Biology subjects

Ablazov, A.

Publications and source records attributed to Ablazov, A..

4 recordsLinked to original sources

bioRxiv2024

DWARF14 and KARRIKIN INSENSITIVE2 mediate signaling of the apocarotenoid zaxinone in Arabidopsis

The natural growth regulator zaxinone increases the levels of the phytohormones strigolactone (SL) and abscisic acid in Arabidopsis (Arabidopsis thaliana) via unknown mechanisms. We demonstrate that parts of the effects of zaxinone in Arabidopsis depend on the SL receptor DWARF14 (AtD14), the karrikin receptor KARRIKIN INSENSITIVE2 (AtKAI2), and the F-Box protein MORE AXILLARY BRANCHING2 (AtMAX2) that mediates the signaling of SLs and karrikins. Binding assays and co-crystallization revealed zaxinone as an additional ligand of AtD14 and an SL antagonist that interrupts the interaction of AtD14 with AtMAX2. Zaxinone also bound to AtKAI2. These findings unveil a perception mechanism for zaxinone in Arabidopsis and demonstrate the capability of AtD14 and AtKAI2 to bind signaling molecules, other than strigolactones or karrikins, and mediate their transduction.

plant biology↗

bioRxiv2023

Zaxinone Synthase overexpression modulates rice physiology and metabolism, improving growth and productivity under normal and low phosphate supply

The rice Zaxinone Synthase (ZAS) gene encodes a carotenoid cleavage dioxygenase (CCD) that forms the apocarotenoid growth regulator zaxinone. Here, we generated and characterized constitutive ZAS-overexpressing rice lines, to better understand ZAS role in determining zaxinone content and regulating growth and architecture. ZAS overexpression enhanced endogenous zaxinone level, promoted root growth and meristem size, and increased the number of productive tillers, leading to an up to 30% higher grain yield per plant. Hormone analysis revealed a decrease in strigolactone (SL) content, which we confirmed by rescuing the high-tillering phenotype through application of a SL analog. Metabolomics analysis revealed that ZAS overexpressing plants accumulate higher amounts of monosaccharide sugars, in line with transcriptome analysis. Moreover, transgenic plants showed higher carbon (C) assimilation rate and elevated root phosphate, nitrate and sulfate level, enhancing the tolerance towards low phosphate (Pi) and indicating a generally better nutrient uptake. Our study shows that ZAS regulates hormone homeostasis and a combination of physiological processes to promote growth and grain yield, which makes this gene an excellent candidate for sustainable crop improvement. TeaserZaxinone Synthase overexpression modulates rice metabolism and physiology and improves growth and phosphate uptake.

plant biology↗

bioRxiv2022

ZAXINONE SYNTHASE 2 regulates growth and arbuscular mycorrhizal symbiosis in rice

Carotenoid cleavage, catalyzed by CAROTENOID CLEAVAGE DIOXYGENASES (CCDs), provides signaling molecules and precursors of plant hormones. Recently, we showed that zaxinone, a novel apocarotenoid metabolite formed by the CCD Zaxinone Synthase (ZAS), is a growth regulator required for normal rice growth and development. The rice genome encodes three OsZAS homologs, called here OsZAS1b, OsZAS1c, and OsZAS2, with unknown functions. Here, we investigated the enzymatic activity, expression pattern, and subcellular localization of OsZAS2, and generated and characterized loss-of-function CRISPR/Cas9-Oszas2 mutants. We show that OsZAS2 formed zaxinone in vitro. OsZAS2 is a plastid-localized enzyme mainly expressed in the root cortex under phosphate starvation. Moreover, OsZAS2 expression increased during mycorrhization, specifically in arbuscule-containing cells. Oszas2 mutants contained lower zaxinone content in roots and exhibited reduced root and shoot biomass, less productive tiller, and higher strigolactone (SL) levels. Exogenous zaxinone application repressed SL biosynthesis and partially rescued the growth retardation of Oszas2 mutant. Consistent with the OsZAS2 expression pattern, Oszas2 mutants displayed a lower frequency of AM colonization. In conclusion, OsZAS2 encodes a further zaxinone-forming enzyme that determines rice growth and architecture and strigolactone content and is required for optimal mycorrhization.

plant biology↗

bioRxiv2022

The Arabidopsis D27like1 is a novel Isomerase that Contributes to SL Biosynthesis and Negatively Impacts ABA Level

The enzyme DWARF27 (D27) catalyzes the reversible isomerization of all-trans- into 9-cis-{beta}-carotene, initiating strigolactone (SL) biosynthesis. Genomes of higher plants encode two D27-homologs, D27-like1 and -like2, with unknown functions. Here, we investigated the enzymatic activity and biological function of the Arabidopsis D27-like1. In vitro enzymatic assays and Expression in Synechocystis sp. PCC6803 revealed a yet not reported 13-cis/15-cis/9-cis- and a 9-cis/all-trans-{beta}-carotene isomerization. Although disruption of AtD27-like1 did not cause SL deficiency phenotypes, overexpression of AtD27-like1 in the Atd27 mutant restored the more-branching phenotype, indicating a contribution of AtD27-like1 to SL biosynthesis. Accordingly, generated Atd27 Atd27like1 double mutants showed more pronounced branching phenotype, compared to Atd27. The contribution of AtD27-like1 to SL biosynthesis is likely due to its formation of 9-cis-{beta}-carotene that was present at higher levels in AtD27-like1 overexpressing lines. In contrast, AtD27-like1 expression correlated negatively with the content of 9-cis-violaxanthin, a precursor of abscisic acid (ABA), in shoots. Consistently, ABA levels were higher in shoots and also in dry seeds of the Atd27like1 and Atd27 Atd27like1 mutants. Transgenic lines expressing {beta}-glucuronidase (GUS) driven by the AtD27LIKE1 promoter and transcript analysis performed with hormone-treated Arabidopsis seedlings unraveled that AtD27LIKE1 is expressed in different tissues and regulated ABA and auxin. Taken together, our work revealed a cis/cis-{beta}-carotene isomerase activity that affects the content of both cis-carotenoid derived plant hormones ABA and SLs.

plant biology↗