Plant KT/KUP/HAK potassium transporters: single family - multiple functions

Abstract

Background and aims: Potassium transporters belonging to the KT/KUP/HAK family are important for various aspects of plant life including mineral nutrition and the regulation of development. Genes encoding these transporters are present in the genomes of all plants, but have not been found in the genomes of Protista or Animalia. The aim of this Botanical Briefing is to analyse the function of KT/KUP/HAK transporters from evolutionary, molecular and physiological perspectives.

Scope: This Briefing covers the phylogeny and evolution of KT/KUP/HAK transporters, the role of transporters in plant mineral nutrition and potassium homeostasis, and the role of KT/KUP/HAK transporters in plant development.

Fig. 1.

Genomic distribution of KT/KUP/HAK transporters. KT/KUP/HAK transporter genes are present in all plant genomes studied so far (see text for details), but were not found in Protista and Animalia. The presence of these transporters in Amoebozoa requires further confirmation. The evolutionary tree is adapted from Pennisi (2003).

Fig. 2.

KT/KUP/HAK transporter genes in plant genomes. Data were obtained through the mining of TIGR and JGI genomic databases. The evolutionary tree is adapted from Pennisi (2003).

Fig. 3.

Auxin fluxes in the root-tip of wild-type (WT) and trh1 plants. The trh1 mutation partially blocks auxin transport through the root-cap. This blockage causes a reduction in overall acropetal auxin transport through the stele and decreases in the auxin concentration in the cortex and epidermis. Defects in root-hair development and gravitropic behaviour in the trh1 mutant are due to sub-optimal concentrations of auxin in the epidermis. Reproduced from Vicente-Agullo et al. (2004) with permission.