Molecular characterization of the Arabidopsis 9‐cis epoxycarotenoid dioxygenase gene family

Abstract

These authors contributed equally to this work. SummaryA key regulated step in abscisic acid (ABA) biosynthesis in plants is catalyzed by 9-cis epoxycarotenoid dioxygenase (NCED), which cleaves 9-cis xanthophylls to xanthoxin, a precursor of ABA. In Arabidopsis, ABA biosynthesis is controlled by a small family of NCED genes. Nine carotenoid cleavage dioxygenase (CCD) genes have been identi®ed in the complete genome sequence. Of these, ®ve AtNCEDs (2, 3, 5, 6, and 9) have been cloned and studied for expression and subcellular localization. Although all ®ve AtNCEDs are targeted to plastids, they differ in binding activity of the thylakoid membrane. AtNCED2, AtNCED3, and AtNCED6 are found in both stroma and thylakoid membrane-bound compartments. AtNCED5 is exclusively bound to thylakoids, whereas AtNCED9 remains soluble in stroma. A quantitative real-time PCR analysis and histochemical staining of promoter::GUS activity in transgenic Arabidopsis revealed a complex pattern of localized NCED expression in well-watered plants during development. AtNCED2 and AtNCED3 account for the NCED activity in roots, with localized expression in root tips, pericycle, and cortex cells at the base of lateral roots. Localized AtNCED2 and AtNCED3 expression in pericycle cells is an early marker of lateral initiation sites. AtNCED5, AtNCED6, AtNCED3, and AtNCED2 are expressed in¯owers with very high AtN-CED6::GUS activity occurring in pollen. AtNCED5::GUS, and to lesser degrees, AtNCED2::GUS and AtN-CED3::GUS are expressed in developing anthers. AtNCED5, AtNCED6, AtNCED9, and AtNCED3 contribute to expression in developing seeds with high levels of AtNCED6 present at an early stage. GUS analysis indicates that AtNCED3 expression is con®ned to the base of the seed, whereas AtNCED5 and AtNCED6 are expressed throughout the seed. Consistent with the studies conducted by Iuchi and his colleagues in 2001, AtNCED3 is the major stress-induced NCED in leaves. Our results indicate that developmental control of ABA synthesis involves localized patterns of AtNCED gene expression. In addition, differential membrane-binding capacity of AtNCEDs is a potential means of post-translational regulation of NCED activity.

The multifaceted role of ABA in disease resistance

“…ABA in the form of its inactive glucose ester conjugate is highly mobile throughout the plant and is released into its active form when it has reached the target tissue. Localization studies of ABA biosynthetic enzymes indicate that the vascular bundles are the active sites of ABA synthesis in turgid, non-stressed plants [58,59]. Therefore, all vascular plant tissues have the capacity to synthesize ABA.…”

Abscisic acid levels in tomato ovaries are regulated by LeNCED1 and SlCYP707A1

“…In other species, such as Arabidopsis and rice, NCED enzymes are encoded by small gene families composed of Wve and three members, respectively (Tan et al 2003). However, in tomato Fig.…”

“…2 shows that the four tomato sequences most similar to LeNCED1 did not group together with the LeNCED1 and the other functional NCED genes from Arabidopsis, rice, potato and maize. Three of the four tomato sequences (TC175556, TC154638, and TC154637) formed a separate group, while the other sequence (TC156234) grouped together with other carotenoid cleavage dioxygenases (CCDs) that are not known to be related to ABA biosynthesis (Tan et al 2003). In addition, the deduced amino acid sequences of the four tomato sequences were less than 35% identical to the functional Arabidopsis or tomato NCED amino acid sequences.…”

Cloning and characterisation of a maize carotenoid cleavage dioxygenase (ZmCCD1) and its involvement in the biosynthesis of apocarotenoids with various roles in mutualistic and parasitic interactions

“…Based on the sequence homology to Vp14, nine CCDs have been identiWed in the Arabidopsis thaliana genome. Among them, Wve are Vp14-like (NCED2,NCED3,NCED5,NCED6 and NCED9) and are supposed to be involved in ABA biosynthesis (Tan et al 2003). The other four have been given the generic designation carotenoid cleavage dioxygenase (CCD1, CCD4, CCD7 and CCD8) (Auldridge et al 2006a).…”