Isolation and characterization of cDNA clones expressed under male sex expression conditions in a monoecious cucumber plant (Cucumis sativus L. cv. Winter Long)

In order to clone sex determination genes, both differential screening of a cDNA library and differential display reverse transcription PCR (DDRT-PCR) were conducted, using apex tissues from a Korean cucumber cultivar that exhibited different sex expression responses to differing photoperiods. Two genes (CsM1 and CsM2) expressed only under specific male expression conditions were then cloned via differential screening of a cDNA library and designated CsCYR (Cucumis sativus cyclin-related) and CsCYP (C. sativus cyclophilin). Both genes appear to be single-copy genes, and both express under male-expressing SD (short-day) conditions. CsM10 (C. sativus male specific clone 10) was isolated via DDRT-PCR, and was expressed preferentially under male expression conditions. The CsM10 gene encodes a non-coding RNA, and harbors a 179bp-conserved sequence, found in three genes which have been classified as a biotic stress signal-associated non-translatable RNA (or non-coding RNA) group. The CsM10 gene is also a single-copy gene, which is localized in the telomeric region of chromosome 6, and its expression is different in different tissues, developmental stages, and photoperiods. Based on the obtained sequence structures and expression patterns of CsM10 and its homologues, we suggest that CsM10 function appears to occur at the RNA level.