nevertheless, Stevia plants are able to induce (16 d) or maintain (25 d) antioxidant enzymes to cope with NaCl-induced oxidative stress. Low salt levels did not affect steviolbioside and rebaudioside A contents. Our results suggest that Stevia plants induce tolerance mechanisms in order to minimize the deleterious effects of salt stress. We can thus conclude that saline waters can be used to grow Stevia plants and for Steviol glycosides (SGs) production.Para hacer frente a los retos relacionados con el cambio climático, como la salinidad, las plantas deben desarrollar un amplio espectro de mecanismos fisiológicos y moleculares para adaptarse rápidamente. Las plantas de Stevia rebaudiana Bertoni son un buen ejemplo. Según nuestros hallazgos, el estrés salino no tiene efectos significativos sobre el crecimiento de estas plantas, que acumulan sodio (Naþ) en sus raíces, evitando así una acumulación excesiva de Naþ en las hojas. Además, el estrés salino (estrés por NaCl) aumenta las concentraciones de potasio (Kþ), calcio (Ca2þ), ión cloruro (Cl) y prolina en las hojas de Stevia, lo que podría contribuir al ajuste osmótico. También encontramos que el estrés por NaCl a largo plazo no produce cambios en las concentraciones de clorofila en las hojas de Stevia, lo que refleja un mecanismo para proteger el proceso de fotosíntesis. Curiosamente, se produjo un aumento en el contenido de clorofila b (Chlb) en las plantas más viejas estudiadas. Además, encontramos que el NaCl indujo la acumulación de especies reactivas de oxígeno (ROS) en las hojas de Stevia y que esta acumulación fue más evidente en presencia de 5 g/L de NaCl, la concentración más alta utilizada en el estudio. Sin embargo, las plantas de Stevia son capaces de inducir (16 d) o mantener (25 d) enzimas antioxidantes para hacer frente al estrés oxidativo inducido por NaCl. Los bajos niveles de sal no afectaron a los contenidos de esteviolbósido y rebaudiósido A. Nuestros resultados sugieren que las plantas de Stevia inducen mecanismos de tolerancia para minimizar los efectos nocivos del estrés salino. Por lo tanto, podemos concluir que las aguas salinas pueden utilizarse para cultivar plantas de Stevia y para la producción de glucósidos de esteviol (SG).Agricultura y VeterinariaCiencias AmbientalesCiencias de la Alimentació

Small RNA-Seq to Characterize Viruses Responsible of Lettuce Big Vein Disease in Spain

The emerging lettuce big-vein disease (LBVD) is causing losses in lettuce production ranging from 30 to 70% worldwide. Several studies have associated this disease with Mirafiori lettuce big-vein virus (MiLBVV) alone or in mixed infection with lettuce big-vein associated virus (LBVaV). We used Illumina small RNA sequencing (sRNA-seq) to identify viruses present in symptomatic lettuce plants from commercial fields in Southern Spain. Data analysis using the VirusDetect tool showed the consistent presence of MiLBVV and LBVaV in diseased plants. Populations of MiLBVV and LBVaV viral small RNAs (sRNAs) were characterized, showing features essentially similar to those of other viruses, with the peculiarity of an uneven asymmetric distribution of MiLBVV virus-derived small RNAs (vsRNAs) for the different polarities of genomic RNA4 vs. RNAs1 to 3. Sanger sequencing of coat protein genes was used to study MiLBVV and LBVaV phylogenetic relationships and population genetics. The Spanish MiLBVV population was composed of isolates from three well-differentiated lineages and reflected almost all of the diversity reported for the MiLBVV species, whereas the LBVaV population showed very little genetic differentiation at the regional scale but lineage differentiation at a global geographical scale. Universal primers were used to detect and quantify the accumulation of MiLBVV and LBVaV in field samples; both symptomatic and asymptomatic plants from affected fields carried equal viral loads, with LBVaV accumulating at higher levels than MiLBVV.CG-A was recipient of grant PTQ-15-07646 from the Torres-Quevedo program (Ministry of Economy, Industry and Competitiveness; Spain) and CT of fellowship DI-14-06825 from the Industrial Doctoral program (Ministry of Economy, Industry and Competitiveness, Spain).Peer reviewe

Producto sólido eficaz para el control biológico de la fusariosis vascular del melón, su procedimiento de obtención y método de aplicación del mismo

Fecha de solicitud: 03-07-2008.- Titular: Consejo Superior de Investigaciones Científicas (CSIC)Solid product effective for biocontrol of vascular fusariosis of melon, method for preparation thereof and method for use of same. The invention is part of the technical field of conventional and organic agriculture, is applicable both in fields and nurseries and provides a solid product effective for the biological control of vascular fusariosis of melon based on the use of a strain of T. harzianum, a fungus antagonistic to the pathogen (F. oxysporum sp. melonis), on an inert solid carrier and incorporates additional factors which improve the biocontrol capacity of the product. The invention also relates to the method for preparing the product and the method of use thereof.Producto sólido eficaz para el biocontrol del fusariosis vascular del melón, el método para la preparación de eso y el método para el uso de mismo. La invención es parte del campo industrial de la agricultura convencional y orgánica, es aplicable ambos en campos y cuartos de niños y proporciona un producto sólido eficaz para el control biológico del fusariosis vascular del melón basado en el uso de una cepa del T. harzianum, un hongo antagonisto al patógeno (F. SP del oxysporum. los melonis), en un vehículo del sólido inerte y incorporan los factores adicionales que mejoran la capacidad del biocontrol del producto. La invención también relaciona al método para preparar el producto y el método de uso de eso.Peer reviewe