An Arabidopsis thaliana Gene with Sequence Similarity to the S-Locus Receptor Kinase of Brassica oleracea : Sequence and Expression

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Abstract
Primary signal transduction plays a vital role in the way plants react to environmental and developmental signals. We report the sequence and expression of a putative receptor kinase gene, ARK1, in Arabidopsis thaliana that may be important in this regard. This Arabidopsis gene encodes a transmembrane protein with a cytoplasmic kinase catalytic domain, a transmembrane region, and an extracellular domain with sequence similarity to the secreted S-locus glycoprotein (SLG) gene of Brassica oleracea. This structure is similar to the S-locus receptor kinase (SRK) gene of Brassica and to the receptor kinase ZmPK1 gene of maize. RNA blots indicate that transcripts accumulate predominantly in leaf tissue, with limited amounts in stem and floral bud tissue and no detectable transcripts accumulating in root tissue. A smaller transcript that could be an alternative transcript of ARK1 also accumulates in leaf tissue. This transcript possibly encodes a secreted SLG-like glycoprotein that lacks transmembrane and kinase domains. The predominantly vegetative expression of ARK1 indicates that this gene is not primarily involved in pollen/pistil interactions in Arabidopsis.