Ribosome biogenesis is a constitutive fundamental process for cellular function. Its rate of production depends on the rate of maturation of precursor rRNA (pre-rRNA). The rRNA maturation paths are characterized by four dominant rate-limiting intermediates with cell type variation of the processivity rate. We have identified that high temperature stress in plants, while halting the existing pre-rRNA maturation schemes, also transiently triggers an atypical pathway for 35S pre-rRNA processing. This pathway leads to production of an aberrant pre-rRNA, reminiscent of yeast 24S, encompassing 18S and 5.8S rRNAs that do not normally co-occur together at subunit levels; this response is elicited specifically by high and not low temperatures. We show this response to be conserved in two other model crop plant species (rice and tomato). This pathway persists even after returning to normal growth conditions for 1 h, and is reset between 1 h and 6 h after stress treatment, probably due to resumption of normal 35S pre-rRNA synthesis and processing. The heat-induced ITS2 cleavage-derived precursors and stalled P-A2-like precursors were heterogeneous in nature, with a fraction containing polymeric (A) tails. Furthermore, high temperature treatment and subsequent fractionation resulted in polysome and pre-rRNA depletion.

中文翻译：

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植物中rRNA成熟路径的动力学和热敏感性

核糖体生物发生是细胞功能的组成性基本过程。它的生产速度取决于前体 rRNA (pre-rRNA) 的成熟速度。rRNA 成熟路径的特点是四种主要的限速中间体，其中细胞类型的持续合成率变化。我们已经发现，植物中的高温胁迫在停止现有的 pre-rRNA 成熟方案的同时，也会暂时触发 35S pre-rRNA 加工的非典型途径。该途径导致异常前 rRNA 的产生，让人联想到酵母 24S，包括通常不会在亚基水平共存的 18S 和 5.8S rRNA；这种反应是由高温而不是低温引起的。我们表明这种反应在其他两种模式作物植物物种（水稻和番茄）中是保守的。该途径即使在恢复正常生长条件 1 小时后仍然存在，并且在应激处理后 1 小时至 6 小时之间重新设置，可能是由于恢复了正常的 35S 前 rRNA 合成和加工。热诱导的 ITS2 裂解衍生的前体和停滞的 P-A2 样前体本质上是异质的，其中一部分含有聚合物 (A) 尾巴。此外，高温处理和随后的分馏导致多核糖体和前 rRNA 耗尽。