Biology subjects

Lanfranco, L.

Publications and source records attributed to Lanfranco, L..

5 recordsLinked to original sources

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↗

bioRxiv2023

Disruption of the rice 4-DEOXYOROBANCHOL HYDROXYLASE unravels specific functions of canonical strigolactones

Strigolactones (SLs) regulate many developmental processes, including shoot-branching/tillering, and mediate rhizospheric interactions. SLs are structurally diverse, divided into a canonical and a non-canonical sub-family. To better understand the biological function of particular SLs, we generated CRISPR/Cas9 mutants disrupted in OsMAX1-1400 or OsMAX1-1900, which encode cytochrome P450 enzymes (CYP711A clade) contributing to SL diversity. The disruption of OsMAX1-1900 did neither affect the SL pattern nor plant architecture, indicating a functional redundancy. In contrast, disruption of OsMAX1-1400 activity, a 4-deoxyorobanchol hydroxylase, led to a complete lack of orobanchol and an accumulation of its precursor 4-deoxyorobanchol (4DO), both of which are a canonical SLs common in different plant species, accompanied by higher levels of the non-canonical methyl 4-oxo-carlactonoate (4-oxo-MeCLA). Os1400 mutants showed also shorter plant height, panicle and panicle base length, but did not exhibit a tillering phenotype. Hormone quantification and transcriptome analysis revealed elevated auxin levels and changes in the expression of auxin-related, as well as of SL biosynthetic genes. Interestingly, the Os900/1400 double mutant lacking both orobanchol and 4DO did not show the observed Os1400 architectural phenotypes, indicating that they are a result of 4DO accumulation. A comparison of the mycorrhization and Striga seed germinating activity of Os900, Os900/1400, and Os1400 loss-of-function mutants demonstrates that the germination activity positively correlates with 4DO content while disrupting OsMAX1-1400 negatively impact mycorrhizal symbiosis. Taken together, our paper deciphers the biological function of canonical SLs in rice and depicts their particular contributions to establishing architecture and rhizospheric communications.

plant biology↗

bioRxiv2023

Integration of Apocarotenoid Profile and Expression Pattern of Carotenoid Cleavage Dioxygenases during Mycorrhization in Rice

Carotenoids are susceptible to degrading processes initiated by oxidative cleavage reactions mediated by Carotenoid Cleavage Dioxygenases that break their backbone, leading to products called apocarotenoids. These carotenoid-derived metabolites include the phytohormones abscisic acid and strigolactones, and different signaling molecules and growth regulators, which are utilized by plants to coordinate many aspects of their life. Several apocarotenoids have been recruited for the communication between plants and arbuscular mycorrhizal (AM) fungi and as regulators of the establishment of AM symbiosis. However, our knowledge on their biosynthetic pathways and the regulation of their pattern during AM symbiosis is still limited. In this study, we generated a qualitative and quantitative profile of apocarotenoids in roots and shoots of rice plants exposed to high/low phosphate concentrations, and upon AM symbiosis in a time course experiment covering different stages of growth and AM development. To get deeper insights in the biology of apocarotenoids during this plant-fungal symbiosis, we complemented the metabolic profiles by determining the expression pattern of CCD genes, taking advantage of chemometric tools. This analysis revealed the specific profiles of CCD genes and apocarotenoids across different stages of AM symbiosis and phosphate supply conditions, identifying novel markers at both local and systemic levels. HighlightOur study presents the profiles of CCD gene expression and apocarotenoids across different stages of AM symbiosis and Pi supply conditions and reveals novel AM markers at both local and systemic levels.

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

Canonical Strigolactones Are Not the Tillering-Inhibitory Hormone but Rhizospheric Signals in Rice

The plant hormones strigolactones (SLs) regulate shoot branching and mediate the communication with symbiotic mycorrhizal fungi, but also with noxious root parasitic weeds, such as Striga spp. SLs derive from carlactone (CL) and are divided structurally into canonical and non-canonical SLs. However, the questions about particular biological functions of the two groups and the identification of the SL that inhibits shoot branching are still unanswered, hampering targeted modification of SL pattern towards improving plant architecture and resistance against Striga. Here, we reported that 4-deoxyorobanchol (4DO) and orobanchol, the two canonical SLs in rice, do not have major role in determining rice shoot architecture. CRISPR/Cas9 mediated Osmax1-900 mutants, lacking these two SLs, do not show the high tillering and dwarf phenotype typical for SL-deficient plants. However, the absence of 4DO and orobanchol in root exudates significantly decreased their capability in inducing Striga seed germination, while caused only a delay in root colonization by mycorrhizal fungi. To confirm the genetic evidence, we used the SL-biosynthesis inhibitor TIS108. Our results showed that TIS108 is a MAX1-specific inhibitor that lowers 4DO and orobanchol synthesis, conferring a resistance to Striga without a severe impact on rice architecture. Hence, our work uncovers the specific function of canonical SLs as rhizospheric signals and paves the way for establishing chemical and genetic based approaches for combating the root parasitic weeds, by targeted depletion of their release.

plant biology↗