Instituto Tecnológico Superior de Irapuato

Pigments are present in all living matter and provide attractive colors and play basic roles in the development of organisms. Human beings, like most animals, come in contact with their surroundings through color, and things can or cannot be acceptable based on their color characteristics. This review presents the basic information about pigments focusing attention on the natural ones; it emphasizes the principal plant pigments: carotenoids, anthocyanins, and betalains. Special considerations are given to their salient characteristics; to their biosynthesis, taking into account the biochemical and molecular biology information generated in their elucidation; and to the processing and stability properties of these compounds as food colorants.

Anthropogenic trade and development have broken down dispersal barriers, facilitating the spread of diseases that threaten Earth's biodiversity. We present a global, quantitative assessment of the amphibian chytridiomycosis panzootic, one of the most impactful examples of disease spread, and demonstrate its role in the decline of at least 501 amphibian species over the past half-century, including 90 presumed extinctions. The effects of chytridiomycosis have been greatest in large-bodied, range-restricted anurans in wet climates in the Americas and Australia. Declines peaked in the 1980s, and only 12% of declined species show signs of recovery, whereas 39% are experiencing ongoing decline. There is risk of further chytridiomycosis outbreaks in new areas. The chytridiomycosis panzootic represents the greatest recorded loss of biodiversity attributable to a disease.

Mushrooms have been consumed since earliest history; ancient Greeks believed that mushrooms provided strength for warriors in battle, and the Romans perceived them as the "Food of the Gods." For centuries, the Chinese culture has treasured mushrooms as a health food, an "elixir of life." They have been part of the human culture for thousands of years and have considerable interest in the most important civilizations in history because of their sensory characteristics; they have been recognized for their attractive culinary attributes. Nowadays, mushrooms are popular valuable foods because they are low in calories, carbohydrates, fat, and sodium: also, they are cholesterol-free. Besides, mushrooms provide important nutrients, including selenium, potassium, riboflavin, niacin, vitamin D, proteins, and fiber. All together with a long history as food source, mushrooms are important for their healing capacities and properties in traditional medicine. It has reported beneficial effects for health and treatment of some diseases. Many nutraceutical properties are described in mushrooms, such as prevention or treatment of Parkinson, Alzheimer, hypertension, and high risk of stroke. They are also utilized to reduce the likelihood of cancer invasion and metastasis due to antitumoral attributes. Mushrooms act as antibacterial, immune system enhancer and cholesterol lowering agents; additionally, they are important sources of bioactive compounds. As a result of these properties, some mushroom extracts are used to promote human health and are found as dietary supplements.

Phosphorus, one of the essential elements for plants, is often a limiting nutrient because of its low availability and mobility in soils. Significant changes in plant morphology and biochemical processes are associated with phosphate (Pi) deficiency. However, the molecular bases of these responses to Pi deficiency are not thoroughly elucidated. Therefore, a comprehensive survey of global gene expression in response to Pi deprivation was done by using Arabidopsis thaliana whole genome Affymetrix gene chip (ATH1) to quantify the spatio-temporal variations in transcript abundance of 22,810 genes. The analysis revealed a coordinated induction and suppression of 612 and 254 Pi-responsive genes, respectively. The functional classification of some of these genes indicated their involvement in various metabolic pathways, ion transport, signal transduction, transcriptional regulation, and other processes related to growth and development. This study is a detailed analysis of Pi starvation-induced changes in gene expression of the entire genome of Arabidopsis correlated with biochemical processes. The results not only enhance our knowledge about molecular processes associated with Pi deficiency, but also facilitate the identification of key molecular determinants for improving Pi use by crop species.

The postembryonic developmental program of the plant root system is plastic and allows changes in root architecture to adapt to environmental conditions such as water and nutrient availability. Among essential nutrients, phosphorus (P) often limits plant productivity because of its low mobility in soil. Therefore, the architecture of the root system may determine the capacity of the plant to acquire this nutrient. We studied the effect of P availability on the development of the root system in Arabidopsis. We found that at P-limiting conditions (<50 microM), the Arabidopsis root system undergoes major architectural changes in terms of lateral root number, lateral root density, and primary root length. Treatment with auxins and auxin antagonists indicate that these changes are related to an increase in auxin sensitivity in the roots of P-deprived Arabidopsis seedlings. It was also found that the axr1-3, axr2-1, and axr4-1 Arabidopsis mutants have normal responses to low P availability conditions, whereas the iaa28-1 mutant shows resistance to the stimulatory effects of low P on root hair and lateral root formation. Analysis of ethylene signaling mutants and treatments with 1-aminocyclopropane-1-carboxylic acid showed that ethylene does not promote lateral root formation under P deprivation. These results suggest that in Arabidopsis, auxin sensitivity may play a fundamental role in the modifications of root architecture by P availability.

Many plants interact with carnivores as an indirect defence against herbivores. The release of volatile organic compounds (VOCs) and the secretion of extrafloral nectar (EFN) are induced by insect feeding, a response that is mediated by the plant hormone, jasmonic acid. Although VOCs mainly attract predatory mites and parasitic wasps, while EFN mainly attracts ants, many more animal-plant interactions are influenced by these two traits. Other traits involved in defensive tritrophic interactions are cellular food bodies and domatia, which serve the nutrition and housing of predators. They are not known to respond to herbivory, while food body production can be induced by the presence of the mutualists. Interactions among the different defensive traits, and between them and other biotic and abiotic factors exist on the genetic, physiological, and ecological levels, but so far remain understudied. Indirect defences are increasingly being discussed as an environmentally-friendly crop protection strategy, but much more knowledge on their fitness effects under certain environmental conditions is required before we can understand their ecological and evolutionary relevance, and before tritrophic interactions can serve as a reliable tool in agronomy.

Aluminum when in soluble form, as found in acidic soils that comprise about 40 percent of the world's arable land, is toxic to many crops. Organic acid excretion has been correlated with aluminum tolerance in higher plants. Overproduction of citrate was shown to result in aluminum tolerance in transgenic tobacco (Nicotiana tabacum) and papaya (Carica papaya) plants.

When growing under limiting phosphate (P) conditions, Arabidopsis thaliana plants show dramatic changes in root architecture, including a reduction in primary root length, increased formation of lateral roots and greater formation of root hairs. Here we report that primary root growth inhibition by low P is caused by a shift from an indeterminate to a determinate developmental program. In the primary root, the low P-induced determinate growth program initiates with a reduction of cell elongation followed by the progressive loss of meristematic cells. At later stages, cell proliferation ceases and cell differentiation takes place at the former cell elongation and meristematic regions of the primary root. In low P, not only the primary but also almost all mature lateral roots enter the determinate developmental program. Kinetic studies of expression of the cell cycle marker CycB1;1:uidA and the quiescent center (QC) identity marker QC46:GUS showed that in low P conditions, reduction in proliferation in the primary root was preceded by alterations in the QC. These results suggest that in Arabidopsis, P limitation can induce a determinate root developmental program that plays an important role in altering root system architecture and that the QC could act as a sensor of environmental signals.

Candida albicans is one of the most important opportunistic pathogenic fungi. Weakening of the defense mechanisms of the host, and the ability of the microorganism to adapt to the environment prevailing in the host tissues, turn the fungus from a rather harmless saprophyte into an aggressive pathogen. The disease, candidiasis, ranges from light superficial infections to deep processes that endanger the life of the patient. In the establishment of the pathogenic process, the cell wall of C. albicans (as in other pathogenic fungi) plays an important role. It is the outer structure that protects the fungus from the host defense mechanisms and initiates the direct contact with the host cells by adhering to their surface. The wall also contains important antigens and other compounds that affect the homeostatic equilibrium of the host in favor of the parasite. In this review, we discuss our present knowledge of the structure of the cell wall of C. albicans, the synthesis of its different components, and the mechanisms involved in their organization to give rise to a coherent composite. Furthermore, special emphasis has been placed on two further aspects: how the composition and structure of C. albicans cell wall compare with those from other fungi, and establishing the role of some specific wall components in pathogenesis. From the data presented here, it becomes clear that the composition, structure and synthesis of the cell wall of C. albicans display both subtle and important differences with the wall of different saprophytic fungi, and that some of these differences are of utmost importance for its pathogenic behavior.

Plant-microbe interactions are ubiquitous. Plants are threatened by pathogens, but they are even more commonly engaged in neutral or mutualistic interactions with microbes: belowground microbial plant associates are mycorrhizal fungi, Rhizobia, and plant-growth promoting rhizosphere bacteria, aboveground plant parts are colonized by internally living bacteria and fungi (endophytes) and by microbes in the phyllosphere (epiphytes). We emphasize here that a completely microbe-free plant is an exotic exception rather than the biologically relevant rule. The complex interplay of such microbial communities with the host-plant affects multiple vital parameters such as plant nutrition, growth rate, resistance to biotic and abiotic stressors, and plant survival and distribution. The mechanisms involved reach from direct ones such as nutrient acquisition, the production of plant hormones, or direct antibiosis, to indirect ones that are mediated by effects on host resistance genes or via interactions at higher trophic levels. Plant-associated microbes are heterotrophic and cause costs to their host plant, whereas the benefits depend on the current environment. Thus, the outcome of the interaction for the plant host is highly context dependent. We argue that considering the microbe-free plant as the "normal" or control stage significantly impairs research into important phenomena such as (1) phenotypic and epigenetic plasticity, (2) the "normal" ecological outcome of a given interaction, and (3) the evolution of plants. For the future, we suggest cultivation-independent screening methods using direct PCR from plant tissue of more than one fungal and bacterial gene to collect data on the true microbial diversity in wild plants. The patterns found could be correlated to host species and environmental conditions, in order to formulate testable hypotheses on the biological roles of plant endophytes in nature. Experimental approaches should compare different host-endophyte combinations under various relevant environmental conditions and study at the genetic, epigenetic, transcriptional, and physiological level the parameters that cause the interaction to shift along the mutualism-parasitism continuum.

Estimation of genetic diversity and distance among tropical maize ( Zea mays L.) lines and the correlation between genetic distance (GD) and hybrid performance would determine breeding strategies, classify inbred lines, define heterotic groups, and predict future hybrid performance. The objectives of this study were to estimate (i) heterosis and specific combining ability (SCA) for grain yield under stress and non‐stress environments; (ii) genetic diversity for restriction fragment length polymorphisms (RFLPs) within a set of tropical lines; (iii) GD and classify the lines according to their GD; and (iv) correlation between the GD and hybrid performance, heterosis, and SCA. Seventeen lowland, white tropical inbred lines were represented in a diallel study. Inbred lines and hybrids were evaluated in 12 stress and nonstress environments. The expression of heterosis was greater under drought stress and smaller under low N environments than under nonstress environments. A set of DNA markers identifying 81 loci was used to fingerprint the 17 lines. The level of genetic diversity was high, with 4.65 alleles/locus and polymorphism information content (PIC) values ranging from 0.11 to 0.82. Genomic regions with quantitative trait loci (QTL) for drought tolerance previously identified showed lower genetic diversity. Genetic distance based on RFLP marker data classified the inbred lines in accordance with their pedigree. Positive correlation was found between GD and F 1 performance (F 1 ), SCA, midparent heterosis (MPH) and high‐parent heterosis (HPH). Specific combining ability had the strongest correlation with GD. Environment significantly affected the correlations between F 1 , SCA, MPH, and HPH, with lower values of GD revealed in the more stressed conditions.

Glucans are the most abundant polysaccharides in the cell walls of fungi, and their structures are highly variable. Accordingly, their glucose moieties may be joined through either or both alpha (α) or beta (β) linkages, they are either lineal or branched, and amorphous or microfibrillar. Alpha 1,3 glucans sensu strictu (pseudonigerans) are the most abundant alpha glucans present in the cell walls of fungi, being restricted to dikarya. They exist in the form of structural microfibrils that provide resistance to the cell wall. The structure of beta glucans is more complex. They are linear or branched, and contain mostly β 1,3 and β 1,6 linkages, existing in the form of microfibrils. Together with chitin they constitute the most important structural components of fungal cell walls. They are the most abundant components of the cell walls in members of all fungal phyla, with the exception of Microsporidia, where they are absent. Taking into consideration the importance of glucans in the structure and physiology of the fungi, in the present review we describe the following aspects of these polysaccharides: i) types and distribution of fungal glucans, ii) their structure, iii) their roles, iv) the mechanism of synthesis of the most important ones, and v) the phylogentic relationships of the enzymes involved in their synthesis.

Plants secrete extrafloral nectar (EFN) as an induced defense against herbivores. EFN contains not only carbohydrates and amino acids but also pathogenesis-related proteins and other protective enzymes, making EFN an exclusive reward. EFN secretion is commonly induced after wounding, likely owing to a jasmonic acid-induced cell wall invertase, and is limited by phloem sucrose availability: Both factors control EFN secretion according to the optimal defense hypothesis. Non-ant EFN consumers include parasitoids, wasps, spiders, mites, bugs, and predatory beetles. Little is known about the relevance of EFN to the nutrition of its consumers and, hence, to the structuring of arthropod communities. The mutualism can be established quickly among noncoevolved (e.g., invasive) species, indicating its easy assembly is due to ecological fitting. Therefore, increasing efforts are directed toward using EFN in biocontrol. However, documentation of the importance of EFN for the communities of plants and arthropods in natural, invasive, and agricultural ecosystems is still limited.

BACKGROUND: Drought is one of the major constraints for plant productivity worldwide. Different mechanisms of drought-tolerance have been reported for several plant species including maize. However, the differences in global gene expression between drought-tolerant and susceptible genotypes and their relationship to physiological adaptations to drought are largely unknown. The study of the differences in global gene expression between tolerant and susceptible genotypes could provide important information to design more efficient breeding programs to produce maize varieties better adapted to water limiting conditions. METHODOLOGY/PRINCIPAL FINDINGS: Changes in physiological responses and gene expression patterns were studied under drought stress and recovery in three Mexican maize landraces which included two drought tolerant (Cajete criollo and Michoacán 21) and one susceptible (85-2) genotypes. Photosynthesis, stomatal conductance, soil and leaf water potentials were monitored throughout the experiment and microarray analysis was carried out on transcripts obtained at 10 and 17 days following application of stress and after recovery irrigation. The two tolerant genotypes show more drastic changes in global gene expression which correlate with different physiological mechanisms of adaptation to drought. Differences in the kinetics and number of up- and down-regulated genes were observed between the tolerant and susceptible maize genotypes, as well as differences between the two tolerant genotypes. Interestingly, the most dramatic differences between the tolerant and susceptible genotypes were observed during recovery irrigation, suggesting that the tolerant genotypes activate mechanisms that allow more efficient recovery after a severe drought. CONCLUSIONS/SIGNIFICANCE: A correlation between levels of photosynthesis and transcription under stress was observed and differences in the number, type and expression levels of transcription factor families were also identified under drought and recovery between the three maize landraces. Gene expression analysis suggests that the drought tolerant landraces have a greater capacity to rapidly modulate more genes under drought and recovery in comparison to the susceptible landrace. Modulation of a greater number of differentially expressed genes of different TF gene families is an important characteristic of the tolerant genotypes. Finally, important differences were also noted between the tolerant landraces that underlie different mechanisms of achieving tolerance.

Chia ( Salvia hispanica L.) is a plant that produces seeds rich in some nutraceutical compounds with high protein content, but little is known about them; for this reason the aim of this study was to characterize the seed storage proteins. Protein fractions were extracted from chia seed flour. The main protein fraction corresponded to globulins (52%). Sedimentation coefficient studies showed that the globulin fraction contains mostly 11S and 7S proteins. The molecular sizes of all the reduced fractions were about 15-50 kDa. Electrophoretic experiments under native conditions exhibited four bands of globulins in the range of 104-628 kDa. The denaturation temperatures of crude albumins, globulins, prolamins, and glutelins were 103, 105, 85.6, and 91 °C, respectively; albumins and globulins had relatively good thermal stability. Selected globulin peptides by mass spectrometry showed homology to sesame proteins. A good balance of essential amino acids was found in the seed flour and globulins, especially of methionine+cysteine.

This review provides current information on starch and its molecular composition, common and potential sources, and manufacturing processes. It also deals with the five groups of enzymes involved in the hydrolysis of starch: the endo- and exoamylases, which act primarily on the alpha-1,4 linkages; the debranching enzymes, which act on the alpha-1,6 linkages; the isomerases which convert glucose to fructose; and the cyclodextrin glycosyltransferases which degrade starch by catalyzing cyclization and disproportionation reactions. This work mainly discusses the enzymatic processes for the manufacture of maltodextrins and corn syrup solids, including the production, both batch and continuous, of glucose syrup, and the processes to obtain sweeteners, such as maltose and 42, 55, and 90% high-fructose corn syrups. It highlights the novel production of Schardinger's dextrins: the alpha-, beta-, and gamma-cyclodextrins, consisting of six, seven, and eight glucose monomers, respectively. New products are emerging on the market that can serve as fat and oil substitutes, moisture-retention compounds, crystal-formation controllers, stabilizers for volatile materials like flavors and spices, or products for the pharmaceutical industry. As a result, particular attention is given to functional properties and applications of the above-cited compounds.

A gene (ech-42; previously named ThEn-42) coding for one of the endochitinases produced by the biocontrol agent Trichoderma harzianum IMI206040 was cloned and characterized. Expression of the cDNA clone in Escherichia coli resulted in bacteria with chitinase activity. This chitinase has been shown to have lytic activity on Botrytis cinerea cell walls in vitro. The ech-42 gene was assigned to a double chromosomal band (chromosome V or VI) upon electrophoretic separation and Southern analysis of the chromosomes. Primer extension analysis indicated that transcription of the gene begins preferentially 109 bp upstream of the translation initiation codon. Expression of ech-42 was strongly enhanced during direct interaction of the mycoparasite with a phytopathogenic fungus when confronted in vitro and by growing it in minimal medium containing chitin as sole carbon source. Similarly, light-induced sporulation resulted in high levels of transcript, suggesting developmental regulation of the gene. The implications of these findings are discussed.

Capsicum species produce fruits that synthesize and accumulate carotenoid pigments, which are responsible for the fruits' yellow, orange and red colors. Chili peppers have been used as an experimental model for studying the biochemical and molecular aspects of carotenoid biosynthesis. Most reports refer to the characterization of carotenoids and content determination in chili pepper fruits from different species, cultivars, varieties or genotypes. The types and levels of carotenoids differ between different chili pepper fruits, and they are also influenced by environmental conditions. Yellow-orange colors of chili pepper fruits are mainly due to the accumulation of α- and β-carotene, zeaxanthin, lutein and β-cryptoxanthin. Carotenoids such as capsanthin, capsorubin and capsanthin-5,6-epoxide confer the red colors. Chromoplasts are the sites of carotenoid pigment synthesis and storage. According to the most accepted theory, the synthesis of carotenoids in chili peppers is controlled by three loci: c1, c2 and y. Several enzymes participating in carotenoid biosynthesis in chili pepper fruits have been isolated and characterized, and the corresponding gene sequences have been reported. However, there is currently limited information on the molecular mechanisms that regulate this biosynthetic pathway. Approaches to gain more knowledge of the regulation of carotenoid biosynthesis are discussed.

Herbivore-induced plant volatiles affect the systemic response of plants to local damage and hence represent potential plant hormones. These signals can also lead to "plant-plant communication," a defense induction in yet undamaged plants growing close to damaged neighbors. We observed this phenomenon in the context of disease resistance. Lima bean (Phaseolus lunatus) plants in a natural population became more resistant against a bacterial pathogen, Pseudomonas syringae pv syringae, when located close to conspecific neighbors in which systemic acquired resistance to pathogens had been chemically induced with benzothiadiazole (BTH). Airborne disease resistance induction could also be triggered biologically by infection with avirulent P. syringae. Challenge inoculation after exposure to induced and noninduced plants revealed that the air coming from induced plants mainly primed resistance, since expression of PATHOGENESIS-RELATED PROTEIN2 (PR-2) was significantly stronger in exposed than in nonexposed individuals when the plants were subsequently challenged by P. syringae. Among others, the plant-derived volatile nonanal was present in the headspace of BTH-treated plants and significantly enhanced PR-2 expression in the exposed plants, resulting in reduced symptom appearance. Negative effects on growth of BTH-treated plants, which usually occur as a consequence of the high costs of direct resistance induction, were not observed in volatile organic compound-exposed plants. Volatile-mediated priming appears to be a highly attractive means for the tailoring of systemic acquired resistance against plant pathogens.

Specialized or secondary metabolites are small molecules of biological origin, often showing potent biological activities with applications in agriculture, engineering and medicine. Usually, the biosynthesis of these natural products is governed by sets of co-regulated and physically clustered genes known as biosynthetic gene clusters (BGCs). To share information about BGCs in a standardized and machine-readable way, the Minimum Information about a Biosynthetic Gene cluster (MIBiG) data standard and repository was initiated in 2015. Since its conception, MIBiG has been regularly updated to expand data coverage and remain up to date with innovations in natural product research. Here, we describe MIBiG version 4.0, an extensive update to the data repository and the underlying data standard. In a massive community annotation effort, 267 contributors performed 8304 edits, creating 557 new entries and modifying 590 existing entries, resulting in a new total of 3059 curated entries in MIBiG. Particular attention was paid to ensuring high data quality, with automated data validation using a newly developed custom submission portal prototype, paired with a novel peer-reviewing model. MIBiG 4.0 also takes steps towards a rolling release model and a broader involvement of the scientific community. MIBiG 4.0 is accessible online at https://mibig.secondarymetabolites.org/.