Functional PTB phosphate transporters are present in streptophyte algae and early diverging land plant
Résumé
Plants absorb inorganic phosphate (Pi) through Pi-transporters located in the plasma membrane of cells at the interface between the plant and the external environment. PHOSPHATE TRANSPORTER 1 (PHT1) proteins are H+/Pi-symporter responsible for Pi-uptake from the environment in angiosperms. PHT1 sequences are present in early diverging land plant and streptophyte algae suggesting that PHT1 proteins function in these taxa. However, Pi-uptake requires sodium (Na+)- influx in streptophyte algae suggesting that Na+/Pi-symporters are involved in Pi-uptake in some streptophytes. In chlorophytes algae, PHOSPHATE TRANSPORTER B (PTB) proteins have been hypothesised to be Na+/Pi-symporters responsible for Pi-uptake. Our work shows that PTB transporters are present in streptophytes. The higher steady state levels of mRNAs of most PTB genes of the early diverging land plant M. polymorpha and streptophyte algae C. nitellarum in low-Pi than in replete-Pi growth conditions support the role of streptophyte PTB proteins in Pi-uptake. Expression of three PTB proteins of the early diverging land plant M. polymorpha in the Saccharomyces cerevisiae pho2 mutant, defective in high-affinity Pi-transport, rescues growth in low-Pi environments confirming their Pi-transport function. These data suggests that two Pi- transport mechanisms – mediated by PTB and PHT1 proteins – operate in parallel in streptophyte algae and early diverging land plants.
Domaines
Sciences du Vivant [q-bio]
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