Arbuscular Mycorrhizal Symbiosis Improves Ex Vitro Acclimatization of Sugarcane Plantlets (Saccharum spp.) under Drought Stress Conditions.

The symbiotic associations between arbuscular mycorrhizal fungi (AMF) and plants can induce drought stress tolerance. In this study, we evaluated the effect of Glomus intraradices, a mycorrhizal fungus, on the ex vitro development and survival of sugarcane plantlets subjected to drought stress during the acclimatization stage of micropropagation. In vitro obtained sugarcane plantlets (Saccharum spp. cv Mex 69-290) were inoculated with different doses of G. intraradices (0, 100, and 200 spores per plantlet) during greenhouse acclimatization. Sixty days after inoculation, plantlets were temporarily subjected to drought stress. We evaluated the survival rate, total chlorophyll, total protein, carotenoids, proline, betaine glycine, soluble phenolic content, and antioxidant capacity every 3 days for 12 days. Symbiotic interaction was characterized by microscopy. Our results showed that the survival rate of inoculated plants was higher in 45% than the treatment without mycorrhizae. Total chlorophyll, protein, proline, betaine glycine content, and antioxidant capacity were increased in AMF inoculated plants. The soluble phenolic content was higher in non-inoculated plants than the treatment with mycorrhizae during the drought stress period. Microscopy showed the symbiotic relationship between plant and AMF. The early inoculation of 100 spores of G. intraradices per sugarcane plantlet during the acclimatization stage could represent a preconditioning advantage before transplanting into the field and establishing basic seedbeds.

Identification of genetic and biochemical mechanisms associated with heat shock and heat stress adaptation in grain amaranths.

Heat stress is poised to become a major factor negatively affecting plant performance worldwide. In terms of world food security, increased ambient temperatures are poised to reduce yields in cereals and other economically important crops. Grain amaranths are known to be productive under poor and/or unfavorable growing conditions that significantly affect cereals and other crops. Several physiological and biochemical attributes have been recognized to contribute to this favorable property, including a high water-use efficiency and the activation of a carbon starvation response. This study reports the behavior of the three grain amaranth species to two different stress conditions: short-term exposure to heat shock (HS) conditions using young plants kept in a conditioned growth chamber or long-term cultivation under severe heat stress in greenhouse conditions. The latter involved exposing grain amaranth plants to daylight temperatures that hovered around 50°C, or above, for at least 4 h during the day and to higher than normal nocturnal temperatures for a complete growth cycle in the summer of 2022 in central Mexico. All grain amaranth species showed a high tolerance to HS, demonstrated by a high percentage of recovery after their return to optimal growing conditions. The tolerance observed coincided with increased expression levels of unknown function genes previously shown to be induced by other (a)biotic stress conditions. Included among them were genes coding for RNA-binding and RNA-editing proteins, respectively. HS tolerance was also in accordance with favorable changes in several biochemical parameters usually induced in plants in response to abiotic stresses. Conversely, exposure to a prolonged severe heat stress seriously affected the vegetative and reproductive development of all three grain amaranth species, which yielded little or no seed. The latter data suggested that the usually stress-tolerant grain amaranths are unable to overcome severe heat stress-related damage leading to reproductive failure.

Tec1, a member of the TEA transcription factors family, is involved in virulence and basidiocarp development in Ustilago maydis / Tec1, un miembro de la familia de factores de transcripción TEA, está involucrado en la virulencia y el desarrollo de basidiocarpio en Ustilago maydis

The life cycle of Ustilago maydis involves alternation of a haploid saprophytic yeast-like stage and a dikaryotic hyphal virulent form. Under in vitro conditions, basidiocarps are formed. Analysis of the transcriptional network of basidiocarp formation revealed the possible involvement of a Tec transcription factor (Tec1, UMAG_02835) in the process. In some Ascomycota, Tec factors are involved in mycelial formation, pathogenesis, and interaction with other regulatory elements, but their role in Basidiomycota species is almost unknown. Accordingly, we proceeded to determine the role of this gene in U. maydis by its mutation. Tec1 was found to be a crucial factor for normal mating, basidiocarp development, and virulence, all of the functions related to the dikaryotic stage dependent of the b genes, whereas dimorphism and resistance to different stress conditions occurring in the haploid stage were not affected in tec1 mutants. The observation that mutants showed a low residual wild-type phenotype suggests the presence of a secondary mechanism that partially compensates the loss of Tec1.(AU)

Tec1, a member of the TEA transcription factors family, is involved in virulence and basidiocarp development in Ustilago maydis.

The life cycle of Ustilago maydis involves alternation of a haploid saprophytic yeast-like stage and a dikaryotic hyphal virulent form. Under in vitro conditions, basidiocarps are formed. Analysis of the transcriptional network of basidiocarp formation revealed the possible involvement of a Tec transcription factor (Tec1, UMAG_02835) in the process. In some Ascomycota, Tec factors are involved in mycelial formation, pathogenesis, and interaction with other regulatory elements, but their role in Basidiomycota species is almost unknown. Accordingly, we proceeded to determine the role of this gene in U. maydis by its mutation. Tec1 was found to be a crucial factor for normal mating, basidiocarp development, and virulence, all of the functions related to the dikaryotic stage dependent of the b genes, whereas dimorphism and resistance to different stress conditions occurring in the haploid stage were not affected in tec1 mutants. The observation that mutants showed a low residual wild-type phenotype suggests the presence of a secondary mechanism that partially compensates the loss of Tec1.

In Silico and Cellular Differences Related to the Cell Division Process between the A and B Races of the Colonial Microalga Botryococcus braunii.

Botryococcus braunii produce liquid hydrocarbons able to be processed into combustion engine fuels. Depending on the growing conditions, the cell doubling time can be up to 6 days or more, which is a slow growth rate in comparison with other microalgae. Few studies have analyzed the cell cycle of B. braunii. We did a bioinformatic comparison between the protein sequences for retinoblastoma and cyclin-dependent kinases from the A (Yamanaka) and B (Showa) races, with those sequences from other algae and Arabidopsis thaliana. Differences in the number of cyclin-dependent kinases and potential retinoblastoma phosphorylation sites between the A and B races were found. Some cyclin-dependent kinases from both races seemed to be phylogenetically more similar to A. thaliana than to other microalgae. Microscopic observations were done using several staining procedures. Race A colonies, but not race B, showed some multinucleated cells without chlorophyll. An active mitochondrial net was detected in those multinucleated cells, as well as being defined in polyphosphate bodies. These observations suggest differences in the cell division processes between the A and B races of B. braunii.

Natural or light-induced pigment accumulation in grain amaranths coincides with enhanced resistance against insect herbivory.

MAIN CONCLUSION: Increased resistance to insect herbivory in grain amaranth plants is associated with increased betalain pigmentation, either naturally acquired or accumulated in response to blue-red light irradiation. Betalains are water-soluble pigments characteristic of plants of the Caryophyllales order. Their abiotic stress-induced accumulation is believed to protect against oxidative damage, while their defensive function against biotic aggressors is scarce. A previous observation of induced betalain-biosynthetic gene expression in stressed grain amaranth plants led to the proposal that these pigments play a defensive role against insect herbivory. This study provided further support for this premise. First, a comparison of "green" and "red" Amaranthus cruentus phenotypes showed that the latter suffered less insect herbivory damage. Coincidentally, growth and vitality of Manduca sexta larvae were more severely affected when fed on red-leafed A. cruentus plants or on an artificial diet supplemented with red-leaf pigment extracts. Second, the exposure of A. cruentus and A. caudatus plants, having contrasting pigmentation phenotypes, to light enriched in the blue and red wavelength spectra led to pigment accumulation throughout the plant and to increased resistance to insect herbivory. These events were accompanied by the induced expression of known betalain-biosynthetic genes, including uncharacterized DODA genes believed to participate in this biosynthetic pathway in a still undefined way. Finally, transient co-expression of different combinations of betalain-biosynthetic genes in Nicotiana benthamiana led to detectable accumulation of betalamic acid and betanidin. This outcome supported the participation of certain AhDODA and other genes in the grain amaranth betalain-biosynthetic pathway.

Multi-Walled Carbon Nanotubes Improved Development during In Vitro Multiplication of Sugarcane (Saccharum spp.) in a Semi-Automated Bioreactor.

Carbon nanotubes play an important role in plant biotechnology due to their effects on the growth and differentiation of cells, tissues, organs, and whole plants. This study aimed to evaluate the effect of multi-walled carbon nanotubes (MWCNTs) during in vitro multiplication of sugarcane (Saccharum spp.) using a temporary immersion system. Morphological characterization of MWCNTs was carried out under a transmission electron microscope. Different concentrations (0, 50, 100, 200 mg L-1) of MWCNTs were added to Murashige and Skoog liquid culture medium in the multiplication stage. At 30 d of culture, number of shoots per explant, shoot length, number of leaves per shoot, total chlorophyll, dry matter percentage, carbon percentage, and macro- and micronutrient content were evaluated. Results showed an increase in the development of sugarcane shoots at concentrations of 100 and 200 mg L-1 MWCNT. Total chlorophyll content increased at concentrations of 50 and 100 mg L-1 MWCNT, whereas macro- and micronutrient content was variable at the different MWCNT concentrations. Results suggest a hormetic effect, characterized by stimulation at low concentrations. In conclusion, the use of low concentrations of MWCNTs had positive effects on development, total chlorophyll, carbon percentage, and macro- and micronutrient (N, Ca, S, Fe, Cu, Zn and Na) contents during in vitro multiplication of sugarcane and may have a potential use in other species of agricultural interest.

Voltage-Dependent Anion-Selective Channels and Other Mitochondrial Membrane Proteins Form Diverse Complexes in Beetroots Subjected to Flood-Induced Programmed Cell Death.

In plants, programmed cell death (PCD) is involved in both the development and the response to biotic and abiotic aggressions. In early stages of PCD, mitochondrial membranes are made permeable by the formation of permeability transition pores, whose protein composition is debated. Cytochrome c (cyt c) is then released from mitochondria, inducing the degradation of chromatin characteristic of PCD. Since flooding stress can produce PCD in several plant species, the first goal of this study was to know if flooding stress could be used to induce PCD in Beta vulgaris roots. To do this, 2-month-old beet plants were flood-stressed from 1 to 5 days, and the alterations indicating PCD in stressed beetroot cells were observed with a confocal fluorescence microscope. As expected, nuclei were deformed, and chromatin was condensed and fragmented in flooded beetroots. In addition, cyt c was released from mitochondria. After assessing that flood stress induced PCD in beetroots, the composition of mitochondrial protein complexes was observed in control and flood-stressed beetroots. Protein complexes from isolated mitochondria were separated by native gel electrophoresis, and their proteins were identified by mass spectrometry. The spectra count of three isoforms of voltage-dependent anion-selective channels (VDACs) increased after 1 day of flooding. In addition, the size of the complexes formed by VDAC was higher in flood-stressed beetroots for 1 day (∼200 kDa) compared with non-stressed ones (∼100 kDa). Other proteins, such as chaperonin CPN60-2, also formed complexes with different masses in control and flood-stressed beetroots. Finally, possible interactions of VDAC with other proteins were found performing a cluster analysis. These results indicate that mitochondrial protein complexes formed by VDAC could be involved in the process of PCD in flood-stressed beetroots. Data are available via ProteomeXchange with identifier PXD027781.

Post-synthesis nanostructuration of BSA-Capsaicin nanoparticles generated by sucrose excipient.

In the pharmaceutical industry nano-hydrocolloid systems frequently coalesce or present nanoparticle aggregation after a long storage periods. Besides, the lyophilization process used to dry nanoparticles (NPs) produces loss of their original properties after dispersion. In this work we evaluated the effect on morphology and physicochemical properties of different protective excipients during drying of bovine serum albumin (BSA) NPs loaded with different concentrations of capsaicin. Capsaicin concentrations of 0, 812, 1625, 2437, and 3250 µg mL-1 were used; subsequently, NPs were dried with deionized water (DW), NaCl (DN), sucrose (DS), and not dried (ND). We found that ND, DW, and DN treatments showed a negative effect on the NPs properties; while, DS reduced the aggregation and produced the formation of isolated nanoparticles at higher concentrations of capsaicin (3250 µg mL-1), improving their circular shape, morphometrical parameters, and ζ-potential. The stability of the BSA-capsaicin NPs was associated to complex capsaicin/amino acid/water, in which GLY/GLN, ALA/HIS, ARG, THR, TYR, and Iso/CYS amino acids are involved in the restructuration of capsaicin molecules into the surface of nanoparticles during the drying process. The secondary nanostructuration in the post-synthesis stage can improve the molecular stability of the particles and the capacity of entrapping hydrophobic drugs, like capsaicin.

Acid pH Strategy Adaptation through NRG1 in Ustilago maydis.

The role of the Ustilago maydis putative homolog of the transcriptional repressor ScNRG1, previously described in Saccharomyces cerevisiae, Candida albicans and Cryptococcus neoformans, was analyzed by means of its mutation. In S. cerevisiae this gene regulates a set of stress-responsive genes, and in C. neoformans it is involved in pathogenesis. It was observed that the U. maydisNRG1 gene regulates several aspects of the cell response to acid pH, such as the production of mannosyl-erythritol lipids, inhibition of the expression of the siderophore cluster genes, filamentous growth, virulence and oxidative stress. A comparison of the gene expression pattern of the wild type strain versus the nrg1 mutant strain of the fungus, through RNA Seq analyses, showed that this transcriptional factor alters the expression of 368 genes when growing at acid pH (205 up-regulated, 163 down-regulated). The most relevant genes affected by NRG1 were those previously reported as the key ones for particular cellular stress responses, such as HOG1 for osmotic stress and RIM101 for alkaline pH. Four of the seven genes included WCO1 codifying PAS domain ( These has been shown as the key structural motif involved in protein-protein interactions of the circadian clock, and it is also a common motif found in signaling proteins, where it functions as a signaling sensor) domains sensors of blue light, two of the three previously reported to encode opsins, one vacuolar and non-pH-responsive, and another one whose role in the acid pH response was already known. It appears that all these light-reactive cell components are possibly involved in membrane potential equilibrium and as virulence sensors. Among previously described specific functions of this transcriptional regulator, it was found to be involved in glucose repression, metabolic adaptation to adverse conditions, cellular transport, cell rescue, defense and interaction with an acidic pH environment.

Highly Branched Neo-Fructans (Agavins) Attenuate Metabolic Endotoxemia and Low-Grade Inflammation in Association with Gut Microbiota Modulation on High-Fat Diet-Fed Mice.

Highly branched neo-fructans (agavins) are natural prebiotics found in Agave plants, with a large capacity to mitigate the development of obesity and metabolic syndrome. Here, we investigated the impact of agavins intake on gut microbiota modulation and their metabolites as well as their effect on metabolic endotoxemia and low-grade inflammation in mice fed high-fat diet. Mice were fed with a standard diet (ST) and high-fat diet (HF) alone or plus an agavins supplement (HF+A) for ten weeks. Gut microbiota composition, fecal metabolite profiles, lipopolysaccharides (LPS), pro-inflammatory cytokines, and systemic effects were analyzed. Agavins intake induced substantial changes in gut microbiota composition, enriching Bacteroides, Parabacteroides, Prevotella, Allobaculum, and Akkermansia genus (LDA > 3.0). l-leucine, l-valine, uracil, thymine, and some fatty acids were identified as possible biomarkers for this prebiotic supplement. As novel findings, agavins supplementation significantly decreased LPS and pro-inflammatory (IL-1α, IL-1ß, and TNF-α; p < 0.05) cytokines levels in portal vein. In addition, lipid droplets content in the liver and adipocytes size also decreased with agavins consumption. In conclusion, agavins supplementation mitigate metabolic endotoxemia and low-grade inflammation in association with gut microbiota regulation and their metabolic products, thus inducing beneficial responses on metabolic disorders in high-fat diet-fed mice.

Cell death in Ustilago maydis: comparison with other fungi and the effect of metformin and curcumin on its chronological lifespan.

Ustilago maydis is a Basidiomycota fungus, in which very little is known about its mechanisms of cell survival and death. To date, only the role of metacaspase1, acetate and hydrogen peroxide as inducers of cell death has been investigated. In the present work, we analyzed the lifespan of U. maydis compared with other species like Sporisorium reilianum, Saccharomyces cerevisiae and Yarrowia lipolytica, and we observed that U. maydis has a minor lifespan. We probe the addition of low concentrations metformin and curcumin to the culture media, and we observed that both prolonged the lifespan of U. maydis, a result observed for the first time in a phytopathogen fungus. However, higher concentrations of curcumin were toxic for the cells, and interestingly induced the yeast-to-mycelium dimorphic transition. The positive effect of metformin and curcumin appears to be related to an inhibition of the mechanistic Target of Rapamycin (mTOR) pathway, increase expression of autophagy genes and reducing of reactive oxygen species. These data indicate that U. maydis may be a eukaryotic model organism to elucidate the molecular mechanism underlying apoptotic and necrosis pathways, and the lifespan increase caused by metformin and curcumin.

Quantum Dot Labelling of Tepary Bean (Phaseolus acutifolius) Lectins by Microfluidics.

Lectins are bioactive proteins with the ability to recognize cell membrane carbohydrates in a specific way. Diverse plant lectins have shown diagnostic and therapeutic potential against cancer, and their cytotoxicity against transformed cells is mediated through the induction of apoptosis. Previous works have determined the cytotoxic activity of a Tepary bean (Phaseolus acutifolius) lectin fraction (TBLF) and its anti-tumorigenic effect on colon cancer. In this work, lectins from the TBLF were additionally purified by ionic-exchange chromatography. Two peaks with agglutination activity were obtained: one of them was named TBL-IE2 and showed a single protein band in two-dimensional electrophoresis; this one was thus selected for coupling to quantum dot (QD) nanoparticles by microfluidics (TBL-IE2-QD). The microfluidic method led to low sample usage, and resulted in homogeneous complexes, whose visualization was achieved using multiphoton and transmission electron microscopy. The average particle size (380 nm) and the average zeta potential (-18.51 mV) were determined. The cytotoxicity of the TBL-IE2 and TBL-IE2-QD was assayed on HT-29 colon cancer cells, showing no differences between them (p ≤ 0.05), where the LC50 values were 1.0 × 10-3 and 1.7 × 10-3 mg/mL, respectively. The microfluidic technique allowed control of the coupling between the QD and the protein, substantially improving the labelling process, providing a rapid and efficient method that enabled the traceability of lectins. Future studies will focus on the potential use of the QD-labelled lectin to recognize tumor tissues.

Generation of BSA-capsaicin Nanoparticles and Their Hormesis Effect on the Rhodotorula mucilaginosa Yeast.

Capsaicin is a chemical compound found in pungent chili peppers (Capsicum spp.). In biotechnology, capsaicin has been proposed as a pathogen control; however, its low solubility in water and high instability limits its uses. The aim of this work was to study the effect of high concentrations of capsaicin on the synthesis of nanoparticles and to evaluate their inhibitory effect on the growth of Rhodotorula mucilaginosa yeast. Bovine serum albumin (BSA)-capsaicin nanoparticles were formulated at 0, 16.2, 32.5, 48.7 and 65.0 µg of capsaicin per mg of BSA. Nanoparticle properties were evaluated and they were added to cultures of R. mucilaginosa to quantify their effect on cell viability. We found that increased capsaicin levels caused several changes to the physicochemical parameters, probably due to changes in the hydrophobicity sites of the albumin during the nanostructuration. The administration of nanoparticles to cultures of R. mucilaginosa produced a maximal viability with nanoparticles at 16.2 µg/mg; on the contrary, nanoparticles at 65.0 µg/mg caused maximal cell death. R. mucilaginosa cells displayed a hormesis effect in response to the nanoparticle dose concentration. The nanoparticles showed different responses during the uptake process, probably as a consequence of the nanostructural properties of capsaicin in the BSA molecules.

Exposure of stevia (Stevia rebaudiana B.) to silver nanoparticles in vitro: transport and accumulation.

The impact of nanotechnology in the field of agricultural sciences creates the need to study in greater detail the effect of products offering nanoparticles for application in plant species of agricultural interest. The objective of this study was to determine the response of stevia (Stevia rebaudiana B.) in vitro to different concentrations of AgNPs (silver nanoparticles), as well as to characterize and identify their absorption, translocation and accumulation mechanisms. Nodal segments of stevia grown in MS medium supplemented with AgNPs (0,12.5, 25, 50,100 and 200 mg L-1) were used. After 30 days of in vitro shoot proliferation, the number of shoots per explant, shoot length, chlorophyll content, dry matter content and the metallic silver (Ag) content of the plants were quantified. In addition, characterization, transport and accumulation of silver nanoparticles were performed by microscopic analysis. AgNPs were shown to be present in epidermal stem cells, within vascular bundles and in intermembrane spaces. In leaves, they were observed in ribs and stomata. The current and future use of AgNPs in agricultural sciences opens up the possibility of studying their effects on different plant species.

Non-destructive Plant Morphometric and Color Analyses Using an Optoelectronic 3D Color Microscope.

Gene function discovery in plants, as other plant science quests, is aided by tools that image, document, and measure plant phenotypes. Tools that acquire images of plant organs and tissues at the microscopic level have evolved from qualitative documentation tools, to advanced tools where software-assisted analysis of images extracts quantitative information that allows statistical analyses. They are useful to perform morphometric studies that describe plant physical characteristics and quantify phenotypes, aiding gene function discovery. In parallel, non-destructive, versatile, robust, and user friendly technologies have also been developed for surface topography analysis and quality control in the industrial manufacture sector, such as optoelectronic three-dimensional (3D) color microscopes. These microscopes combine optical lenses, electronic image sensors, motorized stages, graphics engines, and user friendly software to allow the visualization and inspection of objects of diverse sizes and shapes from different angles. This allow the integration of different automatically obtained images along the Z axis of an object, into a single image with a large depth-of-field, or a 3D model in color. In this work, we explored the performance of an optoelectronic microscope to study plant morphological phenotypes and plant surfaces in different model species. Furthermore, as a "proof-of-concept," we included the phenotypic characterization (morphometric analyses at the organ level, color, and cell size measurements) of Arabidopsis mutant leaves. We found that the microscope tested is a suitable, practical, and fast tool to routinely and precisely analyze different plant organs and tissues, producing both high-quality, sharp color images and morphometric and color data in real time. It is fully compatible with live plant tissues (no sample preparation is required) and does not require special conditions, high maintenance, nor complex training. Therefore, though barely reported in plant scientific studies, optoelectronic microscopes should emerge as convenient and useful tools for phenotypic characterization in plant sciences.

Starch accumulation is associated with active growth in A. tequilana.

Transcriptome analysis of different tissues and developmental stages of A. tequilana plants led to the identification of full length cDNAs and the corresponding amino acid sequences for enzymes involved in starch metabolism in this species. Comparison with sequences from other species confirmed the identities of putative A. tequilana starch metabolism genes and uncovered differences in the evolutionary patterns of these genes between gramineous and non-gramineous monocotyledons. In silico expression patterns showed high levels of expression of starch metabolism genes in shoot apical meristem tissue and histological studies showed the presence of starch in leaf primordia surrounding the shoot apical meristem and in the primary thickening meristem of the stem. Starch was also found to accumulate significantly in developing floral organs and immature embryos. Low levels of starch were observed overall in leaf tissue with the exception of stomatal guard cells where starch was abundant. In root tissue, starch was only observed in statoliths at the root tip. A. tequilana starch grains were found to be small in comparison to other species and have an almost spherical form. The data for gene expression and histological localization are consistent with a role for starch as a transient carbohydrate store for actively growing tissues in A. tequilana.

Transcriptional profiling of the CAM plant Agave salmiana reveals conservation of a genetic program for regeneration.

In plants, the best characterized plant regeneration process is de novo organogenesis. This type of regeneration is characterized by the formation of a multicellular structure called callus. Calli are induced via phytohormone treatment of plant sections. The callus formation in plants like Agave species with Crassulacean Acid Metabolism (CAM) is poorly studied. In this study, we induced callus formation from Agave salmiana leaves and describe cell arrangement in this tissue. Moreover, we determined and analyzed the transcriptional program of calli, as well as those of differentiated root and leaf tissues, by using RNA-seq. We were able to reconstruct 170,844 transcripts of which 40,644 have a full Open Reading Frame (ORF). The global profile obtained by Next Generation Sequencing (NGS) reveals that several callus-enriched protein coding transcripts are orthologs of previously reported factors highly expressed in Arabidopsis calli. At least 62 genes were differentially expressed in Agave calli, 50 of which were up-regulated. Several of these are actively involved in the perception of, and response to, auxin and cytokinin. Not only are these the first results for the A. salmiana callus, but they provide novel data from roots and leaves of this Agave species, one of the largest non-tree plants in nature.

AhDGR2, an amaranth abiotic stress-induced DUF642 protein gene, modifies cell wall structure and composition and causes salt and ABA hyper-sensibility in transgenic Arabidopsis.

MAIN CONCLUSION: An amaranth DGR gene, induced under abiotic stress, modifies cell wall structure and causes hypersensitivity to ABA and salt when overexpressed in Arabidopsis. DUF642 is a highly conserved plant-specific family of unknown cell wall-associated proteins. The AhDGR2 gene, coding for a DUF642 protein, was significantly induced in grain amaranth (Amaranthus hypochondriacus) plants subjected to water-deficit and salinity stress, thereby suggesting its participation in abiotic stress tolerance in this plant. A role in development was also inferred from the higher AhDGR2 expression rates detected in young tissues. Subsequent overexpression of AhDGR2 in transgenic Arabidopsis plants (OE-AhDGR2) supported its possible role in development processes. Thus, OE-AhDGR2 plants generated significantly longer roots when grown in normal MS medium. However, they showed a hypersensitivity to increasing concentrations of abscisic acid or NaCl in the medium, as manifested by shorter root length, smaller and slightly chlorotic rosettes, as well as highly reduced germination rates. Contrary to expectations, OE-AhDGR2 plants were intolerant to abiotic stress. Moreover, cell walls in transgenic plants were thinner, in leaves, and more disorganized, in roots, and had significantly modified pectin levels. Lower pectin methylesterase activity detected in leaves of OE-AhDGR2 plants, but not in roots, was contrary to previous reports associating DUF642 proteins and decreased pectin esterification levels in cell walls. Nonetheless, microarray data identified candidate genes whose expression levels explained the phenotypes observed in leaves of OE-AhDGR2 plants, including several involved in cell wall integrity and extension, growth and development, and resistance to abiotic stress. These results support the role of DUF642 proteins in cell wall-related processes and offer novel insights into their possible role(s) in plants.

Naphthalene Acetic Acid Potassium Salt (NAA-K+) Affects Conidial Germination, Sporulation, Mycelial Growth, Cell Surface Morphology, and Viability of Fusarium oxysporum f. sp. radici-lycopersici and F. oxysporum f. sp. cubense in Vitro.

The response to exogenous addition of naphthalene acetic acid potassium salt (NAA-K+) to Fusarium oxysporum f. sp radici-lycopersici ATCC 60095 and F. oxysporum f. sp. cubense isolated from Michoacan Mexico soil is reported. The in vitro study showed that NAA-K+ might be effective in the control of Fusarium oxysporum. Exogenous application of NAA-K+ affected both spores and mycelium stages of the fungi. Viability testing using acridine orange and propidium iodide showed that NAA-K+ possesses fungal killing properties, doing it effectively in the destruction of conidia of this phytopathogenic fungi. Analysis of treated spores by scanning electron microscopy showed changes in the shape factor and fractal dimension. Moreover, NAA-K+ repressed the expression of brlA and fluG genes. The results disclosed here give evidence of the use of this synthetic growth factor as a substance of biocontrol that presents advantages, and the methods of application in situ should be explored.