RESUMEN
BACKGROUND: The distribution of the wild turkey (Meleagris gallopavo) extends from Mexico to southeastern Canada and to the eastern and southern regions of the USA. Six subspecies have been described based on morphological characteristics and/or geographical variations in wild and domesticated populations. In this paper, based on DNA sequence data from the mitochondrial D-loop, we investigated the genetic diversity and structure, genealogical relationships, divergence time and demographic history of M. gallopavo populations including domesticated individuals. RESULTS: Analyses of 612 wild and domesticated turkey mitochondrial D-loop sequences, including 187 that were collected for this study and 425 from databases, revealed 64 haplotypes with few mutations, some of which are shared between domesticated and wild turkeys. We found a high level of haplotype and nucleotide diversity, which suggests that the total population of this species is large and stable with an old evolutionary history. The results of genetic differentiation, haplotype network, and genealogical relationships analyses revealed three main genetic groups within the species: mexicana as a population relict (C1), merriami (C2), and mexicana/intermedia/silvestris/osceola (C3). Haplotypes detected in domesticated turkeys belong to group C3. Estimates of divergence times agree with range expansion and diversification events of the relict population of M. gallopavo in northwestern Mexico during the Pliocene-Pleistocene and Pleistocene-Holocene boundaries. Demographic reconstruction showed that an expansion of the population occurred 110,000 to 130,000 years ago (Kya), followed by a stable period 100 Kya and finally a decline ~ 10 Kya (Pleistocene-Holocene boundary). In Mexico, the Trans-Mexican Volcanic Belt may be responsible for the range expansion of the C3 group. Two haplotypes with different divergence times, MGMDgoB/MICH1 and MICH2, are dominant in domesticated and commercial turkeys. CONCLUSIONS: During the Pleistocene, a large and stable population of M. gallopavo covered a wide geographic distribution from the north to the center of America (USA and Mexico). The mexicana, merriami, and mexicana/intermedia/silvestris/osceola genetic groups originated after divergence and range expansion from northwestern Mexico during the Pliocene-Pleistocene and Pleistocene-Holocene boundaries. Old and new maternal lines of the mexicana/intermedia/silvestris/osceola genetic group were distributed within the Trans-Mexican Volcanic Belt where individuals were captured for domestication. Two haplotypes are the main founder maternal lines of domesticated turkeys.
Asunto(s)
Animales Domésticos/genética , Mitocondrias/genética , Análisis de Secuencia de ADN/veterinaria , Pavos/genética , Animales , Animales Salvajes/genética , Canadá , ADN Mitocondrial/genética , Evolución Molecular , Variación Genética , Guatemala , Haplotipos , México , Filogenia , Pavos/clasificaciónRESUMEN
Pectin lyases (PNLs) are important enzymes that are involved in plant cell wall degradation during the infection process. Colletotrichum is a diverse genus of fungi, which allows the study of the evolution of PNLs and their possible role in pathogen-host interactions and lifestyle adaptations. The phylogenetic reconstruction of PNLs from Colletotrichum and analysis of selection pressures showed the formation of protein lineages by groups of species with different selection pressures and specific patterns. The analysis of positive selection at individual sites using different methods allowed for the identification of three codons with evidence of positive selection in the oligosaccharide-binding region and two codons on the antiparallel sheet, which may influence the interaction with the substrate. Seven codons on the surface of the protein, mainly in the peripheral helices of the PNLs, could have an important function in evasion of plant defenses, as has been proposed in other enzymes. According to our results, it is possible that events of genetic duplication occurred in ancestral lines, followed by episodes of genetic diversification and gene loss, probably influenced by differences in the composition of the host cell wall. Additionally, different patterns of evolution in Colletotrichum appear to be molded by a strong purifying selection and positive selection episodes that forged the observed evolutionary patterns, possibly influenced by host interaction or substrate specificity. This work represents a starting point for the study of sites that may be important for evasion of plant defenses and biotechnological purposes.
Asunto(s)
Colletotrichum/enzimología , Evolución Molecular , Filogenia , Polisacárido Liasas/genética , Colletotrichum/genética , Proteínas Fúngicas/genéticaRESUMEN
The Colletotrichum genus has been considered as one of the top 10 fungal pathogens in molecular plant pathology based on their scientific and agrobiological importance. Although the genus contains species with different lifestyles, most of the Colletotrichum sp. are known by their hemibiotrophic strategy of infection/invasion causing anthracnose disease in many economically important crops. Hemibiotrophy includes two sequential stages of infection, biotrophy and necrotrophy, in a series of steps that involve the participation of different virulence factors. In this review, we present the current status of the knowledge of such factors reported in this genus and a list of related genes identified in Colletotrichum sp. genomes.
Asunto(s)
Colletotrichum/genética , Proteínas Fúngicas/genética , Regulación Fúngica de la Expresión Génica , Genoma Fúngico , Interacciones Huésped-Patógeno , Células Vegetales/microbiología , Factores de Virulencia/genética , Pared Celular/química , Pared Celular/microbiología , Colletotrichum/enzimología , Colletotrichum/patogenicidad , Proteínas Fúngicas/metabolismo , Enfermedades de las Plantas/microbiología , Plantas/microbiología , Transducción de Señal , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Factores de Virulencia/metabolismoRESUMEN
BACKGROUND: Microorganisms produce cell-wall-degrading enzymes as part of their strategies for plant invasion/nutrition. Among these, pectin lyases (PNLs) catalyze the depolymerization of esterified pectin by a ß-elimination mechanism. PNLs are grouped together with pectate lyases (PL) in Family 1 of the polysaccharide lyases, as they share a conserved structure in a parallel ß-helix. The best-characterized fungal pectin lyases are obtained from saprophytic/opportunistic fungi in the genera Aspergillus and Penicillium and from some pathogens such as Colletotrichum gloeosporioides.The organism used in the present study, Colletotrichum lindemuthianum, is a phytopathogenic fungus that can be subdivided into different physiological races with different capacities to infect its host, Phaseolus vulgaris. These include the non-pathogenic and pathogenic strains known as races 0 and 1472, respectively. RESULTS: Here we report the isolation and sequence analysis of the Clpnl2 gene, which encodes the pectin lyase 2 of C. lindemuthianum, and its expression in pathogenic and non-pathogenic races of C. lindemuthianum grown on different carbon sources. In addition, we performed a phylogenetic analysis of the deduced amino acid sequence of Clpnl2 based on reported sequences of PNLs from other sources and compared the three-dimensional structure of Clpnl2, as predicted by homology modeling, with those of other organisms. Both analyses revealed an early separation of bacterial pectin lyases from those found in fungi and oomycetes. Furthermore, two groups could be distinguished among the enzymes from fungi and oomycetes: one comprising enzymes from mostly saprophytic/opportunistic fungi and the other formed mainly by enzymes from pathogenic fungi and oomycetes. Clpnl2 was found in the latter group and was grouped together with the pectin lyase from C. gloeosporioides. CONCLUSIONS: The Clpnl2 gene of C. lindemuthianum shares the characteristic elements of genes coding for pectin lyases. A time-course analysis revealed significant differences between the two fungal races in terms of the expression of Clpnl2 encoding for pectin lyase 2. According to the results, pectin lyases from bacteria and fungi separated early during evolution. Likewise, the enzymes from fungi and oomycetes diverged in accordance with their differing lifestyles. It is possible that the diversity and nature of the assimilatory carbon substrates processed by these organisms played a determinant role in this phenomenon.
Asunto(s)
Colletotrichum/enzimología , Regulación Enzimológica de la Expresión Génica , Regulación Fúngica de la Expresión Génica , Polisacárido Liasas/genética , Clonación Molecular , Colletotrichum/genética , ADN Complementario , Biblioteca de Genes , Datos de Secuencia Molecular , Filogenia , Polisacárido Liasas/química , Polisacárido Liasas/metabolismo , Análisis de Secuencia de ADNRESUMEN
Plant cell wall-degrading enzymes, such as cellulases, hemicellulases and pectinases, have been extensively studied because of their well documented biotechnological potential, mainly in the food industry. In particular, lytic enzymes from filamentous fungi have been the subject of a vast number of studies due both to their advantages as models for enzyme production and their characteristics. The demand for such enzymes is rapidly increasing, as are the efforts to improve their production and to implement their use in several industrial processes, with the goal of making them more efficient and environment-friendly. The present review focuses mainly on pectinolytic enzymes of filamentous fungi, which are responsible for degradation of pectin, one of the major components of the plant cell wall. Also discussed are the past and current strategies for the production of cell wall-degrading enzymes and their present applications in a number of biotechnological areas.