Abstract
Stomatal opening, which controls gas exchanges between plants and the atmosphere, results from an increase in turgor of the two guard cells that surround the pore of the stoma. KAT1 was the only inward K(+) channel shown to be expressed in Arabidopsis guard cells, where it was proposed to mediate a K(+) influx that enables stomatal opening. We report that another Arabidopsis K(+) channel, KAT2, is expressed in guard cells. More than KAT1, KAT2 displays functional features resembling those of native inward K(+) channels in guard cells. Coexpression in Xenopus oocytes and two-hybrid experiments indicated that KAT1 and KAT2 can form heteromultimeric channels. The data indicate that KAT2 plays a crucial role in the stomatal opening machinery.
Highlights
The epidermis of the aerial organs of plants presents a waxy cuticle that prevents water loss, but impedes direct access of the photosynthesizing tissues to atmospheric CO2
We report that another Arabidopsis K؉ channel, KAT2, is expressed in guard cells
Within the Arabidopsis Shaker-like family, the strongest similarities are found to KAT1
Summary
KAT2 cDNA Cloning—The 5Ј-region of KAT2 cDNA (see Fig. 1C; GenBankTM/EBI accession number AJ288900) was determined by RACE-PCR on poly(A)ϩ mRNA isolated from 14-day-old plantlet leaves. Amplified fragments corresponding to the 5Ј-end of KAT2 cDNA were cloned and sequenced. The full-length KAT2 open reading frame was isolated by reverse transcription-PCR on poly(A)ϩ mRNA using a primer hybridizing at the ATG codon and containing a SpeI site (5ЈACTAGTATGTTGAAGAGAAAGCACCTCAACAC-3Ј) and a reverse primer hybridizing at the stop codon and containing a NotI site (5Ј-GCGGCCGCTTAAGAGTTTTCATTGATGAGAATATACAAATG-3Ј). The amplified fragment (2.1 kilobases) was cloned at the EcoRV site of
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