La variación genética de maíz (Zea mays ssp. mays L.) en México ha sido estudiada especialmente en el centro-sur del país. El estado de Sinaloa (primero en producción) posee 23% de la variación ...genética racial nacional, pero su evaluación es escasa. Recolectamos 144 muestras de maíz (Tuxpeño Norteño, Vandeño, Onaveño, Elotero de Sinaloa, Tabloncillo, Tabloncillo Perla, Bofo, Jala, Blando de Sonora, Chapalote, Dulcillo del Noroeste y Reventador) en distintos puntos del estado con el objetivo de describir las características morfológicas y agronómicas relevantes para determinar un patrón de agrupación. Las accesiones fueron evaluadas en dos ambientes con un diseño de látice simple 12·12, analizando 27 variables. El ANDEVA detectó diferencias significativas entre accesiones (todas las variables), interacción genotipo · ambiente (anchura/longitud del grano) y ambientes en la espiga (longitud del tramo ramificado, número de ramificaciones primarias y longitud de la rama central), mazorca (diámetro/ longitud, longitud del pedúnculo y de mazorca) y grano (volumen y peso/volumen). Los tres primeros componentes principales (CP) explicaron 64% de la varianza, donde las variables: número de hojas, diámetro y longitud de la mazorca; la anchura y espesor de grano; anchura/longitud del grano y floración; son las más importantes. La representación gráfica de los CP1 y CP2 reveló seis grupos y la de conglomerados cinco. Algunas accesiones poseían características compartidas con más de un grupo racial y su posición fue cercana a la de quienes compartían características. Se confirma una amplia diversidad genética de maíces nativos en Sinaloa.
During the endosymbiosis formed between plants and arbuscular mycorrhizal (AM) fungi, the root cortical cells are colonized by branched hyphae called arbuscules, which function in nutrient exchange ...with the plant 1. Despite their positive function, arbuscules are ephemeral structures, and their development is followed by a degeneration phase, in which the arbuscule and surrounding periarbuscular membrane and matrix gradually disappear from the root cell 2, 3. Currently, the root cell’s role in this process and the underlying regulatory mechanisms are unknown. Here, by using a Medicago truncatula pt4 mutant in which arbuscules degenerate prematurely 4, we identified arbuscule degeneration-associated genes, of which 38% are predicted to encode secreted hydrolases, suggesting a role in disassembly of the arbuscule and interface. Through RNAi and analysis of an insertion mutant, we identified a symbiosis-specific MYB-like transcription factor (MYB1) that suppresses arbuscule degeneration in mtpt4. In myb1, expression of several degeneration-associated genes is reduced. Conversely, in roots constitutively overexpressing MYB1, expression of degeneration-associated genes is increased and subsequent development of symbiosis is impaired. MYB1-regulated gene expression is enhanced by DELLA proteins and is dependent on NSP1 5, but not NSP2 6. Furthermore, MYB1 interacts with DELLA and NSP1. Our data identify a transcriptional program for arbuscule degeneration and reveal that its regulators include MYB1 in association with two transcriptional regulators, NSP1 and DELLA, both of which function in preceding phases of the symbiosis. We propose that the combinatorial use of transcription factors enables the sequential expression of transcriptional programs for arbuscule development and degeneration.
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•A transcriptional program associated with arbuscule degeneration during AM symbiosis•Arbuscule degeneration-associated genes encoding hydrolases are regulated by MYB1•della double and triple mutants reveal that DELLAs influence arbuscule degeneration•MYB1-regulated gene expression requires NSP1 and is enhanced by DELLAs
During AM symbiosis, the root cortical cells construct and later disassemble a membrane and matrix around the fungal symbiont. Floss et al. identify a transcriptional program associated with arbuscule degeneration and reveal that expression of degeneration-associated hydrolase genes is regulated by MYB1 in association with NSP1 and DELLAs.
ABSTRACT
Bacterial chitinases are a subject of intense scientific research due to their biotechnological applications, particularly their use as biological pesticides against phytopathogenic fungi as ...a green alternative to avoid the use of synthetic pesticides. Bacillus cereus sensu lato B25 is a rhizospheric bacterium that is a proven antagonist of Fusarium verticillioides, a major fungal pathogen of maize. This bacterium produces two chitinases that degrade the fungal cell wall and inhibit its growth. In this work, we used a heterologous expression system to purify both enzymes to investigate their biochemical traits in terms of Km, Vmax, optimal pH and temperature. ChiA and ChiB work as exochitinases, but ChiB exhibited a dual substrate activity and it is also an endochitinase. In this work, the direct addition of these chitinases inhibited fungal conidial germination and therefore they may play a major role in the antagonism against F. verticillioides.
Bacillus cereus sensu lato strain B25 produces two chitinases: ChiA with endo- and ChiB with endo-/exo-chitinase activity, both inhibiting conidial germination of the maize fungal pathogen Fusarium verticillioides.
Plants associated with arbuscular mycorrhizal fungi (AMF) increase their tolerance to arsenic-polluted soils. This study aims to investigate the genes involved in the AMF molecular response to ...arsenic pollution. Genes encoding proteins involved in arsenic metabolism were identified and their expression assessed by PCR or RT-qPCR. The As-inducible gene GiArsA (R. irregularis ABC ATPase component of the ArsAB arsenite efflux pump) and two new genes, an arsenate/arsenite permease component of ArsAB (RiArsB) and a methyltransferase type 11 (RiMT-11) were induced when arsenate was added to two-compartment in vitro monoxenic cultures of R. irregularis-transformed carrot roots. RiArsB and RiMT-11 expression in extraradical hyphae in response to arsenate displayed maximum induction 4–6 h after addition of 350 μM arsenate. Their expression was also detected in colonized root tissues grown in pots, or in the root-fungus compartment of two-compartment in vitro systems. We used a Medicago truncatula double mutant (mtpt4/mtpt8) to demonstrate that RiMT-11 and RiArsB transcripts accumulate in response to the addition of arsenate but not in response to phosphate. These results suggest that these genes respond to arsenate addition regardless of non-functional Pi symbiotic transport, and that RiMT-11 may be involved in arsenate detoxification by methylation in AMF-colonized tissues.
Fusarium species belonging to the Fusarium fujikuroi species complex (FFSC) are associated with maize in northern Mexico and cause Fusarium ear and root rot. In order to assess the diversity of FFSC ...fungal species involved in this destructive disease in Sinaloa, Mexico, a collection of 108 fungal isolates was obtained from maize plants in 2007–2011. DNA sequence analysis of the calmodulin and elongation factor 1α genes identified four species: Fusarium verticillioides, F. nygamai, F. andiyazi and F. thapsinum (comprising 79, 23, 4 and 2 isolates, respectively). Differential distribution of Fusarium species in maize organs was observed, that is F. verticillioides was the most frequently isolated species from maize seeds, while F. nygamai predominated on maize roots. Mixed infections with F. verticillioides/F. thapsinum and F. verticillioides/F. nygamai were detected in maize seeds and roots, respectively. Pathogenicity assay demonstrated the ability of the four species to infect maize seedlings and induce different levels of disease severity, reflecting variation in aggressiveness, plant height and root biomass. Isolates of F. verticillioides and F. nygamai were the most aggressive. These species were able to colonize all root tissues, from the epidermis to the vascular vessels, while infection by F. andiyazi and F. thapsinum was restricted to the epidermis and adjacent cortical cells. This is the first report of F. nygamai, F. andiyazi and F. thapsinum infecting maize in Mexico and co‐infecting with F. verticillioides. Mixed infections should be taken into consideration due to the production and/or accumulation of diverse mycotoxins in maize grain.
The majority of vascular flowering plants are able to form symbiotic associations with arbuscular mycorrhizal fungi. These symbioses, termed arbuscular mycorrhizas, are mutually beneficial, and the ...fungus delivers phosphate to the plant while receiving carbon. In these symbioses, phosphate uptake by the arbuscular mycorrhizal fungus is the first step in the process of phosphate transport to the plant. Previously, we cloned a phosphate transporter gene involved in this process. Here, we analyze the expression and regulation of a phosphate transporter gene (GiPT) in the extra-radical mycelium of the arbuscular mycorrhizal fungus Glomus intraradices during mycorrhizal association with carrot or Medicago truncatula roots. These analyses reveal that GiPT expression is regulated in response to phosphate concentrations in the environment surrounding the extra-radical hyphae and modulated by the overall phosphate status of the mycorrhiza. Phosphate concentrations, typical of those found in the soil solution, result in expression of GiPT. These data imply that G. intraradices can perceive phosphate levels in the external environment but also suggest the presence of an internal phosphate sensing mechanism.
Bacillus
sp. B25 is an effective biocontrol agent against the maize pathogenic fungus
Fusarium verticillioides
(
Fv
). Previous in vitro assays have shown that B25 has protease, glucanase, and ...chitinase activities and siderophores production; however, specific mechanisms by which B25 controls
Fv
are still unknown. To determine the genetic traits involved in biocontrol, B25 genome was sequenced and analyzed. B25 genome is composed of 5,113,413 bp and 5251 coding genes. A multilocus phylogenetic analysis (MLPA) suggests that B25 is closely related to the
Bacillus cereus
group and a high percentage (70–75%) of the genetic information is conserved between B25 and related strains, which include most of the genes associated to fungal antagonism. Some of these genes are shared with some biocontrol agents of the
Bacillus
genus and less with
Pseudomonas
and
Serratia
strains. We performed a genomic comparison between B25 and five
Bacillus
spp.,
Pseudomonas
and
Serratia
strains. B25 contains genes involved in a wide variety of antagonistic mechanisms including chitinases, glycoside hydrolases, siderophores, antibiotics, and biofilm production that could be implicated in root colonization. Also, 24 genomic islands and 3 CRISPR sequences were identified in the B25 genome. This is the first comparative genome analysis between strains belonging to the
B. cereus
group and biocontrol agents of phytopathogenic fungi. These results are the starting point for further studies on B25 gene expression during its interaction with
Fv
.
•Pecan nut, as part of a high fat diet, prevented hyperleptinemia, fat accumulation and liver lipid peroxidation.•Pecan nut stimulated hepatic expression of LDL receptor and SREBP 1c mRNA.•Pecan ...polyphenols stimulated hepatic expression of LXR alpha mRNA.•Stronger effects were produced by the whole pecan and not by the isolated oil or polyphenol fractions.
Tree nuts such as pecans (Carya illinoinensis) contain mostly oil but are also a source of polyphenols. Nut consumption has been linked to a reduction in serum lipid levels and oxidative stress. These effects have been attributed to the oil while overlooking the potential contribution of the polyphenols. Because the evidence regarding each fraction’s bioactivity is scarce, we administered high-fat (HF) diets to male Wistar rats, supplementing them with pecan oil (HF+PO), pecan polyphenols (HF+PP) or whole pecans (HF+WP), and analysed the effects of each fraction. The HF diet increased the serum leptin and total cholesterol (TC) with respect to the control levels. The HF+WP diet prevented hyperleptinemia and decreased the TC compared with the control. The HF+WP diet upregulated the hepatic expression of apolipoprotein B and LDL receptor mRNAs with respect to the HF levels. The HF+PO diet reduced the level of triacylglycerols compared with the control. The HF+PP diet stimulated the hepatic expression of liver X receptor alpha mRNA. The HF+WP diet increased the activities of hepatic catalase, glutathione peroxidase and glutathione S transferase compared with the control, and decreased the degree of lipid peroxidation compared with the HF diet. The most bioactive diet was the WP diet.
This study evaluated the effect of
Pediococcus pentosaceus and
Staphylococcus hemolyticus as probiotics in whiteleg shrimp
Litopenaeus vannamei naturally infected with WSSV and IHHNV. All bacteria ...were isolated from the gut of wild brown shrimp (
Farfantepenaeus californiensis). Presumptive lactic acid bacteria were characterized for hemolytic and enzymatic activity, hydrophobicity, growth, and molecular identification. Two mixtures of four isolates were tested and their effect measured on the hemocyte number, survival, and prevalence of WSSV and IHHNV. Each mixture was applied at two different concentrations in a 15-day bioassay with shrimp naturally infected with WSSV and IHHNV as determined by single and/or nested PCR. In the treated animals total hemocyte count and survival were similar to control group. All shrimp fed with bacterial mixtures showed a decrease in the prevalence of WSSV but not IHHNV. The results obtained in this preliminary study revealed a protective effect of the two bacterial mixtures against WSSV latent infections.
► This study evaluated the effect of probiotics in
Litopenaeus vannamei. ► Probiotics tested in shrimp have a beneficial effect against WSSV but not IHHNV. ► Probiotics are good candidates to be used as feed additives in shrimp culture.
Bacterial transformation is a crucial step in the genetic manipulation of a bacterium. However, Gram-positive bacteria are difficult to transform and consequently many different methodologies have ...been developed. Here, we examined the transformation efficiencies of an electroporation protocol by varying three main factors: the composition of the electroporation buffer, the strength of the electric pulse, and the composition of the recovery media. Overall, transformation efficiency was enhanced when we prepared the electrocompetent cells at room temperature instead of an ice-cold temperature. The protocol detailed in this work was demonstrated to be applicable to another B. cereus strain and two other Bacillus species, and has the potential to be applied to other undomesticated Gram-positive and/or rhizospheric bacterial strains that are difficult to transform using current methodologies.
•Protocol for rhizospheric Bacillus cereus was developed.•Bacillus cereus B25 requires non-methylated DNA for transformation.•Efficiency of several electroporation protocols was analyzed.
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