Biology subjects

Asami, T.

Publications and source records attributed to Asami, T..

5 recordsLinked to original sources

bioRxiv2025

In Vitro Dynamic and Quantitative Monitoring of Strigolactone-signaling Complex Formation by Time-resolved FRET

SummaryStrigolactones (SLs) are a class of plant hormones that play a critical role in the suppression of shoot branching. Furthermore, they are exuded from roots and act as signaling molecules for inter-organism communication in the rhizosphere. Strigolactones trigger those responses by inducing protein-protein interactions (PPIs) of signaling components and subsequent proteolysis of transcriptional repressors. The sequential event involves SL hydrolysis mediated by SL receptors belonging to an /-hydrolase family, although the physiological role of SL hydrolysis is a subject of debate. To date, SL-induced PPIs have been analyzed by methods such as yeast-two hybrid, pull-down, and AlphaScreen assays. However, the kinetic aspect of PPI profiles has not been well studied. Here, we developed an in vitro method to monitor the formation of the SL signaling complex based on Time-Resolved Forster Resonance Energy Transfer (TR-FRET) technology. Our TR-FRET-based assay system allows us to analyze the mode of action of SL analogs from kinetic and quantitative perspectives. Notably, our method revealed differences in the intensity and time-dependency of PPI signals among different SL analogs with a range of hydrolyzabilities. In addition, we found that tolfenamic acid, an antagonist of the SL receptor, inhibited the SL-induced PPI but could not disrupt the already-formed signaling complex. The TR-FRET system was also used to rapidly and specifically detect naturally occurring SLs from root exudates containing many impurities. This work provides insights into the molecular mechanism of SL perception as well as a powerful tool for activity-based screening of SL signaling modulators. Significance statementThe dual roles of strigolactone (SL) receptors in both the perception and deactivation of SLs make it difficult to elucidate the underlying molecular mechanism of SL signaling. We developed a new in vitro method to evaluate the dynamic activation of the SL receptor, and used it to gain deeper insights into the molecular mechanism of SL-signaling complex formation in response to the SL receptor agonists.

plant biology↗

bioRxiv2024

Identification and Characterization of Compounds that Improve Plant Photosynthesis and Growth under Light Stress Conditions.

In order to satisfy the food and fuel demands of a growing population, global food production needs to increase by more than 50% before 2050. However, various environmental stresses in the natural environment inhibit plant growth and result in reduced yields. This is primarily caused by decreases in photosynthetic capacity. Thus, there is an urgent need to develop new strategies to improve agricultural productivity and ensure food security. In this study, a novel chemical-screening system with 96 well plates and leaf disks of tobacco was used to identify several anthraquinone derivatives that could relieve high light stress from plants. Treatments with these chemicals induced greater photosynthetic capacity after high light stress conditions for 20-72 hours (h) in tobacco and better plant growth after exposure to light stress for 96 hours in Arabidopsis and lettuces. The photoprotective effect of anthraquinone derivatives is closely related to chemical induced oxidation of PSI. Furthermore, there were no negative effects on plant growth in chemically treated plants under non-stressful conditions. Taken together, this study shows that anthraquinone derivatives can confer high light stress tolerance in plants, resulting in improved plant photosynthesis and growth in environments with light stress.

plant biology↗

bioRxiv2022

Chemical genetic screening identifies nalacin as an inhibitor of GH3 amido synthetase for auxin conjugation

Root system is critical for plant growth and development. To develop plant growth regulators functioning in root development, we performed a phenotype-based chemical screen in Arabidopsis and identified a chemical, nalacin, that mimicked the effects of auxin on root development. Genetic, pharmacological and biochemical approaches demonstrated that nalacin exerts its auxin-like activities by inhibiting indole-3-acetic acid (IAA) conjugation that is mediated by Gretchen Hagen 3 (GH3) acyl acid amido synthetases. The crystal structure of Arabidopsis GH3.6 in complex with D4 (a derivative of nalacin) together with docking simulation analysis revealed the molecular basis of the inhibition of group II GH3 by nalacin. Sequence alignment analysis indicated broad bioactivities of nalacin and D4 as inhibitors of GH3s in vascular plants, which were confirmed, at least, in tomato and rice. In summary, our work identifies nalacin as a potent inhibitor of IAA conjugation mediated by group II GH3 that plays versatile roles in hormone-regulated plant development and has potential applications in both basic research and agriculture.

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↗

bioRxiv2018

Triazole ureas covalently bind to strigolactone receptors and regulate signaling

Strigolactones (SLs), a class of plant hormones with multiple functions, mediate plant-plant and plant-microorganism communications in the rhizosphere. In this study, we developed potent strigolactone antagonists, which covalently bind to the strigolactone receptor D14, by preparing an array of triazole urea compounds. Using yeast two-hybrid assays and rice tillering assays, we identified a triazole urea compound KK094 as a potent inhibitor of strigolactone receptors. The LC-MS/MS analysis and X-ray crystallography concluded that KK094 was hydrolyzed by D14, and that a reaction product of this degradation covalently binds to the Ser residue of the catalytic triad of D14. We also identified KK052 and KK073, whose effects on D14-D53/D14-SLR1 complex formation were opposite due to a trifluoromethyl group on its benzene ring. These results demonstrate that triazole urea compounds are potentially powerful tools for agricultural application and may be useful for the elucidation of the complicated mechanism underlying SL-perception.

plant biology↗