Strigolactones (SLs) are a novel class of phytohormones that shape shoot and root architecture. Carlactone, the precursor of SLs, is synthesized from all-trans-β-carotene by the sequential action of three enzymes: the all-trans/9-cis-β-carotene isomerase DWARF27 (D27) that reversibly converts all-trans-β-carotene into 9-cis-β-carotene (shown only for the rice D27) and the carotenoid cleavage dioxygenases 7 and 8 (CCD7 and CCD8). Genomes of higher plants encode two D27 homologs (D27-like 1 and D27-like 2) with unknown function. Rice and Arabidopsis d27 mutants show less pronounced high tillering/more branching phenotype, compared to ccd7 or ccd8 mutants. This difference might be the result of functional redundancy caused by the presence of D27-like 1 and D27-like 2. In this study, we investigated the enzymatic and biological activity of the Arabidopsis D27 and the rice and Arabidopsis D27-like 1, using both in vivo and in vitro studies. Our results show that AtD27 is a true ortholog of the rice D27. Like SLs, the biosynthesis of ABA requires an all-trans/9-cis-isomerization reaction. However, the enzyme postulated for this activity is still elusive. Our enzymatic activity tests exclude a direct involvement of AtD27 in ABA biosynthesis. Nevertheless, Atd27 mutant shows low level of ABA, and analysis of AtD27 promoter
| Identifer | oai:union.ndltd.org:kaust.edu.sa/oai:repository.kaust.edu.sa:10754/630146 |
| Date | 10 1900 |
| Creators | Abuauf, Haneen W. |
| Contributors | Al-Babili, Salim, Biological and Environmental Sciences and Engineering (BESE) Division, Tester, Mark A., Arold, Stefan T., Zurbriggen, Matias |
| Source Sets | King Abdullah University of Science and Technology |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Rights | 2019-12-04, At the time of archiving, the student author of this dissertation opted to temporarily restrict access to it. The full text of this dissertation became available to the public after the expiration of the embargo on 2019-12-04. |
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