| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2000: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1999: ¥2,700,000 (Direct Cost: ¥2,700,000)
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| Research Abstract |
In order to investigate the difference of ripening characteristics between melon and cucumber fruits, analyses were conducted on regulation of ACC synthase (ACS) gene expression and on expression of ethylene receptor genes during fruit ripening.
1. ACS genes from melon and cucumber fruits were highly homologous in terms of gene structure and sequence, not only at the cDNA but also at the genomic levels. Analysis of cis-element revealed that many common elements were present in the promoters of both ACS genes. Southern blot analysis indicated that each ACS gene was present as a single copy per haploid genome.
2. Promoter activities of ACS genes from melon and cucumber were measured transiently using β- glucuronidase (GUS) as a reporter gene. Promoter (ca. 2kb) of a cucumber ACS gene, CS-ACS1, showed its activity in mesocarp disks of ripe melon fruit. In addition, there was no difference in promoter (ca. 2kb) activities between melon ACS1 gene (CMe-ACS1) and CS-ACS1 in immature and mature melon and cucumber mesocarp disks by the GUS transient assay.
3. Southern analysis was conducted on ethylene receptor genes from melon and cucumber. Ethylene receptor genes, ETR1 and ERS1, were present in melon and cucumber as a single copy per haploid genome, and both genes were well conserved beyond the cultivars. Northern blotting demonstrated that expression of ETR1and ERS1 genes were ethylene-dependent in cucumber fruit, which coincided well with the already reported expression pattern of these genes in melon fruit.
As a conclusion, it was presumed that the difference between melon and cucumber fruits in ripening characteristics was caused in each fruit during ripening between the steps of ethylene receptor and ACS1 gene transcription in ethylene signal transduction pathway.
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