TY - JOUR
T1 - Sucrose synthases are not involved in starch synthesis in Arabidopsis leaves
AU - Fünfgeld, Maximilian M.F.F.
AU - Wang, Wei
AU - Ishihara, Hirofumi
AU - Arrivault, Stéphanie
AU - Feil, Regina
AU - Smith, Alison M.
AU - Stitt, Mark
AU - Lunn, John E.
AU - Niittylä, Totte
N1 - Funding Information:
We thank C. Abel for help with plant cultivation. This work was supported by a PhD fellowship (to M.M.F.F.F.) from the International Max Planck Research School ‘Primary Metabolism and Plant Growth’, the European Commission FP7 collaborative project TiMet (Contract No. 245143 to A.M.S. and M.S.), the Swedish Research Council for Sustainable Development (Formas) (project grant 2016-01322 to T.N.) and the Max Planck Society (H.I., S.A., R.F., M.S. and J.E.L.).
Funding Information:
We thank C. Abel for help with plant cultivation. This work was supported by a PhD fellowship (to M.M.F.F.F.) from the International Max Planck Research School ‘Primary Metabolism and Plant Growth’, the European Commission FP7 collaborative project TiMet (Contract No. 245143 to A.M.S. and M.S.), the Swedish Research Council for Sustainable Development (Formas) (project grant 2016-01322 to T.N.) and the Max Planck Society (H.I., S.A., R.F., M.S. and J.E.L.).
Publisher Copyright:
© 2022, The Author(s).
PY - 2022/5/28
Y1 - 2022/5/28
N2 - Many plants accumulate transitory starch reserves in their leaves during the day to buffer their carbohydrate supply against fluctuating light conditions, and to provide carbon and energy for survival at night. It is universally accepted that transitory starch is synthesized from ADP-glucose (ADPG) in the chloroplasts. However, the consensus that ADPG is made in the chloroplasts by ADPG pyrophosphorylase has been challenged by a controversial proposal that ADPG is made primarily in the cytosol, probably by sucrose synthase (SUS), and then imported into the chloroplasts. To resolve this long-standing controversy, we critically re-examined the experimental evidence that appears to conflict with the consensus pathway. We show that when precautions are taken to avoid artefactual changes during leaf sampling, Arabidopsis thaliana mutants that lack SUS activity in mesophyll cells (quadruple sus1234) or have no SUS activity (sextuple sus123456) have wild-type levels of ADPG and starch, while ADPG is 20 times lower in the pgm and adg1 mutants that are blocked in the consensus chloroplastic pathway of starch synthesis. We conclude that the ADPG needed for starch synthesis in leaves is synthesized primarily by ADPG pyrophosphorylase in the chloroplasts.
AB - Many plants accumulate transitory starch reserves in their leaves during the day to buffer their carbohydrate supply against fluctuating light conditions, and to provide carbon and energy for survival at night. It is universally accepted that transitory starch is synthesized from ADP-glucose (ADPG) in the chloroplasts. However, the consensus that ADPG is made in the chloroplasts by ADPG pyrophosphorylase has been challenged by a controversial proposal that ADPG is made primarily in the cytosol, probably by sucrose synthase (SUS), and then imported into the chloroplasts. To resolve this long-standing controversy, we critically re-examined the experimental evidence that appears to conflict with the consensus pathway. We show that when precautions are taken to avoid artefactual changes during leaf sampling, Arabidopsis thaliana mutants that lack SUS activity in mesophyll cells (quadruple sus1234) or have no SUS activity (sextuple sus123456) have wild-type levels of ADPG and starch, while ADPG is 20 times lower in the pgm and adg1 mutants that are blocked in the consensus chloroplastic pathway of starch synthesis. We conclude that the ADPG needed for starch synthesis in leaves is synthesized primarily by ADPG pyrophosphorylase in the chloroplasts.
UR - https://www.scopus.com/pages/publications/85128582215
UR - https://pubmed.ncbi.nlm.nih.gov/35484201
U2 - 10.1038/s41477-022-01140-y
DO - 10.1038/s41477-022-01140-y
M3 - Article
C2 - 35484201
AN - SCOPUS:85128582215
SN - 2055-026X
VL - 8
SP - 574
EP - 582
JO - Nature Plants
JF - Nature Plants
IS - 5
ER -