白桦是一种具有较高经济价值的亚热带速生用材树种。然而,随着全球变暖,热应力成为限制光亮双歧杆菌生产力的主要环境变量之一,不同地理种群对高温的反应尚不清楚。为了全面了解B.luminifera在热应激下的行为,在这项工作中,以综合的观点描述了六个流明芽孢杆菌种群(跨核心分布区域)的生理反应。结果表明,光明双歧杆菌可能存在多层次的生理调控网络,第一个反应是抗性酶的活性[例如,过氧化物酶(POD)]在2小时热胁迫的初步阶段,然后脯氨酸(渗透调节物质)含量在连续高温处理24h后开始增加。此外,光合作用受到热胁迫的强烈影响,在热处理下,所有六个发光双歧杆菌种群的净光合速率(Pn)均呈下降趋势。有趣的是,尽管六个流明双歧杆菌种群的生理变化模式在相同参数下相对一致,不同人群之间存在明显差异。综合分析表明,融水(RS)的生理反应最为稳定,这是代表性的B.luminifera种群。IlluminaRNA-seq分析应用RS种群揭示了热应激下光亮芽孢杆菌的特定生物学过程,共获得116,484个单基因。在34个KEGG通路中富集了热胁迫下不同时间段之间的差异表达基因(DEGs),在所有成对比较中,柠檬烯和pin烯降解途径通常被富集。此外,转录因子包括bHLH(碱性螺旋-环-螺旋),MYB,WRKY,和NAC(NAM,鉴定了ATAF1/2和CUC2)。在这项研究中,揭示了光亮双歧杆菌在高温胁迫下的生理反应和耐受机制,可为光亮芽孢杆菌的选择和抗性评价奠定基础,为栽培育种奠定基础。
Betula luminifera is a subtropical fast-growing timber species with high economic value. However, along with global warming, heat stress become one of the main environmental variables that limit the productivity of B. luminifera, and the response of diverse geographic
populations to high temperatures is still unclear. In order to offer a comprehensive understanding of the behavior of B. luminifera under heat stress, the physiological responses of six B. luminifera
populations (across the core distribution area) were described in this work in an integrated viewpoint. The results showed that a multi-level physiological regulatory network may exist in B. luminifera, the first response was the activity of resistant enzymes [e.g., peroxidase (POD)] at a preliminary stage of 2 h heat stress, and then the proline (osmoregulation substance) content began to increase after 24 h of continuous high-temperature treatment. In addition, photosynthesis was stronlgly affected by heat stress, and the net photosynthetic rate (Pn ) showed a downward trend under heat treatment in all six B. luminifera
populations. Interestingly, although the physiological change patterns of the six B. luminifera
populations were relatively consistent for the same parameter, there were obvious differences among different
populations. Comprehensive analysis revealed that the physiological response of Rongshui (RS) was the most stable, and this was the representative B. luminifera population. Illumina RNA-seq analysis was applied to reveal the specific biological process of B. luminifera under heat stress using the RS population, and a total of 116,484 unigenes were obtained. The differentially expressed genes (DEGs) between different time periods under heat stress were enriched in 34 KEGG pathways, and the limonene and pinene degradation pathway was commonly enriched in all pairwise comparisons. Moreover, transcription factors including bHLH (basic helix-loop-helix), MYB, WRKY, and NAC (NAM, ATAF1/2, and CUC2) were identified. In this study, the physiological response and tolerance mechanisms of B. luminifera under high temperature stress were revealed, which can conducive to the basis of B. luminifera selection and resistance assessment for cultivation and breeding.