The transport of carboxylic acids and important role of Jen1p transporter during the development of yeast colonies
Abstract
On solid substrates, yeast colonies pass through distinct developmental phases characterized by changes in pH of their surroundings from acidic to nearly alkaline and vice versa. At the beginning of the alkali phase colonies start to produce ammonia, which functions as a quorum sensing molecule inducing the reprogramming of cell metabolism.
Such reprogramming includes among others the activation of several plasma membrane transporters and is connected with colony differentiation. In this study, we show that colony cells can use two transport mechanisms to import lactic acid: a "saturable" component of the transport, which requires the presence of functional Jen1p transporter and a "non-saturable" component (diffusion) that is independent of Jen1p.
During colony development, the efficiency of both transport components changes similarly in central and outer colonial cells. While the lactate uptake capacity of central cells gradually decreases during colony development, the lactate uptake capacity of outer cells peaks during the alkali phase and is also kept relatively high in the 2nd acidic phase.
This lactate uptake profile correlates with the localisation of the Jen1p transporter to the plasma membrane of colony cells. Both lactic acid uptake mechanisms are diminished in sok2 colonies where JEN1 expression is decreased.
The Sok2p transcription factor may therefore be involved in the regulation of the non-saturable lactic acid uptake in yeast colonies.