Has a 11,12(11',12') 9-cis epoxycarotenoid cleavage activity. Catalyzes the first step of abscisic-acid (ABA) biosynthesis from carotenoids. Required for ABA accumulation upon drought (Ref.2). Required for ABA-mediated regulation of anther/pollen development, including metabolism, cell wall modification and transcription level (PubMed:29632966). Positive regulator of fruit ripening involved in the biosynthesis of abscisic acid (ABA); initiates ABA biosynthesis at the onset of fruit ripening (PubMed:19246595, PubMed:22108525, PubMed:25039074). Modulates the degree of pigmentation and carotenoid composition as well as pectin catabolism during ripening and may regulate the ethylene production and action in climacteric tomato fruit (PubMed:22345638, PubMed:22108525). a 9-cis-epoxycarotenoid + O2 = 2-cis,4-trans-xanthoxin + a 12'-apo-carotenal 9-cis-violaxanthin + O2 = (3S,5R,6S)-5,6-epoxy-3-hydroxy-5,6-dihydro-12'-apo-beta-caroten-12'-al + 2-cis,4-trans-xanthoxin 9'-cis-neoxanthin + O2 = (3S,5R,6R)-3,5-dihydroxy-6,7-didehydro-5,6-dihydro-12'-apo-beta-caroten-12'-al + 2-cis,4-trans-xanthoxin Binds 1 Fe(2+) ion per subunit. Plant hormone biosynthesis; abscisate biosynthesis. Partially bound to the thylakoid. Expressed in developing and ripening fruits (PubMed:22345638, PubMed:22108525). Highly expressed in pulp (PubMed:25039074). Observed in unpollinated ovaries (e.g. ovules, placenta and pericarp) (PubMed:19322584). Expressed in flowers (PubMed:29632966). Expressed in the meristem during gametogenesis and mainly in ovule, stigma, anther/pollen and vascular tissues during flower development. In flower buds, present in petal primordium and apical meristem. Later expressed in stamen primordium and pistil meristem after petal formation. Accumulates in stamen, pistil and vascular tissues of the bud base. Highly expressed in sporogenous cells in anther, pistil stigma, ovules, pollen grains, anther walls, and basal vascular bundle. In anthers, first present at low levels, then increases rapidly to reach a peak at stages 13-14 (when microspores transform into vacuolated pollen grains after mitotic divisions) before declines gradually (PubMed:29632966). In fruits, levels decline from the immature stage to the mature green stage and then rapidly increase to a peak at the turning stage (PubMed:22345638, PubMed:22108525, PubMed:25039074). Highly expressed in fruits at the onset of ripening when the abscisic-acid (ABA) content becomes high (PubMed:19246595, PubMed:22345638, PubMed:22108525). Progressive level reduction in ovaries (e.g. ovules, placenta and pericarp) after pollination (PubMed:19322584). Induced by drought (Ref.1, Ref.2, PubMed:25039074). Accumulates in dehydration-treated fruits (PubMed:19246595). Repressed after pollination. Inhibited by gibberellic acid (GA(3)) and auxin (4-Cl-IAA) treatments (PubMed:19322584). Induced by abscisic acid (ABA) (PubMed:19322584, PubMed:25039074). Up-regulated by salicylic acid (SA) in roots; this accumulation is repressed by salt stress (NaCl) with high SA treatment but with low SA (PubMed:25039074). Regulated by the NAC transcription factor NAP2 (PubMed:29760199). The mutant notabilis (not) is abscisic acid (ABA)-deficient (including in response to dehydration) and exhibits a reduced growth and lower ethylene levels (Ref.2). Abnormal development of anther/pollen leading to serious pollen deterioration (PubMed:29632966). Fruit-specific suppression leads to reduced ABA accumulation resulting in an increase in ethylene levels, by increasing the transcription of genes related to the synthesis of ethylene during ripening. Deep red fruits which accumulate higher levels of lycopene and beta-carotene probably due to the metabolism of 'backlogged' carbon as a result of disturbed ABA signaling (PubMed:22345638). When disrupted in fruits, altered expression of genes involved in ABA metabolism and signaling and disturbed expression of pectin catabolism family genes are observed (PubMed:22108525, PubMed:25039074). In addition, fruits are smaller, but in a slightly higher number, with a longer shelf life; they are firmer and more flexible during the ripening stages after the mature green stage with considerably fewer seeds, greater viscosity of juices, higher ethylene release and a deep red color (PubMed:22108525). Silenced plants fruits have a slow/suppressed ripening with abnormal orange color and associated with lower ABA levels. In fruits exposed to water deprivation, water loss of the sepal is enhanced (PubMed:25039074). Interfering with NCED1 expression in fruits increases shelf life and reduces seed number, but increases viscosity of juices and modifies fruit texture. Belongs to the carotenoid oxygenase family.