Diurnal and Circadian Regulation of Putative Potassium Channels in a Leaf Moving Organ

M. Moshelion
2002 Plant Physiology  
In a search for potassium channels involved in light-and clock-regulated leaf movements, we cloned four putative K channel genes from the leaf-moving organs, pulvini, of the legume Samanea saman. The S. saman SPOCK1 is homologous to KCO1, an Arabidopsis two-pore-domain K channel, the S. saman SPORK1 is similar to SKOR and GORK, Arabidopsis outwardrectifying Shaker-like K channels, and the S. saman SPICK1 and SPICK2 are homologous to AKT2, a weakly-inward-rectifying Shaker-like Arabidopsis K
more » ... nel. All four S. saman sequences possess the universal K-channel-specific pore signature, TXXTXGYG, strongly suggesting a role in transmembrane K ϩ transport. The four S. saman genes had different expression patterns within four leaf parts: 'extensor' and 'flexor' (the motor tissues), the leaf blades (mainly mesophyll), and the vascular bundle ('rachis'). Based on northern blot analysis, their transcript level was correlated with the rhythmic leaf movements: (a) all four genes were regulated diurnally (Spick2, Spork1, and Spock1 in extensor and flexor, Spick1 in extensor and rachis); (b) Spork1 and Spock1 rhythms were inverted upon the inversion of the day-night cycle; and (c) in extensor and/or flexor, the expression of Spork1, Spick1, and Spick2 was also under a circadian control. These findings parallel the circadian rhythm shown to govern the resting membrane K ϩ permeability in extensor and flexor protoplasts and the susceptibility of this permeability to light stimulation (Kim et al., 1993) . Thus, Samanea pulvinar motor cells are the first described system combining light and circadian regulation of K channels at the level of transcript and membrane transport. fax 972-8-946 -7763. Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/
doi:10.1104/pp.128.2.634 pmid:11842166 fatcat:2ylisvss35hcjfti2kodq634rq