The ionic environment controls the contribution of the barley HvHAK1 transporter to potassium acquisition.
The control of potassium (K+) acquisition is a critical requirement for plant growth. Although HAK1 (high affinity K+ 1) transporters provide a pathway for K+ acquisition, the effect exerted by the ionic environment on their contribution to K+ capture remains essentially unknown. Here, the influence of the ionic environment on the accumulation of transcripts coding for the barley (Hordeum vulgare) HvHAK1 transporter as well as on HvHAK1-mediated K+ capture has been examined. In situ mRNA hybridization studies show that HvHAK1 expression occurs in most root cells, being augmented at the outermost cell layers. Accumulation of HvHAK1 transcripts is enhanced by K+ deprivation and transiently by exposure to high salt concentrations. In addition, studies on the accumulation of transcripts coding for HvHAK1 and its close homolog HvHAK1b revealed the presence of two K+-responsive pathways, one repressed and the other insensitive to ammonium. Experiments with Arabidopsis (Arabidopsis thaliana) HvHAK1-expressing transgenic plants showed that K+ deprivation enhances the capture of K+ mediated by HvHAK1. A detailed study with HvHAK1-expressing Saccharomyces cerevisiae cells also revealed an increase of K+ uptake after K+ starvation. This increase did not occur in cells grown at high Na+ concentrations but took place for cells grown in the presence of NH4+. 3,3'-Dihexyloxacarbocyanine iodide accumulation measurements indicate that the increased capture of K+ in HvHAK1-expressing yeast cells cannot be explained only by changes in the membrane potential. It is shown that the yeast protein phosphatase PPZ1 as well as the halotolerance HAL4/HAL5 kinases negatively regulate the HvHAK1-mediated K+ transport.
Fulgenzi
Fabiana R
FR
Instituto de Investigaciones Biotecnológicas, Universidad Nacional de San Martín-Consejo Nacional de Investigaciones Científicas y Técnicas, Instituto de Tecnología Industrial, San Martín 1650, Provincia de Buenos Aires, Argentina.
Peralta
María Luisa
ML
Mangano
Silvina
S
Danna
Cristian H
CH
Vallejo
Augusto J
AJ
Puigdomenech
Pere
P
Santa-María
Guillermo E
GE
D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D004777:Environment; D018506:Gene Expression Regulation, Plant; D001467:Hordeum / Q000235:genetics / Q000378:metabolism*; D007477:Ions; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000378:metabolism; D011188:Potassium / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D020239:Receptor Cross-Talk; D012413:Rubidium / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D012965:Sodium Chloride / Q000378:metabolism; D015854:Up-Regulation
D027682:Cation Transport Proteins; C110543:HAK1 protein, plant; D007477:Ions; D010940:Plant Proteins; D000644:Quaternary Ammonium Compounds; D029701:Saccharomyces cerevisiae Proteins; D012965:Sodium Chloride; D012964:Sodium; D011494:Protein Kinases; C522341:Hal5 protein, S cerevisiae; C075119:PPZ1 protein, S cerevisiae; D010749:Phosphoprotein Phosphatases; D012413:Rubidium; D011188:Potassium