Departamento de Ingeniería Genética de Plantas, Unidad Irapuato, Centro de Investigación y de Estudios Avanzados del IPN, 36500 Irapuato, Guanajuato, Mexico.
Fungal Genet Biol. 2012 Oct;49(10):765-71. doi: 10.1016/j.fgb.2012.07.005. Epub 2012 Aug 16.
Ustilago maydis (DC) Cda., a phytopathogenic Basidiomycota, is the causal agent of corn smut. During its life cycle U. maydis alternates between a yeast-like, haploid nonpathogenic stage, and a filamentous, dikaryotic pathogenic form that invades the plant and induces tumor formation. As all the members of the Subphylum Ustilaginomycotina, U. maydis is unable to form basidiocarps, instead it produces teliospores within the tumors that germinate forming a septate basidium (phragmobasidium). We have now established conditions allowing a completely different developmental program of U. maydis when grown on solid medium containing auxins in dual cultures with maize embryogenic calli. Under these conditions U. maydis forms large hemi-spheroidal structures with all the morphological and structural characteristics of gastroid-type basidiocarps. These basidiocarps are made of three distinct hyphal layers, the most internal of which (hymenium) contains non-septate basidia (holobasidia) from which four basidiospores develop. In basidiocarps meiosis and genetic recombination occur, and meiotic products (basidiospores) segregate in a Mendelian fashion. These results are evidence of sexual cycle completion of an Ustilaginomycotina in vitro, and the demonstration that, besides its quasi-obligate biotrophic pathogenic mode of life, U. maydis possesses the genetic program to form basidiocarps as occurs in saprophytic Basidiomycota species.
玉米黑粉菌（DC）Cda.，一种植物病原担子菌，是玉米黑粉病的病原体。在其生命周期中，玉米黑粉菌在酵母样、单倍体非致病性阶段和丝状、双核致病性形式之间交替，后者侵入植物并诱导肿瘤形成。与所有子囊菌亚门的成员一样，玉米黑粉菌无法形成担子果，而是在肿瘤内产生厚垣孢子，这些厚垣孢子萌发形成有隔膜的担子（phragmobasidium）。我们现在已经建立了条件，允许玉米黑粉菌在含有植物生长素的固体培养基上与玉米胚胎性愈伤组织进行双培养时，遵循一个完全不同的发育程序。在这些条件下，玉米黑粉菌形成具有所有腹菌类担子果形态和结构特征的大型半球形结构。这些担子果由三个不同的菌丝层组成，最内层（子实层）含有不分隔的担子（holobasidia），从中发育出四个担孢子。在担子果中发生减数分裂和遗传重组，减数分裂产物（担孢子）以孟德尔方式分离。这些结果证明了 Ustilaginomycotina 在体外完成了有性循环，并且证明除了其准专性生物营养性致病生活方式外，玉米黑粉菌还具有形成担子果的遗传程序，这与腐生担子菌物种中发生的情况相同。
