Abstract
Germination of lettuce (Lactuca sativa L. cv. Grand Rapids) seeds is regulated by phytochrome. Endogenous levels of physiologically active gibberellin (GA), (GA)_1,increased and those of abscisic acid (ABA) decreased after red-light irradiation during germination of lettuce seeds. These changes of the two phytohormone levels might be important for induction of germination by light. In this research, we isolated cDNAs encoding 9-cis-epoxycarotenoid dioxygenases (NCEDs), an ABA biosynthetic enzyme, and analyzed these expression patterns during germination by quantitative RT-PCR in order to investigate the mechanism on decrease of endogenous ABA levels. Four cDNAs, LsNCED1,2,3,4 were isolated from the extracts of lettuce seeds and seedlings. The expression levels of LsNCED2,4 decreased by red-light irradiation, which might be involved in the decline of the ABA levels.
