基于转录组与代谢组联合分析揭示香菇耐高温品系的响应机制

Abstract

Heat stress is the primary abiotic constraint on summer spawn-running and over-summer cultivation of shiitake (Lentinula edodes) in China. To dissect the molecular response mechanism of heat-tolerant strains and to serve marker-assisted breeding, a heat-tolerant strain LeR-07 and a heat-sensitive strain LeS-13 were subjected to 25 ℃ (control) and 40 ℃ treatments for 0, 4, 12 and 24 h. Mycelial growth, membrane injury and antioxidant enzyme activities were measured, and transcriptome (RNA-Seq) and untargeted metabolome (LC-MS/MS) analyses were integrated. The results showed that: (1) The semi-lethal temperatures (LT₅₀) of LeR-07 and LeS-13 were 38.6 ℃ and 34.2 ℃, respectively; after 24 h at 40 ℃ and 5 d recovery at 25 ℃, the recovery index was 82.4% for LeR-07 versus 34.6% for LeS-13. Relative electrolyte leakage and malondialdehyde content in LeR-07 were 31.4% and 39.2% lower than those in LeS-13 at 24 h. (2) A total of 4 862 differentially expressed genes were identified, of which 1 137 were specifically up-regulated in LeR-07 and significantly enriched in protein processing in endoplasmic reticulum, glutathione metabolism, arginine and proline metabolism, starch and sucrose metabolism, ABC transporters and MAPK signaling pathway. Genes encoding heat shock proteins (LeHSP20-3, LeHSP70-2, LeHSP90-1, LeHSP104), the heat shock transcription factor LeHSF1, the DnaJ-type co-chaperone LeDnaJ-07 and laccases LeLac4/LeLac7 were strongly induced in the tolerant strain, with a response peak approximately 8 h earlier than in the sensitive strain. (3) Six hundred and thirteen differentially accumulated metabolites were detected; trehalose, mannitol, γ-aminobutyric acid, proline, reduced glutathione and ergothioneine were markedly enriched in LeR-07. Integrated analysis co-mapped four pathways at both transcriptional and metabolic levels and identified five hub genes (LeTPS1, LeHSP20-3, LeGPX1, LeGST-2, LeABC2), among which LeTPS1 showed a correlation coefficient of 0.91 with trehalose content. (4) The heat-tolerant response of L. edodes can be summarized as a multi-layered process comprising rapid early perception, chaperone-mediated protection, antioxidant scavenging, osmotic and energy metabolic reprogramming, and rapid post-stress recovery. The decisive difference between tolerant and sensitive strains lies not in the intensity but in the onset speed and persistence of the response. A three-step breeding pipeline integrating a standardized evaluation system, target-gene marker development and conventional breeding is proposed, with LeTPS1, LeHSP20-3 and LeGPX1 recommended as positive selection markers and LeABC2 as a negative exclusion marker.