Ectopic expression of the K+ channel β subunits from Puccinellia tenuiflora (KPutB1) and rice (KOB1) alters K+ homeostasis of yeast and Arabidopsis.
In this study, we cloned a cDNA for the K+ channel β subunit from the halophyte Puccinellia tenuiflora and named it KPutB1. KPutB1 was preferentially expressed in the roots and was transiently induced by K+-starvation, salt stress, or the combination of both stresses. By yeast two-hybrid assay, we demonstrated that KPutB1 interacts with PutAKT1, α subunit of an AKT1-type K+ channel of P. tenuiflora. The functional relevance of this interaction on K+-nutrition was investigated by co-expression experiments in yeast under various ionic conditions, and K+ channel α and β subunit homologues from rice (OsAKT1 and KOB1, respectively) were included for comparison. Yeast co-expressing PutAKT1 and the β subunits (KPutB1 and KOB1) had better growth and higher K+-uptake ability than yeast expressing PutAKT1 alone. In contrast, yeast co-expressing the β subunits (KPutB1 and KOB1) with OsAKT1 had slower growth and lower K+ uptake than yeast expressing OsAKT1 alone. Arabidopsis plants over-expressing the K+ channel β subunit of P. tenuiflora or rice showed increased shoot K+ content and decreased root Na+ content under control, 75 mM NaCl, and K+-starvation stress conditions. These results suggest that ectopic expression of the K+ channel β subunit could alter K+ and Na+ homeostasis in plants.
Asian Natural Environmental Science Center (ANESC), The University of Tokyo, 1-1-1 Midori-cho, Nishitokyo-shi, Tokyo 188-0002, Japan.
Sintho Wahyuning
SW
Ardie
Shunsaku
S
Nishiuchi
Shenkui
S
Liu
Tetsuo
T
Takano
D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism*; D012275:Oryza / Q000235:genetics*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D006109:Poaceae / Q000235:genetics*; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000235:genetics* / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015003:Yeasts / Q000235:genetics* / Q000378:metabolism*
D015221:Potassium Channels; D011188:Potassium