RESUMEN
We have analyzed the expression pattern of protocadherin-19, a member of the delta2-protocadherins, in the nervous system of developing zebrafish using in situ hybridization methods. mRNA encoding protocadherin-19 (Pcdh19) began to be expressed at about 12 hours post fertilization (hpf) showing a segmental expression pattern in the anterior 1/3 of the neural keel, with strong expression in the presumptive forebrain, cerebellum/rhombomere 1 and rhombomere 4. Pcdh19 expression in the posterior neural keel was continuous and confined to the midline region. By 24 hpf, Pcdh19 was expressed widely in the brain and spinal cord, with higher expression levels in the ventral telencephalon, dorsal and central thalamus, optic tectum, central tegmentum, cerebellum and dorsolateral regions of the hindbrain. As development proceeded, Pcdh19 expression domains became restricted to the dorsal and/or lateral regions of the central nervous system, and Pcdh19 expression was not detected in the spinal cord of two- and three-day old embryos. Pcdh19 was also expressed by the eye primordium, developing retina, lens and otic vesicle. Similar to its expression in the brain, Pcdh19 expression in the eye and ear was also spatially and temporally regulated.
Asunto(s)
Cadherinas/genética , Sistema Nervioso Central/metabolismo , Perfilación de la Expresión Génica , Regulación del Desarrollo de la Expresión Génica , Proteínas de Pez Cebra/genética , Pez Cebra/genética , Secuencia de Aminoácidos , Animales , Encéfalo/embriología , Encéfalo/metabolismo , Cadherinas/clasificación , Cadherinas/metabolismo , Sistema Nervioso Central/embriología , Oído Externo/embriología , Oído Externo/metabolismo , Oído Interno/embriología , Oído Interno/metabolismo , Oído Medio/embriología , Oído Medio/metabolismo , Embrión no Mamífero/embriología , Embrión no Mamífero/metabolismo , Ojo/embriología , Ojo/metabolismo , Inmunohistoquímica , Hibridación in Situ , Datos de Secuencia Molecular , Filogenia , Protocadherinas , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Homología de Secuencia de Aminoácido , Factores de Tiempo , Pez Cebra/embriología , Proteínas de Pez Cebra/clasificación , Proteínas de Pez Cebra/metabolismoRESUMEN
Endophytic fungi represent diverse taxa that inhabit plant hosts without causing disease symptoms. We used endophytic isolates of Fusarium verticillioides (Sacc.) Nirenberg to understand how endophytic fungi interact with pathogens, in this case, the corn smut pathogen, Ustilago maydis DC (Corda). Endophytic F. verticillioides strains were inoculated onto maize seedlings before, simultaneously, or after inoculation with U. maydis, and the effects on smut disease severity and on plant growth were assessed. When F. verticillioides is simultaneously coinoculated with U. maydis, smut disease severity is significantly decreased and plant growth is increased, compared with other treatments. Controls show that F. verticillioides by itself does not have measurable effects on plant growth. Together, our results suggest that a commonly occurring fungal endophyte on maize, F. verticillioides, ameliorates the effects of a host-specific pathogen, U. maydis, by interfering with the early infection process and limiting disease development, resulting in increased plant growth.
Asunto(s)
Fusarium/fisiología , Enfermedades de las Plantas/microbiología , Simbiosis , Ustilago/fisiología , Zea mays/microbiología , Zea mays/crecimiento & desarrolloRESUMEN
In this study we analyzed expression patterns of two delta-protocadherins, protocadherin-9 and protocadherin-17, in the developing zebrafish using in situ hybridization and RT-PCR methods. Both protocadherins were mainly detected in the embryonic central nervous system, but each showed a distinct expression pattern. Protocadherin-9 message (Pcdh9) was expressed after 10h post fertilization (hpf). It was found mainly in small clusters of cells in the anteroventral forebrain and ventrolateral hindbrain, and scattered cells throughout the spinal cord of young embryos (24 hpf). Pcdh9 expression in the hindbrain was segmental, reflecting a neuromeric organization, which became more evident at 34 hpf. As development proceeded, Pcdh9 expression increased throughout the brain, while its expression in the spinal cord was greatly reduced. Pcdh9 was also found in the developing retina and statoacoustic ganglion. Protocadherin-17 message (Pcdh17) expression began much earlier (1.5-2 hpf) than Pcdh9. Similar to Pcdh9 expression, Pcdh17 expression was found mainly in the anteroventral forebrain at 24 hpf, but its expression in the hindbrain and spinal cord, confined mainly to lateroventral regions of the hindbrain and anterior spinal cord, was more restricted than Pcdh9. As development proceeded, Pcdh17 expression was increased both in the brain and spinal cord: detected throughout the brain of two- and three-day old embryos, strongly expressed in the retina and in lateral regions of spinal cord in two-day old embryos. Its expression in the retina and spinal cord was reduced in three-day old embryos. Our results showed that expression of these two protocadherins was both spatially and temporally regulated.
Asunto(s)
Cadherinas/genética , Sistema Nervioso Central/embriología , Embrión no Mamífero/metabolismo , Regulación del Desarrollo de la Expresión Génica , Proteínas de Pez Cebra/genética , Pez Cebra/embriología , Secuencia de Aminoácidos , Animales , Encéfalo/embriología , Cadherinas/metabolismo , Sistema Nervioso Central/metabolismo , Clonación Molecular , Hibridación in Situ , Datos de Secuencia Molecular , Protocadherinas , Retina/embriología , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Alineación de Secuencia , Médula Espinal/embriología , Proteínas de Pez Cebra/metabolismoRESUMEN
Many factors can affect the assembly of communities, ranging from species pools to habitat effects to interspecific interactions. In microbial communities, the predominant focus has been on the well-touted ability of microbes to disperse and the environment acting as a selective filter to determine which species are present. In this study, we investigated the role of biotic interactions (e.g., competition, facilitation) in fungal endophyte community assembly by examining endophyte species co-occurrences within communities using null models. We used recombinant inbred lines (genotypes) of maize (Zea mays) to examine community assembly at multiple habitat levels, at the individual plant and host genotype levels. Both culture-dependent and culture-independent approaches were used to assess endophyte communities. Communities were analyzed using the complete fungal operational taxonomic unit (OTU) dataset or only the dominant (most abundant) OTUs in order to ascertain whether species co-occurrences were different for dominant members compared to when all members were included. In the culture-dependent approach, we found that for both datasets, OTUs co-occurred on maize genotypes more frequently than expected under the null model of random species co-occurrences. In the culture-independent approach, we found that OTUs negatively co-occurred at the individual plant level but were not significantly different from random at the genotype level for either the dominant or complete datasets. Our results showed that interspecific interactions can affect endophyte community assembly, but the effects can be complex and depend on host habitat level. To our knowledge, this is the first study to examine endophyte community assembly in the same host species at multiple habitat levels. Understanding the processes and mechanisms that shape microbial communities will provide important insights into microbial community structure and the maintenance of microbial biodiversity.
Asunto(s)
Ecosistema , Hongos/aislamiento & purificación , Zea mays/microbiología , ADN de Hongos/genética , ADN Espaciador Ribosómico/genética , Hongos/genética , Genotipo , Dinámica Poblacional , Análisis de Secuencia de ADN , Especificidad de la Especie , Zea mays/genéticaRESUMEN
The focus of many fungal endophyte studies has been how plants benefit from endophyte infection. Few studies have investigated the role of the host plant as an environment in shaping endophyte community diversity and composition. The effects that different attributes of the host plant, that is, host genetic variation, host variation in resistance to the fungal pathogen Ustilago maydis and U. maydis infection, have on the fungal endophyte communities in maize (Zea mays) was examined. The internal transcribed spacer (ITS) region of the rDNA was sequenced to identify fungi and the endophyte communities were compared in six maize lines that varied in their resistance to U. maydis. It was found that host genetic variation, as determined by maize line, had significant effects on species richness, while the interactions between line and U. maydis infection and line and field plot had significant effects on endophyte community composition. However, the effects of maize line were not dependent on whether lines were resistant or susceptible to U. maydis. Almost 3000 clones obtained from 58 plants were sequenced to characterize the maize endophyte community. These results suggest that the endophyte community is shaped by complex interactions and factors, such as inoculum pool and microclimate, may be important.
Asunto(s)
Ecosistema , Simbiosis/fisiología , Ustilago/fisiología , Zea mays/microbiología , Plantas Modificadas Genéticamente/inmunología , Plantas Modificadas Genéticamente/microbiología , Reacción en Cadena de la Polimerasa , Zea mays/genética , Zea mays/inmunologíaRESUMEN
Parasites and pathogens are hypothesized to change host growth, reproduction and/or behaviour to increase their own transmission. However, studies which clearly demonstrate that parasites or pathogens are directly responsible for changes in hosts are lacking. We previously found that infection by the systemic fungus Epichloë glyceriae was associated with greater clonal growth by its host, Glyceria striata. Whether greater clonal growth resulted directly from pathogen infection or indirectly from increased likelihood of infection for host genotypes with greater clonal growth could not be determined because only naturally infected and uninfected plants were used. In this study, we decoupled infection and host genotype to evaluate the role of pathogen infection on host development and clonal growth. We found that total biomass production did not differ for clones of the same genotype, but infected clones allocated more biomass to clonal growth. Disinfected clones had more tillers and a greater proportion of their biomass in the mother ramet. Infected clones produced fewer tillers but significantly more and longer stolons than disinfected clones. These results support the hypothesis that pathogen infection directly alters host development. Parasite alteration of clonal growth patterns might be advantageous to the persistence and spread of host plants in some ecological conditions.