Dipartimento di Scienze Biomolecolari, Università degli Studi di Urbino Carlo Bo, via I Maggetti 26, 61029 Urbino (PU), Italy.
Curr Genet. 2010 Apr;56(2):109-19. doi: 10.1007/s00294-009-0284-4. Epub 2009 Dec 29.
The homocysteine synthase (tbhos) and putative sulfate transporter (tbsul1) genes have been characterized in order to understand the sulfate metabolism and regulation in the ectomycorrhizal fungus Tuber borchii. The analyses of tbsul1 and tbhos nucleotide and deduced amino acid sequences led to the identification of the typical domains shown in homologous proteins. Sulfate starvation condition upregulates both genes. The real-time PCR assay of tbsul1 revealed that gene expression was about threefold higher in mycelia grown under sulfate starvation for 2 days than in the mycelial control and in the same starvation condition, the sulfate uptake increased. Real-time PCR and enzymatic assays showed regulation of tbhos when sulfur sources were lacking, suggesting that a transcriptional regulation of this gene rather than a post-transcriptional one occurred. Furthermore, the tbsul1 and tbhos expression patterns were evaluated during the truffle life cycle, revealing an over-expression in the mature ascomata for both genes. In the ectomycorrhizal tissue, only tbhos was upregulated suggesting its substantial role in T. borchii cysteine synthesis. The regulation of tbsul1 and tbhos occurs primarily at the transcriptional level both during vegetative and fruiting phases and these genes could be directly involved in VOCs production.
为了了解外生菌根真菌块菌（Tuber borchii）中的硫酸盐代谢和调控，我们对其同型半胱氨酸合酶（tbhos）和假定硫酸盐转运蛋白（tbsul1）基因进行了特征分析。对 tbsul1 和 tbhos 的核苷酸和推导的氨基酸序列进行分析，确定了在同源蛋白中显示的典型结构域。硫酸盐饥饿条件上调了这两个基因。实时 PCR 分析显示，在硫酸盐饥饿培养 2 天后的菌丝中，tbsul1 的基因表达比菌丝对照高出约三倍，并且在相同的饥饿条件下，硫酸盐的摄取增加。实时 PCR 和酶活性测定表明，当缺乏硫源时，tbhos 受到调控，这表明该基因的转录调控而不是转录后调控。此外，在块菌的生命周期中评估了 tbsul1 和 tbhos 的表达模式，结果表明这两个基因在成熟的子实体中均有过表达。在外生菌根组织中，只有 tbhos 被上调，表明其在块菌半胱氨酸合成中具有重要作用。在营养和生殖阶段，tbsul1 和 tbhos 的调控主要发生在转录水平，这两个基因可能直接参与 VOCs 的产生。
