A sperm-activating peptide controls a cGMP-signaling pathway in starfish sperm.

Peptides released from eggs of marine invertebrates play a central role in fertilization. About 80 different peptides from various phyla have been isolated, however, with one exception, their respective receptors on the sperm surface have not been unequivocally identified and the pertinent signaling pathways remain ill defined. Using rapid mixing techniques and novel membrane-permeable caged compounds of cyclic nucleotides, we show that the sperm-activating peptide asterosap evokes a fast and transient increase of the cGMP concentration in sperm of the starfish Asterias amurensis, followed by a transient cGMP-stimulated increase in the Ca(2+) concentration.

AtKC1, a silent Arabidopsis potassium channel alpha -subunit modulates root hair K+ influx.

Ion channels in roots allow the plant to gain access to nutrients. The composition of the individual ion channels and the functional contribution of different alpha-subunits is largely unknown. Focusing on K(+)-selective ion channels, we have characterized AtKC1, a new alpha-subunit from the Arabidopsis shaker-like ion channel family.

KCO1 is a component of the slow-vacuolar (SV) ion channel.

The Arabidopsis double pore K+ channel KCO1 was fused to green fluorescent protein and expressed in tobacco protoplasts. Microscopic analysis revealed a bright green fluorescence at the vacuolar membrane. RT-PCR experiments showed that KCO1 is expressed in the mesophyll.