TY - JOUR
T1 - Functional modeling identifies paralogous solanesyl-diphosphate synthases that assemble the side chain of plastoquinone-9 in plastids
AU - Block, Anna
AU - Fristedt, Rikard
AU - Rogers, Sara
AU - Kumar, Jyothi
AU - Barnes, Brian
AU - Barnes, Joshua
AU - Elowsky, Christian G.
AU - Wamboldt, Yashitola
AU - Mackenzie, Sally A.
AU - Redding, Kevin
AU - Merchant, Sabeeha S.
AU - Basset, Gilles J.
PY - 2013/9/20
Y1 - 2013/9/20
N2 - It is a little known fact that plastoquinone-9, a vital redox cofactor of photosynthesis, doubles as a precursor for the biosynthesis of a vitamin E analog called plastochromanol-8, the physiological significance of which has remained elusive. Gene network reconstruction, GFP fusion experiments, and targeted metabolite profiling of insertion mutants indicated that Arabidopsis possesses two paralogous solanesyl-diphosphate synthases, AtSPS1 (At1g78510) and AtSPS2 (At1g17050), that assemble the side chain of plastoquinone-9 in plastids. Similar paralogous pairs were detected throughout terrestrial plant lineages but were not distinguished in the literature and genomic databases from mitochondrial homologs involvedin the biosynthesis of ubiquinone. The leaves of the atsps2 knock-out were devoidofplastochromanol-8 and displayed severe lossesofboth non-photoactive and photoactive plastoquinone-9, resulting in near complete photoinhibition at high light intensity. Such a photoinhibition was paralleled by significant damage to photosystem II but not to photosystem I. In contrast, in the atsps1 knock-out, a small loss of plastoquinone-9, restricted to the non-photoactive pool, was sufficient to eliminate half of the plastochromanol-8 content of the leaves. Taken together, these results demonstrate that plastochromanol-8 originates from a subfraction of the non-photoactive pool of plastoquinone-9. In contrast to other plastochromanol-8 biosynthetic mutants, neither the single atsps knock-outs nor the atsps1 atsps2 double knock-out displayed any defectsintocopherols accumulation or germination.
AB - It is a little known fact that plastoquinone-9, a vital redox cofactor of photosynthesis, doubles as a precursor for the biosynthesis of a vitamin E analog called plastochromanol-8, the physiological significance of which has remained elusive. Gene network reconstruction, GFP fusion experiments, and targeted metabolite profiling of insertion mutants indicated that Arabidopsis possesses two paralogous solanesyl-diphosphate synthases, AtSPS1 (At1g78510) and AtSPS2 (At1g17050), that assemble the side chain of plastoquinone-9 in plastids. Similar paralogous pairs were detected throughout terrestrial plant lineages but were not distinguished in the literature and genomic databases from mitochondrial homologs involvedin the biosynthesis of ubiquinone. The leaves of the atsps2 knock-out were devoidofplastochromanol-8 and displayed severe lossesofboth non-photoactive and photoactive plastoquinone-9, resulting in near complete photoinhibition at high light intensity. Such a photoinhibition was paralleled by significant damage to photosystem II but not to photosystem I. In contrast, in the atsps1 knock-out, a small loss of plastoquinone-9, restricted to the non-photoactive pool, was sufficient to eliminate half of the plastochromanol-8 content of the leaves. Taken together, these results demonstrate that plastochromanol-8 originates from a subfraction of the non-photoactive pool of plastoquinone-9. In contrast to other plastochromanol-8 biosynthetic mutants, neither the single atsps knock-outs nor the atsps1 atsps2 double knock-out displayed any defectsintocopherols accumulation or germination.
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U2 - 10.1074/jbc.M113.492769
DO - 10.1074/jbc.M113.492769
M3 - Article
C2 - 23913686
AN - SCOPUS:84884563750
SN - 0021-9258
VL - 288
SP - 27594
EP - 27606
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 38
ER -