Krämer Moritz, Dörfer Eva, Hickl Daniel, Bellin Leo, Scherer Vanessa, Möhlmann Torsten
Plant Physiology, Faculty of Biology, University of Kaiserslautern, Kaiserslautern, Germany.
Front Plant Sci. 2022 Mar 10;13:842156. doi: 10.3389/fpls.2022.842156. eCollection 2022.
Cytidine triphosphate synthase (CTPS) catalyzes the final step in pyrimidine synthesis. In Arabidopsis, this protein family consists of five members (CTPS1-5), and all of them localize to the cytosol. Specifically, showed a massive upregulation of transcript levels during abiotic stress, in line with increased staining of promoter:GUS lines in hypocotyl, root and to lesser extend leaf tissues. In a setup to study progressive drought stress, knockout mutants accumulated less fresh and dry weight at days 5-7 and showed impaired ability to recover from this stress after 3 days of rewatering. Surprisingly, a thorough physiological characterization of corresponding plants only revealed alterations in assimilation and accumulation of soluble sugars including those related to drought stress in the mutant. Bimolecular fluorescence complementation (BiFC) studies indicated the interaction of CTPS4 with other isoforms, possibly affecting cytoophidia (filaments formed by CTPS formation. Although the function of these structures has not been thoroughly investigated in plants, altered enzyme activity and effects on cell structure are reported in other organisms. CTPS activity is required for cell cycle progression and growth. Furthermore, drought can lead to the accumulation of reactive oxygen species (ROS) and by this, to DNA damage. We hypothesize that effects on the cell cycle or DNA repair might be relevant for the observed impaired reduced drought stress tolerance of mutants.
胞苷三磷酸合成酶（CTPS）催化嘧啶合成的最后一步。在拟南芥中，这个蛋白质家族由五个成员（CTPS1 - 5）组成，它们都定位于细胞质中。具体而言，在非生物胁迫期间，其转录水平出现大量上调，这与下胚轴、根以及程度较轻的叶组织中启动子：GUS系的染色增加一致。在一项研究渐进性干旱胁迫的实验中，CTPS敲除突变体在第5 - 7天积累的鲜重和干重较少，并且在重新浇水3天后从这种胁迫中恢复的能力受损。令人惊讶的是，对相应植株进行全面的生理特征分析仅发现了同化作用和可溶性糖积累的改变，包括与突变体干旱胁迫相关的那些改变。双分子荧光互补（BiFC）研究表明CTPS4与其他同工型相互作用，可能影响细胞蛇（由CTPS形成的细丝）。尽管这些结构在植物中的功能尚未得到充分研究，但在其他生物体中已报道了酶活性的改变和对细胞结构的影响。CTPS活性是细胞周期进程和生长所必需的。此外，干旱会导致活性氧（ROS）的积累，进而导致DNA损伤。我们推测，对细胞周期或DNA修复的影响可能与观察到的CTPS突变体干旱胁迫耐受性降低受损有关。
