Université de Lyon, France.
Biochem J. 2010 Mar 29;427(2):323-32. doi: 10.1042/BJ20091813.
In order to redefine the mannitol pathway in the necrotrophic plant pathogen Botrytis cinerea, we used a targeted deletion strategy of genes encoding two proteins of mannitol metabolism, BcMTDH (B. cinerea mannitol dehydrogenase) and BcMPD (B. cinerea mannitol-1-phosphate dehydrogenase). Mobilization of mannitol and quantification of Bcmpd and Bcmtdh gene transcripts during development and osmotic stress confirmed a role for mannitol as a temporary and disposable carbon storage compound. In order to study metabolic fluxes, we followed conversion of labelled hexoses in wild-type and DeltaBcmpd and DeltaBcmtdh mutant strains by in vivo NMR spectroscopy. Our results revealed that glucose and fructose were metabolized via the BcMPD and BcMTDH pathways respectively. The existence of a novel mannitol phosphorylation pathway was also suggested by the NMR investigations. This last finding definitively challenged the existence of the originally postulated mannitol cycle in favour of two simultaneously expressed pathways. Finally, physiological and biochemical studies conducted on double deletion mutants (DeltaBcmpdDeltaBcmtdh) showed that mannitol was still produced despite a complete alteration of both mannitol biosynthesis pathways. This strongly suggests that one or several additional undescribed pathways could participate in mannitol metabolism in B. cinerea.
为了重新定义坏死性植物病原体 Botrytis cinerea 中的甘露醇途径，我们使用了靶向缺失编码甘露醇代谢两种蛋白的基因的策略，即 BcMTDH（Botrytis cinerea 甘露醇脱氢酶）和 BcMPD（Botrytis cinerea 甘露醇-1-磷酸脱氢酶）。甘露醇的动员以及 Bcmpd 和 Bcmtdh 基因转录本在发育和渗透胁迫期间的定量证实了甘露醇作为临时和可处置碳储存化合物的作用。为了研究代谢通量，我们通过体内 NMR 光谱法跟踪野生型和ΔBcmpd 和ΔBcmtdh 突变株中标记己糖的转化。我们的结果表明，葡萄糖和果糖分别通过 BcMPD 和 BcMTDH 途径代谢。NMR 研究还表明存在一种新的甘露醇磷酸化途径。这一最后发现明确挑战了最初假设的甘露醇循环的存在，而有利于同时表达的两种途径。最后，对双缺失突变体（ΔBcmpdΔBcmtdh）进行的生理和生化研究表明，尽管两种甘露醇生物合成途径都完全改变，但仍能产生甘露醇。这强烈表明一个或几个未描述的途径可能参与 Botrytis cinerea 中的甘露醇代谢。
