Table_9_Cellular response of Parachlorella kessleri to a solid surface culture environment.xlsx

Attached culture allows high biomass productivity and is a promising biomass cultivating system because neither a huge facility area nor a large volume of culture medium are needed. This study investigates photosynthetic and transcriptomic behaviors in Parachlorella kessleri cells on a solid surface after their transfer from liquid culture to elucidate the physiological and gene-expression regulatory mechanisms that underlie their vigorous proliferation. The chlorophyll content shows a decrease at 12 h after the transfer; however, it has fully recovered at 24 h, suggesting temporary decreases in the amounts of light harvesting complexes. On PAM analysis, it is demonstrated that the effective quantum yield of PSII decreases at 0 h right after the transfer, followed by its recovery in the next 24 h. A similar changing pattern is observed for the photochemical quenching, with the PSII maximum quantum yield remaining at an almost unaltered level. Non-photochemical quenching was increased at both 0 h and 12 h after the transfer. These observations suggest that electron transfer downstream of PSII but not PSII itself is only temporarily damaged in solid-surface cells just after the transfer, with light energy in excess being dissipated as heat for PSII protection. It thus seems that the photosynthetic machinery acclimates to high-light and/or dehydration stresses through its temporal size-down and functional regulation that start right after the transfer. Meanwhile, transcriptomic analysis by RNA-Seq demonstrates temporary upregulation at 12 h after the transfer as to the expression levels of many genes for photosynthesis, amino acid synthesis, general stress response, and ribosomal subunit proteins. These findings suggest that cells transferred to a solid surface become stressed immediately after transfer but can recover their high photosynthetic activity through adaptation of photosynthetic machinery and metabolic flow as well as induction of general stress response mechanisms within 24 h.

附着的培养系统因其无需庞大的设施面积及大量培养基而具备高生物量生产力，从而成为极具潜力的生物质栽培体系。本研究旨在探究在将 Parachlorella kessleri 细胞从液态培养转移到固体表面后，其光合作用和转录组行为的变化，以阐明支撑其旺盛增殖的生理和基因表达调控机制。在转移后12小时，叶绿素含量出现下降，但至24小时已完全恢复，表明光捕获复合物的数量暂时减少。在 PAM 分析中，PSII 的有效量子产率在转移后的0小时下降，随后在接下来的24小时内恢复。光化学猝灭也呈现相似的变化模式，PSII 的最大量子产率保持在几乎未变的水准。非光化学猝灭在转移后的0小时和12小时均有所增加。这些观察结果表明，在转移后，固体表面细胞中 PSII 之后的电子传递途径而非 PSII 本身仅暂时受损，多余的光能以热能形式耗散，以保护 PSII。因此，光合作用机制似乎通过转移后的即时时间缩小和功能调控，适应了高光和/或脱水的压力。同时，通过 RNA-Seq 的转录组分析显示，转移后12小时，许多与光合作用、氨基酸合成、一般应激反应和核糖体亚基蛋白相关的基因表达水平出现暂时上调。这些发现表明，转移到固体表面的细胞在转移后立即承受压力，但可以通过光合作用机制和代谢流的适应以及24小时内一般应激反应机制的诱导，在24小时内恢复其高光合活性。