Ye Zihao, Sawada Mina, Iwasa Makiko, Moriyama Ryo, Dey Debayan, Furutani Miyu, Kitao Mitsutoshi, Hara Toshihiko, Tanaka Ayumi, Kishimoto Junko, Yokono Makio, Akimoto Seiji, Takabayashi Atsushi, Tanaka Ryouichi
Institute of Low Temperature Science, Hokkaido University, Sapporo 060-0819, Japan.
Graduate School of Science, Kobe University, Kobe 657-8501, Japan.
J Exp Bot. 2025 Jan 10;76(2):513-531. doi: 10.1093/jxb/erae412.
Overwintering evergreen trees in boreal regions continuously convert absorbed light energy into heat through a process known as sustained thermal dissipation. To better understand this mechanism, this study examined the alterations in the photosynthetic apparatus and transcriptomes of yew (Taxus cuspidata) leaves throughout the year, comparing sun-exposed and shaded leaves. The Y(II) parameter, conventionally used to estimate the quantum yield of photosystem II (PSII), indicated the occurrence of temperature-dependent thermal dissipation during winter. On the other hand, the levels of photosystem subunits, including the D1 subunit of the PSII reaction center, remained relatively stable year-round, indicating that typical photoinhibition is unlikely to occur. Time-resolved chlorophyll fluorescence analysis revealed that heat dissipation at the PSII antenna is prominent in winter. Winter transcriptomes are notably characterized by a predominance of Elip transcripts encoding early light-induced protein (ELIP), which constitute 20% of the total transcripts, as deduced from RNA-seq analysis. Furthermore, ELIP protein concentration increased to nearly half that of the major light-harvesting complexes. The predicted structure of ELIP includes potential chlorophyll a and carotenoid binding sites. These findings, taken together with a previous report showing ELIP capacity for energy dissipation, lead to a re-evaluation of its significant role in sustained thermal dissipation.
北方地区的越冬常绿树通过一种称为持续热耗散的过程，不断将吸收的光能转化为热量。为了更好地理解这一机制，本研究对紫杉（东北红豆杉）叶片全年的光合机构和转录组变化进行了研究，比较了向阳叶和遮阴叶。传统上用于估计光系统II（PSII）量子产率的Y（II）参数表明，冬季存在温度依赖性热耗散。另一方面，包括PSII反应中心D1亚基在内的光系统亚基水平全年保持相对稳定，这表明不太可能发生典型的光抑制。时间分辨叶绿素荧光分析表明，冬季PSII天线处的热耗散较为突出。冬季转录组的显著特征是编码早期光诱导蛋白（ELIP）的Elip转录本占主导地位，根据RNA测序分析推断，其占总转录本的20%。此外，ELIP蛋白浓度增加到主要捕光复合体的近一半。ELIP的预测结构包括潜在的叶绿素a和类胡萝卜素结合位点。这些发现，再加上之前一份显示ELIP具有能量耗散能力的报告，促使人们重新评估其在持续热耗散中的重要作用。
