An alternative, zeaxanthin epoxidase-independent abscisic acid biosynthetic pathway in plants
Moreno, Juan C.
de Lera, Angel R.
KAUST DepartmentBiological and Environmental Science and Engineering (BESE) Division
Biological and Environmental Sciences and Engineering Division, Center for Desert Agriculture, The BioActives Lab, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia.
Center for Desert Agriculture
Computational Bioscience Research Center (CBRC)
Computer, Electrical and Mathematical Science and Engineering (CEMSE) Division
Online Publication Date2021-09-20
Print Publication Date2021-09
Embargo End Date2022-09-20
Permanent link to this recordhttp://hdl.handle.net/10754/672051
MetadataShow full item record
AbstractAbscisic acid (ABA) is an important carotenoid-derived phytohormone that plays essential roles in plant response to biotic and abiotic stresses as well as in various physiological and developmental processes. In Arabidopsis, ABA biosynthesis starts with the epoxidation of zeaxanthin by the ABA DEFICIENT 1 (ABA1) enzyme, leading to epoxycarotenoids, e.g., violaxanthin. The oxidative cleavage of 9-cis-epoxycarotenoids, a key regulatory step catalyzed by 9-CIS-EPOXYCAROTENOID DIOXYGENASE, forms xanthoxin that is converted in further reactions mediated by ABA DEFICIENT 2 (ABA2), ABA DEFICIENT 3 (ABA3), and ABSCISIC ALDEHYDE OXIDASE 3 (AAO3) into ABA. By combining genetic and biochemical approaches, we unravel here an ABA1-independent ABA biosynthetic pathway starting upstream of zeaxanthin. We identified the carotenoid cleavage products, i.e., apocarotenoids, β-apo-11-carotenal, 9-cis-β-apo-11-carotenal, 3-OH-β-apo-11-carotenal, and 9-cis-3-OH-β-apo-11-carotenal as intermediates of this ABA1-independent ABA biosynthetic pathway. Using labeled compounds, we showed that β-apo-11-carotenal, 9-cis-β-apo-11-carotenal, and 3-OH-β-apo-11-carotenal are successively converted into 9-cis-3-OH-β-apo-11-carotenal, xanthoxin, and finally into ABA in both Arabidopsis and rice. When applied to Arabidopsis, these β-apo-11-carotenoids exert ABA biological functions, such as maintaining seed dormancy and inducing the expression of ABA-responsive genes. Indeed, the transcriptomic analysis revealed a high overlap of differentially expressed genes regulated by β-apo-11-carotenoids and ABA, but also suggested that these compounds exert ABA-independent regulatory activities. Taken together, our study identifies a biological function for the common plant metabolites β-apo-11-carotenoids, extends our knowledge about ABA biosynthesis and provides new insights into plant apocarotenoid metabolic networks.
CitationJia, K.-P., Mi, J., Ali, S., Ohyanagi, H., Moreno, J. C., Ablazov, A., … Al-Babili, S. (2021). An alternative, zeaxanthin epoxidase-independent abscisic acid biosynthetic pathway in plants. Molecular Plant. doi:10.1016/j.molp.2021.09.008
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