Plant Cell Wall Plasticity under Stress Situations

[EN] This Special Issue, entitled “Plant Cell Wall Plasticity under Stress Situations”, is a compilation of five articles, whose authors deepen our understanding of the roles of different cell wall components under biotic and abiotic stress. The plant cell wall is mainly formed of complex polysaccharides, with multiple interactions between the components that form a network which must be extensible, so as to enable cell expansion, rigid, so as to resist compression and tension forces, and modifiable in response to environmental changes. Cellulose, the most abundant and resistant polysaccharide on earth, is the main component of the cell wall. The cellulose scaffold is involved in a matrix formed of polysaccharides, such as pectins and hemicelluloses, whose types and proportions vary depending on the species, tissue, and cell type. The deposition of lignin—the second most abundant polymer on earth—in secondary cell walls increases the resistance, leading to growth cessation. All these polymers are crosslinked into the wall in a process that can occur spontaneously and/or by the actions of different modifying enzymes. The control of the synthesis of these cell wall components and/or the interactions between them gives this structure a high plasticity, which is a key factor in the modulation of growth and defense responses under different types of stress.S

La obra de teatro como metodología docente para la adquisición de competencias: ¿un Aprendizaje Basado en Problemas más?

Mención honorífica 2015[ES] El Aprendizaje Basado en Problemas (ABP) o Problem Based Learning (PBL) es una metodología docente muy utilizada que se puede adaptar y emplear en distintas áreas de conocimiento. Además es una actividad muy versátil, puesto que tanto la variedad de problemas que es posible plantear, como el grado de dificultad pueden ser muy amplios. Aprovechando esa versatilidad, nos propusimos como novedad aplicar toda una batería de recursos y herramientas que habíamos elaborado para el desarrollo del ABP en una asignatura del Grado en Biotecnología a la realización y representación de una obra de teatro

Using Plant-Based Preparations to Protect Common Bean against Halo Blight Disease: The Potential of Nettle to Trigger the Immune System

[EN] Halo blight disease of beans (Phaseolus vulgaris L.), caused by the bacterium Pseudomonas syringae pv. phaseolicola (Pph), is responsible for severe losses in crop production worldwide. As the current agronomic techniques used are not effective, it is necessary to search for new ones which may prevent disease in common bean. In this study, we challenged four plant-based preparations (PBPs), with no other agronomic uses, as they come from industrial waste (grapevine pomace (RG) and hop residue (RH)) or wild plants (Urtica dioica (U) and Equisetum sp. (E)), to be used as immune defense elicitors against Pph in common bean. After studying their inhibitory effect against Pph growth by bioassays, the two most effective PBPs (RG and U) were applied in common bean plants. By measuring the total H2O2, lipid peroxidation, and antioxidant enzymatic activities, as well as the expression of six defense-related genes—PR1, WRKY33, MAPKK, RIN4, and PAL1—, it was observed that U-PBP application involved a signaling redox process and the overexpression of all genes, mostly PR1. First infection trials in vitro suggested that the application of U-PBP involved protection against Pph. The elicitation of bean defense with U-PBP involved a decrease in some yield parameters, but without affecting the final production. All these findings suggest a future use of U-PBP to diminish halo blight disease.SIThis research was funded by the Spanish Ministry of Economy, Industry and Competitiveness, grant number RTC-2016-5816-2

Potencial de las infusiones de ortiga (Urtica dioica L.) para proteger a la alubia común (Phaseolus vulgaris L.) de la enfermedad de la grasa.

[ES] El empleo de preparados basados en plantas que sustituyan a los fitosanitarios químicos es un reto para la agricultura sostenible. Las suspensiones acuosas (Us) de ortiga (Urtica dioica L.) son un candidato pues el tratamiento con Us de plantas de alubia común (Phaseolus vulgaris L.) redujo los síntomas de la enfermedad de la grasa causada por Pseudomonas syringae pv. phaseolicola (Pph) (De la Rubia et al., 2022). Sin embargo, el uso de Us como producto agrícola final entraña ciertos problemas. El objetivo del presente trabajo fue comprobar si las infusiones de ortiga (Uin) tienen el mismo efecto y, en caso afirmativo, conocer a qué tipo de actividad podría deberse: antimicrobiana, promotora de las defensas naturales de la planta y/o antioxidante. Para ello, se hicieron ensayos de crecimiento de Pph en presencia de Uin, de liberación de H2O2 en respuesta a flagelina en discos foliares preincubados con Uin y de estimación de la capacidad antioxidante de Uin. Los resultados apuntan a que las propiedades protectoras de la infusión se deben al contenido en compuestos bioactivos antioxidantes. Además, se probó que el pretratamiento de las plantas con Uin disminuía el daño oxidativo foliar provocado tras 6 horas de infección con Pph, lo que refuerza esta idea

Cellulose Biosynthesis Inhibitors: Comparative Effect on Bean Cell Cultures

[EN] The variety of bioassays developed to evaluate different inhibition responses for cellulose biosynthesis inhibitors makes it difficult to compare the results obtained. This work aims (i) to test a single inhibitory assay for comparing active concentrations of a set of putative cellulose biosynthesis inhibitors and (ii) to characterize their effect on cell wall polysaccharides biosynthesis following a short-term exposure. For the first aim, dose-response curves for inhibition of dry-weight increase following a 30 days exposure of bean callus-cultured cells to these inhibitors were obtained. The compound concentration capable of inhibiting dry weight increase by 50% compared to control (I50) ranged from subnanomolar (CGA 325′615) to nanomolar (AE F150944, flupoxam, triazofenamide and oxaziclomefone) and micromolar (dichlobenil, quinclorac and compound 1) concentrations. In order to gain a better understanding of the effect of the putative inhibitors on cell wall polysaccharides biosynthesis, the [14C]glucose incorporation into cell wall fractions was determined after a 20 h exposure of cell suspensions to each inhibitor at their I50 value. All the inhibitors tested decreased glucose incorporation into cellulose with the exception of quinclorac, which increased it. In some herbicide treatments, reduction in the incorporation into cellulose was accompanied by an increase in the incorporation into other fractions. In order to appreciate the effect of the inhibitors on cell wall partitioning, a cluster and Principal Component Analysis (PCA) based on the relative contribution of [14C]glucose incorporation into the different cell wall fractions were performed, and three groups of compounds were identified. The first group included quinclorac, which increased glucose incorporation into cellulose; the second group consisted of compound 1, CGA 325′615, oxaziclomefone and AE F150944, which decreased the relative glucose incorporation into cellulose but increased it into tightly-bound cellulose fractions; and the third group, comprising flupoxam, triazofenamide and dichlobenil, decreased the relative glucose incorporation into cellulose and increased it into a pectin rich fraction.SISpanish Ministry of Science and Innovation programs ( AGL2011-30545-C02-02)This work was partly supported by grants from Junta de Castilla y León (LE 48A07

Immune Priming Triggers Cell Wall Remodeling and Increased Resistance to Halo Blight Disease in Common Bean

[EN] The cell wall (CW) is a dynamic structure extensively remodeled during plant growth and under stress conditions, however little is known about its roles during the immune system priming, especially in crops. In order to shed light on such a process, we used the Phaseolus vulgaris- Pseudomonas syringae (Pph) pathosystem and the immune priming capacity of 2,6-dichloroisonicotinic acid (INA). In the first instance we confirmed that INA-pretreated plants were more resistant to Pph, which was in line with the enhanced production of H2O2 of the primed plants after elicitation with the peptide flg22. Thereafter, CWs from plants subjected to the different treatments (non- or Pph-inoculated on non- or INA-pretreated plants) were isolated to study their composition and properties. As a result, the Pph inoculation modified the bean CW to some extent, mostly the pectic component, but the CW was as vulnerable to enzymatic hydrolysis as in the case of non-inoculated plants. By contrast, the INA priming triggered a pronounced CW remodeling, both on the cellulosic and non-cellulosic polysaccharides, and CW proteins, which resulted in a CW that was more resistant to enzymatic hydrolysis. In conclusion, the increased bean resistance against Pph produced by INA priming can be explained, at least partially, by a drastic CW remodeling.SIThis research was funded by the Spanish Ministry of Economy, Industry and Competitiveness, grant number RTC-2016-5816-2

The use of FTIR spectroscopy to monitor modifications in plant cell wall architecture caused by cellulose biosynthesis inhibitors

[EN] Fourier Transform InfraRed (FTIR) spectroscopy is a powerful and rapid technique for analyzing cell wall components and putative cross-links, which is able to non-destructively recognize polymers and functional groups and provide abundant information about their in muro organization. FTIR spectroscopy has been reported to be a useful tool for monitoring cell wall changes occurring in muro as a result of various factors, such as growth and development processes, mutations or biotic and abiotic stresses. This mini-review examines the use of FTIR spectroscopy in conjunction with multivariate analyses to monitor cell wall changes related to (1) the exposure of diverse plant materials to cellulose biosynthesis inhibitors (CBIs) and (2) the habituation/dehabituation of plant cell cultures to this kind of herbicides. The spectra analyses show differences not only regarding the inhibitor, but also regarding how long cells have been growing in its presence.SIThis work was supported by grants from Junta de Castilla y León (LE 17/04 and LE 48A07), University of León (ULE-2006-2

Habituation and dehabituation to dichlobenil. Simply the equivalent of Penélope’s weaving and unweaving process?

[EN] The habituation of cell cultures to cellulose biosynthesis inhibitors constitutes a valuable method for learning more about the plasticity of plant cell wall composition and structure. The subculture of habituated cells in the absence of an inhibitor (dehabituation) offers complementary information: some habituation-associated modifications revert, whereas others remain, even after long-term (3-5 years) dehabituation processes. However, is dehabituation simply the opposite to the process of habituation, in the same way that the cloth woven by Penélope during the day was unwoven during the night? Principal Component Analysis applied to Fourier Transformed Infrared (FTIR) spectra of cell walls from dichlobenil-habituated and dehabituated bean cell lines has shown that dehabituation follows a different pathway to that of habituation. Principal component loadings show that dehabituated cells have more pectins, but that these display a lower degree of methyl-esterification, than those of habituated ones. Further analysis of cell walls focusing on the first steps of habituation would serve to identify which specific modifications in pectins are responsible to the fine modulation of cell wall architecture observed during the habituation/dehabituation process.SIThis work was supported by grants from the Junta de Castilla y León (LE 048A07

Quinclorac-habituation of bean (Phaseolus vulgaris) cultured cells is related to an increase in their antioxidant capacity

7 p.The habituation of bean cells to quinclorac did not rely on cell wall modifications, contrary to what it was previously observed for the well-known cellulose biosynthesis inhibitors dichlobenil or isoxaben. The aim of the present study was to investigate whether or not the bean cells habituation to quinclorac is related to an enhancement of antioxidant activities involved in the scavenging capacity of reactive oxygen species. Treating non-habituated bean calluses with 10 μM quinclorac reduced the relative growth rate and induced a two-fold increase in lipid peroxidation. However, the exposition of quinclorac-habituated cells to a concentration of quinclorac up to 30 μM neither affected their growth rate nor increased their lipid peroxidation levels. Quinclorac-habituated calluses had significantly higher constitutive levels of three antioxidant activities (class-III peroxidase, glutathione reductase, and superoxide dismutase) than those observed in non-habituated calluses, and the treatment of habituated calluses with 30 μM quinclorac significantly increased the level of class III-peroxidase and superoxide dismutase. The results reported here indicate that the process of habituation to quinclorac in bean callus-cultured cells is related, at least partially, to the development of a stable antioxidant capacity that enables them to cope with the oxidative stress caused by quinclorac. Class-III peroxidase and superoxide dismutase activities could play a major role in the quinclorac-habituation. Changes in the antioxidant status of bean cells were stable, since the increase in the antioxidant activities were maintained in quinclorac-dehabituated cellsS

Early habituation of maize (Zea mays) suspension-cultured cells to 2,6- diclorobenzonitrile is associated with the enhancement of antioxidant status

30 p.The cellulose biosynthesis inhibitor 2,6-diclorobenzonitrile (DCB) has been widely used to gain insights into cell wall composition and architecture. Studies of changes occurring during incipient habituation to DCB can provide information on early cell mechanisms leading to cope with DCB-induced stress. In this context, maize cultured cells with a reduced amount of cellulose were obtained by stepwise habituation to low DCB concentrations. The results reported here attempt to elucidate the putative role of an antioxidant strategy during incipient habituation. The short-term exposure to DCB of non-habituated maize cultured cells induced a substantial increase in oxidative damage. Concomitantly, short-term treated cells presented an increase in class III peroxidase and glutathione S-transferase activities and total glutathione content. Maize cells habituated to 0.3 – 1 μM DCB (incipient habituation) were characterised by a reduction in the relative cell growth rate, an enhancement of ascorbate peroxidase and class III peroxidase activities, and a net increment in total glutathione content. Moreover, these cell lines showed increased levels of glutathione S-transferase activity. Changes in antioxidant/detoxifying status enabled 0.3 and 0.5 μM DCB-habituated cells to control lipid peroxidation levels, but this was not the case of maize cells habituated to 1 μM DCB, which despite showing an increased antioxidant capacity were not capable of reducing the oxidative damage to control levels. The results reported here confirm that exposure and incipient habituation of maize cells to DCB are associated with an enhancement in antioxidant/detoxifying activities which could play a role in incipient DCB habituation of maize cultured cellsS