Institute of Bioinformatics, University of Georgia, Athens, USA.
School of Forestry and Natural Resources, University of Georgia, Athens, USA.
Plant Signal Behav. 2021 Nov 2;16(11):1976546. doi: 10.1080/15592324.2021.1976546. Epub 2021 Sep 13.
Phylloquinone (vitamin K1) is a thylakoid-embedded electron carrier essential for photosynthesis. Paradoxically, we found that phylloquinone biosynthesis is retained in the nonphotosynthetic holoparasite (Egyptian broomrape). The phylloquinone pathway genes are preferentially expressed during development of the invasive organ, the haustorium, and exhibit strong coexpression with redox-active proteins known to be involved in parasitism. Unlike in photoautotrophic taxa, the late pathway genes of the holoparasite lack the chloroplast-targeting sequence and their proteins are targeted to the plasma membrane instead. Plasma membrane phylloquinone may enable to sense changes in the redox environment during host interactions. The N-truncated isoforms are conserved in several other Orobanchaceae root holoparasites, and interestingly, in a number of closely related photoautotrophic species as well. This suggests an ancient origin of distinct phylloquinone pathways predating the evolution of parasitic plants in the Orobanchaceae. These findings represent exciting opportunities to probe plasma membrane phylloquinone function and diversification in parasitic and nonparasitic plant responses to external redox chemistry in the rhizosphere.
叶绿醌（维生素 K1）是一种位于类囊体中的电子载体，对光合作用至关重要。矛盾的是，我们发现非光合全寄生植物（埃及菫菜）中保留了叶绿醌的生物合成。叶绿醌途径基因在侵入器官吸器的发育过程中优先表达，并与已知参与寄生作用的氧化还原活性蛋白强烈共表达。与光合自养类群不同，全寄生植物途径基因的晚期缺乏质体靶向序列，其蛋白被靶向到质膜。质膜叶绿醌可能使它能够在与宿主相互作用过程中感知氧化还原环境的变化。N 端截断的同工型在其他几种 Orobanchaceae 根全寄生植物中是保守的，有趣的是，在一些密切相关的光合自养物种中也是如此。这表明，在 Orobanchaceae 寄生植物进化之前，就已经存在独特的叶绿醌途径的古老起源。这些发现为研究质膜叶绿醌在寄生和非寄生植物对根际外部氧化还原化学的反应中的功能和多样化提供了令人兴奋的机会。
