Abstract
The GCAs are new tetraploid interspecific low-caffeine hybrids bred in Madagascar. They are produced from Coffea. eugenioides, C. canephora and C. arabica. Our previous studies indicate that C. eugenioides has the capacity to rapidly degrade caffeine in addition to the low biosynthetic activity. In order to clarify the mechanism of low caffeine accumulation in the GCAs, we examined the overall metabolism of [8-14C]adenosine in young leaves and immature fruits of the GCAs, C. eugenioides, C. canephora and C. arabica. Although little differences were found in the formation of nucleotides and RNA between four species used, the biosynthetic activity of purine alkaloids was 50-90% reduced in GCA. Instead, increase in the conventional purine catabolic activity initiated from IMP was observed. Catabolism of [8-14C]caffeine was negligible at least during 18 hours in GCAs. Low caffeine accumulation in the GCA plants seems to be due to lowered caffeine biosynthesis at the N-methyltransferase reactions.
