Time filter

Source Type

McLaughlin D.J.,University of Minnesota | Healy R.A.,University of Minnesota | Healy R.A.,Harvard University | Celio G.J.,University of Minnesota | And 2 more authors.
American Journal of Botany | Year: 2015

Premise of the study: The earliest eukaryotes were likely fl agellates with a centriole that nucleates the centrosome, the microtubule-organizing center (MTOC) for nuclear division. The MTOC in higher fungi, which lack fl agella, is the spindle pole body (SPB). Can we detect stages in centrosome evolution leading to the diversity of SPB forms observed in terrestrial fungi? Zygomycetous fungi, which consist of saprobes, symbionts, and parasites of animals and plants, are critical in answering the question, but nuclear division has been studied in only two of six clades. • Methods: Ultrastructure of mitosis was studied in Coemansia revers a (Kickxellomycotina) germlings using cryofi xation or chemical fi xation. Character evolution was assessed by parsimony analysis, using a phylogenetic tree assembled from multigene analyses. • Key results: At interphase the SPB consisted of two components: a cytoplasmic, electron-dense sphere containing a cylindrical structure with microtubules oriented nearly perpendicular to the nucleus and an intranuclear component appressed to the nuclear envelope. Markham’s rotation was used to reinforce the image of the cylindrical structure and determine the probable number of microtubules as nine. The SPB duplicated early in mitosis and separated on the intact nuclear envelope. Nuclear division appears to be intranuclear with spindle and kinetochore microtubules interspersed with condensed chromatin. • Conclusions: This is the sixth type of zygomycetous SPB, and the third type that suggests a modifi ed centriolar component. Coemansia reversa retains SPB character states from an ancestral centriole intermediate between those of fungi with motile cells and other zygomycetous fungi and Dikarya. © 2015 Botanical Society of America Source

Bentivenga S.P.,University of Wisconsin - Oshkosh | Arun Kumar T.K.,The Zamorins Guruvayurappan College | Kumar L.,University of Minnesota | Roberson R.W.,Arizona State University | McLaughlin D.J.,University of Minnesota
Mycologia | Year: 2013

Comparative morphology of the fine structure of fungal hyphal tips often is phylogenetically informative. In particular, morphology of the Spitzenko ̈rper varies among higher taxa. To date no one has thoroughly characterized the hyphal tips of members of the phylum Glomeromycota to compare them with other fungi. This is partly due to difficulty growing and manipulating living hyphae of these obligate symbionts. We observed growing germ tubes of Gigaspora gigantea, G. margarita and G. rosea with a combination of light microscopy (LM) and transmission electron microscopy (TEM). For TEM, we used both traditional chemical fixation and cryo-fixation methods. Germ tubes of all species were extremely sensitive to manipulation. Healthy germ tubes often showed rapid bidirectional cytoplasmic streaming, whereas germ tubes that had been disturbed showed reduced or no cytoplasmic movement. Actively growing germ tubes contain a cluster of 10-20 spherical bodies approximately 3-8 mm behind the apex. The bodies, which we hypothesize are lipid bodies, move rapidly in healthy germ tubes. These bodies disappear immediately after any cellular perturbation. Cells prepared with cryo-techniques had superior preservation compared to those that had been processed with traditional chemical protocols. For example, cryo-prepared samples displayed two cell-wall layers, at least three vesicle types near the tip and three distinct cytoplasmic zones were noted. We did not detect a Spitzenkörper with either LM or TEM techniques and the tip organization of Gigaspora germ tubes appeared to be similar to hyphae in zygomycetous fungi. This observation was supported by a phylogenetic analysis of microscopic characters of hyphal tips from members of five fungal phyla. Our work emphasizes the sensitive nature of cellular organization, and the need for as little manipulation as possible to observe germ tube structure accurately. © 2013 by The Mycological Society of America. Source

Pradeep C.K.,Jawaharlal Nehru Tropical Botanic Garden and Research Institute | Vrinda K.B.,Jawaharlal Nehru Tropical Botanic Garden and Research Institute | Varghese S.P.,Jawaharlal Nehru Tropical Botanic Garden and Research Institute | Arun Kumar T.K.,The Zamorins Guruvayurappan College
Phytotaxa | Year: 2015

A new species of Phylloporus from Kerala State, India is described, illustrated and discussed based on morphological and molecular characters. The phylogenetic relationship with related species based on ITS sequences is also provided. © 2015 Magnolia Press. Source

Discover hidden collaborations