Analysis of the physiological role of Yang-cycle enzymes

阳循环酶的生理作用分析

• 批准号: 213107540
• 负责人: Professor Dr. Norbert Sauer
• 金额: --
• 依托单位: Department Biologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2012
• 资助国家: 德国
• 起止时间: 2011-12-31 至 2016-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/213107540?language=en
• 关键词: Analysis; physiological; role; Yang; cycle

During analyses of the Plantago major (common plantain) source-leaf vascular transcriptom we identified an unexpectedly high number of transcripts proteins involved in the biosynthesis of polyamines. Even more surprising was the identification of the vascular-specific expression of the gene for a methylthioribose kinase, PmMTK1, a protein of the Yang-cycle. As MTK1 is a unigene in Arabidopsis, and as we could not identify a second MTK gene in Plantago, we speculated that the vascular-specificity of one step of the Yang-cycle indicates vascular-specificity for all other reactions of the cycle as well. We could confirm this hypothesis and identified all but one of the yet unidentified Yang-cycle genes in higher plants, MTI1 and DEP1. Nevertheless, the physiological role of the Yang-cycle in Arabidopsis remains not well understood. Under normal growth conditions, Yang-cycle mutants grow like WT plants; developmental defects are observed only under un-physiological growth conditions with 5-methylthioadenosine (MTA; a cytotoxic Yang-cycle intermediate) as sole sulfur source. Here we propose experiments that (A) address the question after the reason for the vascular-specificity of the Yang-cycle and that (B) focus on physiological growth conditions that challenge Yang-cycle activity. We will also (C) perform a search for the final un-identified Yang-cycle enzyme and for a putative MTA transporter. With the proposed work we aim to elucidate the physiological role(s) of the Yang-cycle and to characterize its specific importance for polyamine and nicotianamine biosynthesis.

在对大车前草（普通车前草）源叶维管转录子的分析中，我们意外地发现了大量参与多胺生物合成的转录蛋白。更令人惊讶的是鉴定出甲基硫核糖激酶基因的血管特异性表达，PmMTK1是阳循环的一种蛋白质。由于MTK1在拟南芥中是一个单一基因，而我们无法在车前草中发现第二个MTK基因，我们推测阳循环中某一步的血管特异性也表明了阳循环中所有其他反应的血管特异性。我们可以证实这一假设，并确定了高等植物中除MTI1和DEP1外的所有尚未确定的阳循环基因。然而，阳循环在拟南芥中的生理作用尚不清楚。在正常生长条件下，阳循环突变体与WT植物生长相似；发育缺陷仅在以5-甲基硫代腺苷（MTA，一种细胞毒性阳循环中间体）为唯一硫源的非生理性生长条件下观察到。在这里，我们提出实验：(A)解决阳循环血管特异性的原因之后的问题，(B)关注挑战阳循环活动的生理生长条件。我们还将(C)对最终未鉴定的Yang-cycle酶和假定的MTA转运体进行搜索。我们的目的是阐明阳循环的生理作用，并描述其对多胺和烟胺生物合成的特殊重要性。