Department of Plant Pathology, University of Georgia, Athens, GA 30602, USA.
Fungal Genet Biol. 2013 Dec;61:111-9. doi: 10.1016/j.fgb.2013.09.002. Epub 2013 Sep 21.
Members of the fungal-specific velvet protein family regulate sexual and asexual spore production in the Ascomycota. We predicted, therefore, that velvet homologs in the basidiomycetous plant pathogen Ustilago maydis would regulate sexual spore development, which is also associated with plant disease progression in this fungus. To test this hypothesis, we studied the function of three U. maydis velvet genes, umv1, umv2 and umv3. Using a gene replacement strategy, deletion mutants were made in all three genes in compatible haploid strains, and additionally for umv1 and umv2 in the solopathogenic strain, SG200. None of the mutants showed novel morphological phenotypes during yeast-like, in vitro growth. However, the Δumv1 mutants failed to induce galls or teliospores in maize. Chlorazol black E staining of leaves infected with Δumv1 dikaryons revealed that the Δumv1 hyphae did not proliferate normally and were blocked developmentally before teliospore formation. The Δumv2 mutants were able to induce galls and teliospores in maize, but were slow to do so and thus reduced in virulence. The Δumv3 mutants were not affected in teliospore formation or disease progression. Complementation of the Δumv1 and Δumv2 mutations in the SG200 background produced disease indices similar to those of SG200. These results indicate that two U. maydis velvet family members, umv1 and umv2, are important for normal teliospore development and disease progression in maize seedlings.
真菌特异性 velvet 蛋白家族的成员调控子囊菌中的有性和无性孢子产生。因此，我们预测担子菌植物病原体玉米黑粉菌中的 velvet 同源物将调控有性孢子发育，这也与该真菌中植物疾病的进展相关。为了验证这一假说，我们研究了玉米黑粉菌的三个 velvet 基因 umv1、umv2 和 umv3 的功能。使用基因替换策略，在所有三个基因中都在相容的单倍体菌株中，以及在 solopathogenic 菌株 SG200 中，对 umv1 和 umv2 进行了缺失突变。在酵母样体外生长过程中，突变体没有表现出新颖的形态表型。然而，Δumv1 突变体未能在玉米中诱导瘿瘤或厚垣孢子。用 Chlorazol black E 对感染 Δumv1 双核体的叶片进行染色表明，Δumv1 菌丝不能正常增殖，在厚垣孢子形成之前发育受阻。Δumv2 突变体能在玉米中诱导瘿瘤和厚垣孢子，但诱导速度较慢，因此毒力降低。Δumv3 突变体在厚垣孢子形成或疾病进展方面不受影响。在 SG200 背景下对 Δumv1 和 Δumv2 突变的互补产生了与 SG200 相似的疾病指数。这些结果表明，玉米黑粉菌中的两个 velvet 家族成员 umv1 和 umv2 对正常厚垣孢子发育和玉米幼苗中的疾病进展很重要。
