Our findings identify TAC-1 as a core structural and functional member of the evolutionarily conserved TACC family of proteins and suggest that mutual stabilization between TACC and XMAP215 proteins is a key feature ensuring microtubule assembly in vivo.
Proper spindle positioning is essential for spatial control of cell division. Here, we show that zyg-8 plays a key role in spindle positioning during asymmetric division of one-cell stage C. elegans embryos by promoting microtubule assembly during anaphase. ZYG-8 harbors a kinase domain and a domain related to Doublecortin, a microtubule-associated protein (MAP) affected in patients with neuronal migration disorders. Sequencing of zyg-8 mutant alleles demonstrates that both domains are essential for function. ZYG-8 binds to microtubules in vitro, colocalizes with microtubules in vivo, and promotes stabilization of microtubules to drug or cold depolymerization in COS-7 cells. Our findings demonstrate that ZYG-8 is a MAP crucial for proper spindle positioning in C. elegans, and indicate that the function of the Doublecortin domain in modulating microtubule dynamics is conserved across metazoan evolution.
Applying early names, with or without original material, to genealogical species is challenging. For morels this task is especially difficult because of high morphological stasis and high plasticity of apothecium color and shape. Here we propose a nomenclatural revision of true morels (Morchella, Pezizales) from Europe and North America, based on molecular phylogenetic analyses of portions of the genes for RNA polymerase II largest subunit (RPB1) and second largest subunit (RPB2), translation elongation factor-1a (TEF1), the nuc rDNA region encompassing the internal transcribed spacers 1 and 2, along with the 5.8S rDNA (ITS), and partial nuc 28S rDNA D1-D2 domains (28S). The 107 newly sequenced collections were from both continents, including 48 types, together with previously published sequences. Names are applied to 30 of the 65 currently recognized genealogical species. Results of the present study revealed that the number of Morchella species in Europe (n 5 21) is nearly identical to that in North America (n 5 22). Only seven species were found on both continents, consistent with previous reports of high continental endemism within the genus. Presently it is not possible to tell whether the transoceanic disjunctions were due to human activities, migration across a Bering land bridge or long-distance dispersal.In an effort to stabilize the taxonomy, due in part to the recent publication of synonyms for 11 of the species, accepted names are presented together with their corresponding later synonyms. A new subclade that includes holotypes of M. castanea and M. brunneorosea is identified in sect. Morchella (Esculenta Clade). Lectotypes for Morchella deliciosa, M. eximia and M. tridentina are designated here, as well as epitypes for M. dunalii, M. eximia, M. purpurascens and M. vulgaris. Morchella conica was determined to be illegitimate, and further research is required to determine the identity of M. elata and M. inamoena.
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