Abstract：
Hypocrellin A (HA) is an excellent perylenequinone photosensitizer from Shiraia fruiting bodies. A dominant bacterium Pseudomonas fulva SB1 in the fruiting body was found to promote HA biosynthesis. The bacterial LPS were purified and the O-specific polysaccharide (OPS) consisted of rhamnose (Rha), galactose (Gal) and N-acetyl-galactosamine (GalNAc) with an average molecular weight of 282.8 kDa. Although the OPS composing of Rhap and Galp backbone showed elicitation capability on fungal HA accumulation, the highest HA production (303.76 mg/L) was achieved by LPS treatment at 20 μg/mL on day 3 of the mycelium culture. The generation of nitric oxide (NO) in Shiraia mycelia was triggered by LPS, which was partially blocked by inhibitors of nitric oxide synthase (NOS) and nitrate reductase (NR), leading to the depressed HA production. Transcriptome analysis revealed that NO mediated LPS-induced HA production via upregulating the expressions of critical genes associated with central carbon metabolism and downstream HA biosynthesis genes. This is the first report of LPS-induced NO to regulate fungal secondary metabolite production, which provides new insights on the role of bacterial LPS in bacterium-fungus interactions and an effective strategy to enhance hypocrellin production.
摘要：
竹红菌素A（HA）是一种来自Shiraia子实体的优异的perylenequinone光敏剂。发现子实体中的优势细菌假单胞菌SB1可促进HA的生物合成。纯化细菌LPS，O-特异性多糖（OPS）由鼠李糖（Rha）组成，半乳糖（Gal）和N-乙酰基-半乳糖胺（GalNAc），平均分子量为282.8kDa。尽管由Rhap和Galp主链组成的OPS显示出对真菌HA积累的诱导能力，在菌丝体培养的第3天，通过以20μg/mL的LPS处理实现了最高的HA产量（303.76mg/L）。一氧化氮(NO)在Shiraia菌丝体中的产生是由LPS引发的,部分被一氧化氮合酶（NOS）和硝酸还原酶（NR）的抑制剂阻断，导致HA产量下降。转录组分析表明，NO通过上调与中心碳代谢相关的关键基因和下游HA生物合成基因的表达来介导LPS诱导的HA产生。这是LPS诱导的NO调节真菌次级代谢产物的首次报道，这为细菌LPS在细菌-真菌相互作用中的作用提供了新的见解，并提供了一种有效的策略来增强hyporillin的生产。
