Arabidopsis plants perform arithmetic division to prevent starvation at night

TL;DR

Arabidopsis plants perform an arithmetic division to regulate starch degradation at night, ensuring reserves last until dawn by adjusting the rate based on starch content and expected night length.

Contribution

The paper introduces two novel chemical kinetic models that implement analog arithmetic division, explaining how plants dynamically regulate starch degradation.

Findings

Models successfully predict plant responses to altered night conditions.

Mutations in starch pathways affect the division-based regulation.

Components of starch degradation are linked to the division mechanism.

Abstract

Photosynthetic starch reserves that accumulate in Arabidopsis leaves during the day decrease approximately linearly with time at night to support metabolism and growth. We find that the rate of decrease is adjusted to accommodate variation in the time of onset of darkness and starch content, such that reserves last almost precisely until dawn. Generation of these dynamics therefore requires an arithmetic division computation between the starch content and expected time to dawn. We introduce two novel chemical kinetic models capable of implementing analog arithmetic division. Predictions from the models are successfully tested in plants perturbed by a night-time light period or by mutations in starch degradation pathways. Our experiments indicate which components of the starch degradation apparatus may be important for appropriate arithmetic division. Our results are potentially relevant for any biological system dependent on a food reserve for survival over a predictable time period.