RT–PCR, was significantly higher for Willowleaf than
Eureka lemon. However, several upstream genes, particularly
CitDxs, were down regulated in the somatic hybrid,
indicating a level of partial dominance of lemon in that part
of the pathway. Additionally, CitZep and Cit Nceds, critical
enzymatic steps leading to ABA synthesis from
carotenoid substrates, were expressed at levels in the
hybrid that exceeded both donor parents. The combination
of lower levels of upstream gene expression with the
greater downstream consumption of carotenoids, leading to
increased ABA levels and supported by increased gene
expression, could explain the comparative phenotypic
observations of the hybrid with the donors.