The hydroxyphenylpyruvate dioxygenase from Synechocystis sp. PCC 6803 is not required for plastoquinone biosynthesis

Abstract

The disruption of the Synechocystis open reading frame v vslr0090 encoding a gene with high homology to plant genes encoding 4-hydroxyphenylpyruvate dioxygenase results in an impairment of tocopherol biosynthesis without a¡ecting levels of plastoquinone, carotenoids and chlorophyll as well as cell growth and photosynthesis. Our results indicate that in Synechocystis in contrast to the situation in higher plants the 4-hydroxyphenylpyruvate dioxygenase is not required for the synthesis of plastoquinone. ß

Chorismate Pyruvate-Lyase and 4-Hydroxy-3-solanesylbenzoate Decarboxylase Are Required for Plastoquinone Biosynthesis in the Cyanobacterium Synechocystis sp. PCC6803

“…Previous studies indicated that cyanobacteria possess an alternative PQ biosynthetic pathway compared with the one in higher plants (6,8). Here, we continued our studies on Synechocystis sp.…”

“…PQ synthesis in Synechocystis sp. PCC 6803 was, in contrast, found to proceed independently of hydroxyphenylpyruvate dioxygenase activity for homogentisate production (6). This suggested that the cyanobacterium uses an alternative or additional pathway for the formation of PQ in comparison to plants.…”

“…This prenylquinone plays a central role in photosynthesis. It functions primarily as an electron carrier of the photosynthetic electron transport chain in thylakoid membranes of plants and cyanobacteria where it transfers electrons from the photosystem II reaction center to the cytochrome b 6 f complex. Similarly to PQ in thylakoid membranes, ubiquinone functions as a mobile electron carrier in respiratory electron transport chains located in the plasma membrane of most aerobic bacteria and in the inner mitochondrial membranes of eukaryotes.…”

“…Interestingly, the Synechocystis sp. genome was predicted to encode homologs to some of the Escherichia coli proteins involved in ubiquinone biosynthesis, which probably contribute to PQ biosynthesis (6). Studies on the biosynthesis and role of PQ in cyanobacteria were, however, prevented by difficulties in generating complete loss of function mutants in candidate genes (1,7).…”

Proteomics Analysis of Drought Stress-Responsive Proteins in Hippophae rhamnoides L.

“…The HPPD participates in tyrosine catabolism and is involved in the biosynthesis of plastoquinones and tocopherols (Norris et al 1995;Collakova and DellaPenna 2003;Rippert et al 2004). In plants, plastoquinone serves as an electron carrier between photosystem (PS) II and the cytochrome b6/f complex (Dahnhardt et al 2002), while tocopherols can function as lipophilic antioxidants or play a nonantioxidant regulatory role in photosynthesis and macronutrient homeostasis through a signal transduction pathway (Sakuragi et al 2006). Falk et al (2002) also reported that the accumulation of AOS can stimulate the expression of the hppd gene.…”