Leaf starch reserves keep stomata on time
Image credit for featured image: Gilles Pantin
Westgeest et al. use a high-throughput phenotyping pipeline to explore the connection between leaf starch and stomatal opening
https://doi.org/10.1093/plcell/koad158
Adrianus J. Westgeest and Florent Pantin, L’Institut Agro, Montpellier, France
Background: Leaves have tiny pores called stomata, which are surrounded by a pair of guard cells. Stomata generally open during the day to facilitate the capture of CO2 for photosynthesis, and close at night to limit the loss of water vapor. One century ago, pioneering observations under the microscope revealed that stomata preopen several hours before dawn. We know now that the circadian clock, the plant’s endogenous timer, is necessary for stomata to preopen at night. In addition to the circadian clock, leaf starch is synthesized during the day and broken down at night to generate sugars for energy, thus acting as a transitory metabolic clock.
Question: Production of sugars from starch in guard cells was recently found to be essential for light-induced stomatal opening. How does leaf starch metabolism connect with endogenous stomatal movements such as nighttime preopening?
Findings: We developed PhenoLeaks, a phenotyping pipeline to analyze the transpiration dynamics over days and nights on 150 plants at the same time. We screened a collection of Arabidopsis starch mutants and found that severe mutations in starch metabolism not only disrupt stomatal preopening at night, but also delay endogenous stomatal movements during the whole day. When the lesions in starch metabolism were confined to the guard cells, stomata showed normal endogenous movements, suggesting that starch from the rest of the leaf is able to set the tempo of stomatal movements, most likely by providing sugars that interact with the guard-cell circadian clock.
Next steps: The challenge now is to decipher the molecular dialogue between the guard cells and the rest of the leaf, and to exploit the endogenous stomatal movements to improve water use efficiency in crop species.
Reference:
Adrianus J. Westgeest, Myriam Dauzat, Thierry Simonneau, Florent Pantin (2023) Leaf starch metabolism sets the phase of stomatal rhythm. https://doi.org/10.1093/plcell/koad158
