Glucose-6-Phosphate Dehydrogenase Modulates Shiraia Hypocrellin A Biosynthesis Through ROS/NO Signaling in Response to Bamboo Polysaccharide Elicitation

Hypocrellin A (HA), a photodynamic perylenequinone pigment from <i>Shiraia</i> fruiting bodies, functions as an efficient photosensitizer for clinical photodynamic therapy. Glucose-6-phosphate dehydrogenase (G6PDH), the rate-limiting enzyme of the pentose phosphate pathway (PPP), governs carbon flux into NADPH production. This study elucidates G6PDH's regulatory role in HA biosynthesis in <i>Shiraia</i> sp. S9. Bamboo polysaccharide (BPS) elicitation (100 mg/L) significantly enhanced HA production to 428.1 mg/L, 1.6-fold higher than controls after 5 days. We cloned the <i>G6PDH</i> gene and demonstrated that BPS upregulated its expression and activity, concomitant with increased reactive oxygen species (ROS; H₂O₂ and O₂^•-) and nitric oxide (NO) generation. ROS production was mediated by NADPH oxidase induction, while NO generation was attributed to elevated nitric oxide synthase and nitrate reductase activities. Critically, the G6PDH inhibitor glucosamine (1.0 mM) suppressed both H₂O₂ and NO production. These ROS/NO signals upregulated key HA biosynthetic (<i>PKS</i>, <i>Omef</i>) and transport (<i>MFS</i>) genes. Our findings establish G6PDH as a central regulator of BPS-induced HA biosynthesis via ROS/NO signaling, revealing novel metabolic crosstalk between the PPP and fungal perylenequinone biosynthesis. This work presents BPS elicitation as a biotechnological strategy for scalable HA production in <i>Shiraia</i> mycelium cultures.