SLG/SRK-like genes are expressed in the reproductive tissues of Ipomoea trifida

Abstract

Self-incompatibility of Ipomoea trifida is under the control of a single multi-allelic locus, called the S-locus, and is genetically the same as the sporophytic system found in some species of Brassica. We investigated whether the S-locus-specific glycoprotein (SLG) and S receptor kinase (SRK) genes associated with the self-incompatibility of Brassica are expressed in the reproductive tissues of I. trifida. We amplified mRNAs from reproductive tissues of I. trifida by reverse transcriptase PCR using primers corresponding to conserved regions of the Brassica SLGs. Four kinds of PCR fragments were amplified in this experiment. These fragments were designated IPG1 to IPG4 based on dot-blot cross-hybridization. Nucleotide sequencing of the clones revealed 40–46% similarity to the Brassica SLGs and SRKs at the protein level. Northern analysis using IPG1 as a probe revealed a major transcript of 2.8 kb that would correspond in size to a fully spliced SRK transcript of Brassica. The transcript for IPG1 was detected in both mature stigma and anther tissue and was developmentally regulated. The experimental results reported here indicate that at least four kinds of SLG/SRK-like genes are expressed in the reproductive tissues of Ipomoea.