Figure 6.

Pathways of abscisic acid synthesis, transport, and signaling.

Notes: (A) Enzymes and intermediate products of the plastidial, endoplasmatic, and cytosolic pathways for abscisic acid production unify to the plastidal production of zeaxanthin (blue) as precursor for abscisic acid (red) synthesis in the cytosol. The storage pathway is catalyzed by BG1 and BG2 as well as by members of the UGT71B gene family. For further details, see text. The arrows are colored according to the species in which the enzymes were found (Fig. 1A). The expression of the identified genes in tomato is shown as explained in Figure 2. Genes coding for enzyme activities not expressed by any orthologue are indicated in gray. (B) Survey and localization of main transporters involved in uptake and intracellular distribution of abscisic acid. (C) The components involved in abscisic acid signaling are represented as interaction scheme.

Abbreviations: Proteins: ABA, ABA deficient; VDE1, violaxanthin de-epoxidase; NCED, nine-cis-epoxycarotenoid dioxygenase; CYP707A, cytochrome P450, family 707, subfamily A; UGT71B, UDP-glucosyl transferase 71B; BG, beta-1,3-glucanase; ABCG, ATP-binding casette G25; DTX, detoxification efflux carrier; ABCG, ATP-binding cassette G; AIT, ABA-importing transporter; ABCC1, ATP-binding cassette C; GTG, GPCR-type G protein; GCR, G protein coupled receptor; GPA, G PROTEIN alpha subunit; CCH, conditional chlorina; WRKY, WRKY DNA-binding protein; PYL1, PYR1-like 1, PYR, pyrabactin resistance; RCAR, regulatory component of ABA receptor; SNRK, sucrose nonfermenting 1(SNF1)-related protein kinase; ABI, ABA insensitive; ABF, abscisic acid responsive elements-binding factor.