Nutrient cycling is an important mechanism for homeostasis in plant cells

Abstract

Homeostasis in living cells refers to the steady state of internal, physical, and chemical conditions. It is maintained by self-regulation of the dynamic cellular system. In order to gain insight into homeostatic mechanisms that keep cytosolic nutrient concentrations in plant cells within a homeostatic range, I performed computational cell biology experiments. Systems of membrane transporters were modelled mathematically followed by the simulation of their dynamics. The detailed analyses of what-if scenarios demonstrate that a single transporter type for a nutrient, irrespective whether it is a channel or a co-transporter, is not sufficient to set a desired cytosolic concentration. A cell cannot flexibly react on different external conditions. At least two different transporter types for the same nutrient are required, which are energized differently. The gain of flexibility in adjusting the nutrient concentration was accompanied by the establishment of energy-consuming nutrient cycles at the membrane suggesting that these sometimes called futile cycles are not as futile as they appear. This understanding may help in future to design new strategies for increasing nutrient use efficiency of crop plants taking into account the complex interplay of transporter networks at the cellular level. One sentence summaryFirst principles of membrane transport explain why the maintenance of a constant cytosolic nutrient concentration is often accompanied by the futile cycling of the nutrient across the membrane.