Evolution of plastid FAX (fatty acid export) proteins and the plants' conquest of land - molecular and metabolic adaptation

质体 FAX（脂肪酸输出）蛋白的进化和植物对陆地的征服 - 分子和代谢适应

• 批准号: 528100298
• 负责人: Professorin Dr. Katrin Philippar
• 金额: --
• 依托单位: Professur für Pflanzenbiologie
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/528100298?language=en
• 关键词: Evolution; plastid; FAX; fatty; acid

The colonization of land by descendants of freshwater algae was a watershed moment in earths’ history. Plants encountered many environmental challenges during the conquest of the land, such as desiccation, high intensity light, UV-radiation, lack of nutrient availability, mechanical damage, and pathogen infections. In consequence, a consecutive adaptation of metabolism and morphology took place during evolution of ancestors from early Streptophyte algae to todays seed plants. Among these versatile adjustments of land plant metabolism to terrestrial environments, changes in biosynthesis, distribution and homeostasis of lipids represent crucial steps to cope with stressful life. Fatty acid transport function of FAX (fatty acid export) proteins in the inner envelope membrane of chloroplasts has been shown to be crucial for cellular lipid homeostasis under normal and stress conditions such as cold acclimation in the model organisms Arabidopsis thaliana (seed plant) and Chlamydomonas reinhardtii (green micro alga). However, nothing is known about FAX proteins in the organisms relevant for first steps in plant terrestrialization. In order to close this gap and evaluate FAX protein evolution towards adjustment of metabolism to life on land, we aim to pinpoint molecular adaptation of plastid FAX proteins in bryophytes, i.e. in Physcomitrium patens and Marchantia polymorpha. With the emergence of the prominent apo-lipoprotein α-helix bundle at the N-terminus of plastid FAX that is conserved throughout evolution of monophyletic Phragmoplastophyta, we could already identify a crucial molecular element. Interestingly, the FAX apo domain is predicted to bridge the inner and outer envelope membrane of chloroplasts for fatty acid and lipid transport. Moreover, this domain is likely to mediate chloroplast-mitochondrium contacts for lipid exchange at phosphate starvation stress. Within the research project, we now aim to identify exact membrane topology, formation of hetero-oligomeric complexes as well as in planta function of apoFAX and FAX proteins in Physcomitrium patens and Marchantia polymorpha. In the spotlight is the role in adaptation of lipid metabolism in response to cold stress and mineral deficiency, namely phosphate and potassium starvation.

淡水藻类后代在陆地上的殖民是地球历史上的一个分水岭。植物在征服土地的过程中遇到了许多环境挑战，例如干燥、高强度光、紫外线辐射、缺乏养分、机械损伤和病原体感染。因此，在祖先从早期的链藻类藻类到今天的种子植物的进化过程中，新陈代谢和形态的连续适应发生了。在陆地植物代谢对陆地环境的这些多功能调整中，脂质生物合成、分布和稳态的变化代表了应对生活压力的关键步骤。叶绿体内膜中 FAX（脂肪酸输出）蛋白的脂肪酸转运功能已被证明对于正常和应激条件下的细胞脂质稳态至关重要，例如模式生物拟南芥（种子植物）和莱茵衣藻（绿微藻）的冷驯化。然而，对于与植物陆化第一步相关的生物体中的 FAX 蛋白一无所知。为了缩小这一差距并评估 FAX 蛋白进化以适应陆地生命的新陈代谢，我们的目标是查明苔藓植物（即立碗藓和地钱）中质体 FAX 蛋白的分子适应。随着质体 FAX N 端显着的脱辅基脂蛋白 α 螺旋束的出现（该螺旋束在单系Phragmoplastopphyta 的进化过程中一直保守），我们已经可以鉴定出一个关键的分子元件。有趣的是，FAX apo 结构域预计将桥接叶绿体的内膜和外膜，以进行脂肪酸和脂质的运输。此外，该结构域可能介导叶绿体-线粒体接触，以在磷酸盐饥饿应激下进行脂质交换。在该研究项目中，我们现在的目标是确定小立碗藓和地钱中 apoFAX 和 FAX 蛋白的确切膜拓扑结构、异源寡聚复合物的形成以及植物中的功能。人们关注的是脂质代谢适应寒冷应激和矿物质缺乏（即磷酸盐和钾饥饿）的作用。