ABA is a positive regulator of dormancy in many species
(Kucera et al. 2005). The involvement of ABA metabolism
in dormancy regulation of a phylogenetically broad range
of species was already evident from early studies on rosids
(Koornneef et al. 1982), asterids (Groot & Karssen 1992)
and monocots (Tan et al. 1997) where mutations of ABA
biosynthesis genes showed reduced dormancy of freshly
harvested seeds. These initial findings were further supported
by studies in a broad range of species as depicted
below. Especially, the 9-cis-epoxycarotenoid dioxygenase
(NCED) genes involved in ABA biosynthesis and the
ABA-8′-hydroxylase (CYP707A) genes involved in ABA
degradation seem to have universal roles (Nambara et al.
2010