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FEBS Lett. 2018 Aug;592(16):2739-2759. doi: 10.1002/1873-3468.13198. Epub 2018 Aug 10.

Starch biosynthesis by AGPase, but not starch degradation by BAM1/3 and SEX1, is rate-limiting for CO2 -regulated stomatal movements under short-day conditions.

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Division of Biological Sciences, Cell and Developmental Biology Section, University of California San Diego, La Jolla, CA, USA.
Department of Plant & Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel.
The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.


Starch in guard cells functions in osmoregulation during stomatal movements. Starch metabolism is controlled by the circadian clock. We investigated the role of starch metabolism in stomatal responses to CO2 under different photoperiodic conditions. Guard cell starch levels correlate with low/high [CO2 ] exposure. Starch biosynthesis-deficient AGPase (ADG1) mutants but, unexpectedly, not the starch degradation-deficient BAM1, BAM3, and SEX1 mutants alone, are rate-limiting for stomatal conductance responses to [CO2 ]-shifts. Interestingly, AGPase is rate-limiting solely under short- but not long-day conditions. These findings suggest a model of enhanced AGPase activity in guard cells under short days such that starch biosynthesis becomes rate-limiting for CO2 -induced stomatal closing.


Arabidopsis ; gas exchange; guard cell; photoperiod; starch degradation; starch synthesis

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