217 research outputs found
Lobe-generating centres in the simple leaves of Myriophyllum aquaticum: evidence for KN1-like activity
No full textBackground and Aims
The mature morphology of most plants can usually be said to consist of three mutually exclusive organs: leaves, stems, and roots. The vast majority of mature morphologies may be easily grouped into one of these mutually exclusive categories. However, during very early stages of development and in many instances from inception, the division between organ categories becomes fuzzy due to the overlap in developmental processes that are shared between the aforementioned mutually exclusive categories. One such overlap has been described at the gene level where KNOXI homologues, transcription factors responsible for maintaining indeterminate cell fate, are expressed in the shoot apical meristem and during early stages of compound leaf development. This study characterizes the occurrence and spatial localization of mRNA of a KNOXI homologue, MaKN1, during the early stages of development in the simple leaves of Myriophyllum aquaticum, an aquatic angiosperm from the family Haloragaceae exhibiting pentamerous whorls of finely lobed leaves.
Methods
A 300-bp KNOXI fragment was sequenced from M. aquaticum and used in an RNA localization study to determine the temporal and spatial expression of KNOXI during the early stages of leaf lobe development in M. aquaticum. The developmental sequence of leaves of M. aquaticum was also described using scanning electron microscopy.
Key Results
Lobe development of M. aquaticum occurs in two very distinct regions at the leaf base in an alternating fashion reminiscent of a distichous shoot system. It was discovered that MaKN1 expression is localized to both the shoot apical meristem and early stages of leaf primordia development (P1–P7). Initially, MaKN1 is expressed ubiquitously throughout primordia (P1–P3); however, as lobes develop, MaKN1 becomes localized to recently emerged lobe primordia, and disappears as lobes develop basipetally.
Conclusions
The pattern of gene expression is indicative of shared developmental processes during early development between shoots, compound leaves, highly lobed simple leaves and unifoliate simple leaves which lack KNOXI expression. These findings are supportive of Arber's less rigid ‘partial shoot’ theory, which conceptualizes compound leaves as having shoot-like elements
Phyllotaxis of the palm Euterpe oleracea Mart. at the level of the shoot apical meristem
No full textPrevious studies on palm phyllotaxis deal mainly with the mature trunk. The goals of this study are (i) to determine the relationship between the number of parastichies, the divergence angle, and the plastochrone ratio at the level of the shoot apical meristem; (ii) to examine whether there are fluctuations in the divergence angle; (iii) to interpret the significance of phyllotactic parameters with respect to the mode of growth of the apex. The tubular base of the leaf primordium is more or less asymmetrical, and completely surrounds the shoot apical meristem. The phyllotactic system corresponds to a (2, 3) conspicuous parastichy pair. The mean divergence angle per apex varies between 126.9 degrees +/- 9.3 degrees (mean +/- SD) and 135.degrees +/- 8.0 degrees. Divergence angles for all apices fluctuate within a range of 115.89 degrees to 157.33 degrees. The mean plastochrone ratios between apices varies from 1.35 degrees +/- 0.18 degrees to 1.58 +/- 0.12. The plastochrone ratio at each plastochrone for all apices ranges from 1.09 to 2.00. There is no correlation between the angle of divergence and the plastochrone ratio. There is a fluctuation in the value of the divergence angle that falls within the range predicted by the fundamental theorem of phyllotaxis. The high value of the ratio of the diameter of leaf primordia over the diameter of the apex, and the long plastochrone might explain the lack of correlation between certain phyllotactic parameters.PT: J; UT: BIOSIS:PREV201000395117Source type: Electronic(1
First report of Myxobolus neurofontinalis (Bivalvulida: Myxobolidae) infecting anadromous Brook Trout from Prince Edward Island, Canada
No full textObjective
During routine histological examination of tissues from mortality events of anadromous Brook Trout Salvelinus fontinalis from Prince Edward Island (PEI), Canada, myxospores consistent with Myxobolus were observed infecting the central nervous system. The objective of this study was to identify the species of Myxobolus infecting the nervous system of anadromous Brook Trout from PEI, Canada.
Methods
Myxospore morphology, small subunit (SSU) ribosomal DNA (rDNA) sequence data, and histology were used to identify myxospores isolated from infected Brook Trout.
Result
Myxospore measurements from the PEI samples matched those reported in the description of Myxobolus neurofontinalis from North Carolina. A 1057-bp fragment of the SSU rDNA from myxospores collected from Brook Trout in PEI was identical to an isolate of M. neurofontinalis (MN191598) collected previously from the type locality, New River basin, North Carolina. Histological sections confirmed infections were intercellular in the central nervous system. Minimal host response was observed, with only sparse mononuclear inflammatory infiltrates present at the periphery of and within dispersed myxospores, suggesting that infections are not pathogenic to Brook Trout.
Conclusion
Myxospores were identified as M. neurofontinalis, which was previously described from the central nervous system of Brook Trout from the New River basin, North Carolina, USA. This constitutes the first time M. neurofontinalis has been documented outside of the New River basin in North Carolina
Guillaume Colletet. Cyminde or the Two Victims (1642): The poet's only single-author play. Edited and commented by Bernard J. Bourque
No full textComposée à l'instigation de Richelieu, Cyminde ou les deux victimes (1642) est la seule pièce de théâtre à auteur unique de Guillaume Colletet, l'un des premiers membres de l'Académie française et l'un des « cinq auteurs » choisis par le cardinal pour collaborer à la composition d'ouvrages dramatiques. Bien que l'œuvre soit l'adaptation en vers d'une pièce en prose de l'abbé d'Aubignac, elle subit une transformation sous la plume de Colletet, le poète se donnant carte blanche pour la création du dialogue. Le travail est la première édition critique de la pièce. Ce livre a pour but de rendre cette œuvre plus facilement accessible et d'offrir des explications et des commentaires afin de faciliter sa lecture. L'édition permettra une meilleure connaissance de Colletet, connu surtout pour ses poésies, dans sa brève carrière de dramaturge. L'édition comporte une introduction et près de 300 notes. Une analyse critique, en des Observations, tente à rendre à cette pièce sa valeur dramatique et historique
Acute toxoplasmosis and pox-viral dermatitis in a juvenile bald eagle (Haliaeetus leucocephalus) in New Brunswick, Canada.
No full textAlthough birds of prey are commonly subclinically infected by Toxoplasma gondii tissue cysts, clinical disease is relatively rare in these species. The present report describes a rare case of fatal toxoplasmosis in a juvenile bald eagle in New Brunswick. Necropsy investigation revealed severe emaciation and poxviral dermatitis which partially obscured the palpebral fissures. Microscopically there was severe lymphoplasmacytic inflammation and necrosis of the lung that was associated with abundant protozoal tachyzoites. Infection with T. gondii was confirmed in the lung via immunohistochemistry and DNA sequencing.
Key clinical message:
Wildlife rehabilitation centers should be aware of the potential occurrence of acute clinical toxoplasmosis in stressed malnourished raptors.case reports2020 08importe
Identification of avian bornavirus in a Himalayan monal (Lophophorus impejanus) with neurological disease
No full textA one-year-old male Himalayan monal (Lophophorus impejanus) was presented for veterinary attention with a history of chronic wasting, weakness and ataxia. The bird died, and post-mortem findings included mild non-suppurative encephalitis and degenerative encephalopathy, lymphoplasmacytic myenteric ganglioneuritis (particularly of the proventriculus), and Wallerian degeneration of the sciatic nerves. Avian bornavirus (ABV) was identified in the brain by immunohistochemistry and reverse-transcriptase polymerase chain reaction. Sequencing of the reverse-transcriptase polymerase chain reaction product indicated the presence of ABV genotype 4, which is generally associated with disease in psittacine birds. Subsequent to the death of the pheasant, ABV genotype 4 was identified at autopsy from a juvenile white-bellied caique (Pionites leucogaster) in the same collection. We hypothesize that the pheasant became infected through contact with psittacine birds with which it shared an aviary. We believe this to be the first reported case of natural ABV infection in a bird in the Order Galliformes
Evidence for partial homology: Examining the morphological and molecular relationships between shoot and leaf development in watermilfoil (Myriophyllum aquaticum)
No full textThere is evidence from both morphological and molecular studies that many shoots and leaves have analogous developmental characteristics which transcend their classical categorization. An example of this can be found in the expression patterns of the KNOX1 family of homeobox genes which function in maintenance of indeterminate growth and are expressed in both dissected leaves and shoots. Shoot and leaf morphological parallels were characterized in the aquatic angiosperm Myriophyllum aquaticum (Vel.) using a combination of scanning electron microscopy and standard light microscopy. A KNOX1 gene fragment was also sequenced from M. aquaticum and its pattern of expression was mapped at the shoot tip using RNA in situ hybridization as the primary technique. Leaves were found to develop lobes in an alternating basipetal fashion and originated from distinct generative centers at the leaf base. Within the tissues of the developing shoot, KNOX1 expression was found to be localized to the developing stem, provascular strands, dermal tissues of internodes, and between developing leaf bases. KNOX1 expression was also found within developing leaves where patterns varied depending on the age of the primordium. In leaves between plastochrones 1 and 3, KNOX1 is evenly expressed throughout the primordium. In older plastochrones, expression becomes localized the more recently developed lobes. By plastochrone 9, expression signal is no longer visible. The presence of distinct lobe forming centers at the base of the leaf and the corresponding KNOX1 expression during leaf and shoot development is indicative of developmental parallels between traditionally non homologous structures.Source: Masters Abstracts International, Volume: 47-06, page: 3440
Benzo(a)pyrene suppresses tracheal antimicrobial peptide gene expression in bovine tracheal epithelial cells
No full text
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