棉 花 学 报 Cotton Science 2006，18(6)：379-385
Advances in Research of Molecular Mechnisms of Potassium Uptaking and Transportation in Plants Abstract：Potassium plays a key role in the activity and development of plants. Potassium transportation in plants can be divided into two parts，high affinity and low affinity. At the molecular level，genes of KUP/HAK/KT and HKT families are essential for high affinity absorbtion， while K+ channel of Shaker and KCO families are responsible for low affinity activity. KAT1 and AKT1 are the first K+ channel genes cloned in plant，while HKT1 is the first K+ carrier gene cloned in wheat. K+ is also essential for the development of cotton (Gossypium hirsutum).The potassium transporter GhKT1 in cotton is critical for the process of cotton fiber elongation. In general，K+ channels function in millimol K+ concentration. However，AtAKT1，a member of Shaker family，can take its role in a wide range of external K+ concentrations，from micro-mole to milli-mole. Several independent experiments related to AtAKT1 knockout supported that AtAKT1 palyed a key role in Arabidopsis K+ nutrition. The cloning and functional analysis of AtAKT1 homologe genes such as，SKT1， LKT1，MKT1，TaAKT1 and OsAKT1，indicated that AKT1 was essential for potassium uptaking and transportation in plant. In recent studies，the investigation of the changes of transcriptional level in response to the external K+ availability was largely used as a method to identify the functions of both K+ channels and transporters. AtAKT1 could be activated by K+ shortage，however，no transcriptional levels have been detected either using Northern Blot Analysis or Micro-array，roviding that the regulations of AtAKT1 occur at post-transcriptional level. AtKC1，a member of Shaker family ，could not function as a channel protein alone，but could physically interact with AtAKT1.In response to K+ deficency，AtKC1 could be temporally activated. Therefore，it was believed that the regulation of AtAKT1 was largely through the modulation of AtKC1 . In Arabidopsis，genes from KUP/HAK/KT family did not likely answer low potassium stress at transcriptional level except AtHAK5，which was strongly induced by K+ deficiency. During this process，NH4+ might play some roles in the signaling of plant K+ status. Members from HKT family facilitated Na+/Na+ or K+ /Na+ symport. Therefore，these transporters might take some roles in Na+ uptake and recirculation. The comlicated molecular mechanisms of K+ uptake and transportation enabled plant to survive in the changing environment.
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