Unraveling the role of transient starch in the response of Arabidopsis to elevated CO2 under long-day conditions

•Exposure to elevated CO2 has shown that starch synthesis can be involved in amelioration of photosynthetic downregulation under increasing CO2 conditions.•While elevated CO2 promoted growth of both wild type and aps1 (accompanied by an increased net rate of CO2 fixation), it had no effect on gwd pl...

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Bibliographic Details
Published in:Environmental and experimental botany 2018-11, Vol.155, p.158-164
Main Authors: Jauregui, Ivan, Pozueta-Romero, Javier, Córdoba, Javier, Avice, Jean-Christophe, Aparicio-Tejo, Pedro M, Baroja-Fernández, Edurne, Aranjuelo, Iker
Format: Article
Language:English
Subjects:
Elevated CO2
Growth
Life Sciences
Photosynthesis
Photosynthetic acclimation
Starch
Vegetal Biology
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Summary:•Exposure to elevated CO2 has shown that starch synthesis can be involved in amelioration of photosynthetic downregulation under increasing CO2 conditions.•While elevated CO2 promoted growth of both wild type and aps1 (accompanied by an increased net rate of CO2 fixation), it had no effect on gwd plants (where no significant effect was observed).•Under long day conditions, starch is an important determinant of the ability of Arabidopsis to sustain increased net photosynthesis and growth in response to elevated CO2.•These data also support the hypothesis that accelerated senescence and hindrance of CO2 diffusion to the stroma is caused by accumulation of large starch granules. Previous studies on Arabidopsis under long-term exposure to elevated CO2 have been conducted using starch synthesis and breakdown mutants cultured under short day conditions. These studies showed that starch synthesis can ameliorate the photosynthetic reduction caused by soluble sugar-mediated feedback regulation. In this work we characterized the effect of long-term exposure to elevated CO2 (800 ppm) on growth, photosynthesis and content of primary photosynthates in long-day grown wild type plants as well as the near starch-less (aps1) and the starch-excess (gwd) mutants. Notably, elevated CO2 promoted growth of both wild type and aps1 plants but had no effect on gwd plants. Growth promotion by elevated CO2 was accompanied by an increased net photosynthesis in WT and aps1 plants. However, the plants with the highest starch content (wild type at elevated CO2, gwd at ambient CO2, and gwd at elevated CO2) were the ones that suffered decreased in in vivo maximum carboxylation rate of Rubisco, and therefore, photosynthetic down-regulation. Further, the photosynthetic rates of wild type at elevated CO2 and gwd at elevated CO2 were acclimated to elevated CO2. Notably, elevated CO2 promoted the accumulation of stress-responsive and senescence-associated amino acid markers in gwd plants. The results presented in this work provide evidence that under long-day conditions, temporary storage of overflow photosynthate as starch negatively affect Rubisco performance. These data are consistent with earlier hypothesis that photosynthetic acclimation can be caused by accelerated senescence and hindrance of CO2 diffusion to the stroma due to accumulation of large starch granules.
ISSN:0098-8472
1873-7307
DOI:10.1016/j.envexpbot.2018.06.029