Pucker Boas, Selmar Dirk
Institute of Plant Biology, TU Braunschweig, 38106 Braunschweig, Germany.
Braunschweig Integrated Centre of Systems Biology (BRICS), TU Braunschweig, 38106 Braunschweig, Germany.
Plants (Basel). 2022 Apr 1;11(7):963. doi: 10.3390/plants11070963.
Flavonoids are a biochemically diverse group of specialized metabolites in plants that are derived from phenylalanine. While the biosynthesis of the flavonoid aglycone is highly conserved across species and well characterized, numerous species-specific decoration steps and their relevance remained largely unexplored. The flavonoid biosynthesis takes place at the cytosolic side of the endoplasmatic reticulum (ER), but accumulation of various flavonoids was observed in the central vacuole. A universal explanation for the subcellular transport of flavonoids has eluded researchers for decades. Current knowledge suggests that a glutathione S-transferase-like protein (ligandin) protects anthocyanins and potentially proanthocyanidin precursors during the transport to the central vacuole. ABCC transporters and to a lower extend MATE transporters sequester anthocyanins into the vacuole. Glycosides of specific proanthocyanidin precursors are sequestered through MATE transporters. A P-ATPase in the tonoplast and potentially other proteins generate the proton gradient that is required for the MATE-mediated antiport. Vesicle-mediated transport of flavonoids from the ER to the vacuole is considered as an alternative or additional route.
黄酮类化合物是植物中一类生物化学性质多样的特殊代谢产物，由苯丙氨酸衍生而来。虽然黄酮苷元的生物合成在物种间高度保守且已得到充分表征，但许多物种特异性的修饰步骤及其相关性在很大程度上仍未得到探索。黄酮类化合物的生物合成发生在内质网（ER）的胞质侧，但在中央液泡中观察到了各种黄酮类化合物的积累。几十年来，研究人员一直未能找到关于黄酮类化合物亚细胞转运的普遍解释。目前的知识表明，一种谷胱甘肽S-转移酶样蛋白（配体蛋白）在花青素以及潜在的原花青素前体向中央液泡的转运过程中起到保护作用。ABCC转运蛋白以及程度较低的MATE转运蛋白将花青素隔离到液泡中。特定原花青素前体的糖苷通过MATE转运蛋白被隔离。液泡膜上的一种P-ATP酶以及可能的其他蛋白质产生了MATE介导的反向转运所需的质子梯度。黄酮类化合物从内质网到液泡的囊泡介导转运被认为是一种替代途径或额外途径。
