Departamento de Ingeniería Genética, Unidad Irapuato, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Irapuato, Guanajuato, Mexico.
FEMS Yeast Res. 2010 Nov;10(7):928-40. doi: 10.1111/j.1567-1364.2010.00675.x. Epub 2010 Sep 14.
In previous communications the essential role of spermidine in Ustilago maydis was demonstrated by means of the disruption of the genes encoding ornithine decarboxylase (ODC) and spermidine synthase (SPE). However, the assignation of specific roles to each polyamine in different cellular functions was not possible because the spermidine added to satisfy the auxotrophic requirement of odc/spe double mutants is partly back converted into putrescine. In this study, we have approached this problem through the disruption of the gene-encoding polyamine oxidase (PAO), required for the conversion of spermidine into putrescine, and the construction of odc/pao double mutants that were unable to synthesize putrescine by either ornithine decarboxylation or retroconversion from spermidine. Phenotypic analysis of the mutants provided evidence that putrescine is only an intermediary in spermidine biosynthesis, and has no direct role in cell growth, dimorphic transition, or any other vital function of U. maydis. Nevertheless, our results show that putrescine may play a role in the protection of U. maydis against salt and osmotic stress, and possibly virulence. Evidence was also obtained that the retroconversion of spermidine into putrescine is not essential for U. maydis growth but may be important for its survival under natural conditions.
在之前的交流中，通过破坏编码鸟氨酸脱羧酶 (ODC) 和精脒合酶 (SPE) 的基因，证明了精脒在构巢曲霉中的重要作用。然而，由于添加的精脒来满足 odc/spe 双突变体的营养需求，部分会回转化为腐胺，因此无法为不同细胞功能中的每种多胺分配特定的角色。在这项研究中，我们通过破坏编码多胺氧化酶 (PAO) 的基因来解决这个问题，该基因是将精脒转化为腐胺所必需的，并且构建了 odc/pao 双突变体，这些突变体既不能通过鸟氨酸脱羧，也不能通过从精脒的逆行转化来合成腐胺。对突变体的表型分析提供了证据，证明腐胺只是精脒生物合成的中间产物，而在细胞生长、二态性转变或构巢曲霉的任何其他重要功能中没有直接作用。尽管如此，我们的结果表明腐胺可能在保护构巢曲霉免受盐和渗透胁迫以及可能的毒力方面发挥作用。还获得了证据表明，精脒向腐胺的逆行转化对于构巢曲霉的生长不是必需的，但对于其在自然条件下的生存可能很重要。
