Biology subjects

Yazaki, K.

Publications and source records attributed to Yazaki, K..

3 recordsLinked to original sources

bioRxiv2021

Excretion of triacylglycerol as a matrix lipid facilitating apoplastic accumulation of a lipophilic metabolite shikonin.

Plants produce a large variety of lipophilic metabolites, many of which are secreted by cells and accumulated in apoplasts. The mechanism of secretion remains largely unknown, because hydrophobic metabolites, which may form oil droplets or crystals in cytosol, inducing cell death, cannot be directly secreted by transporters. Moreover, some secondary metabolic lipids react with cytosolic components leading to their decomposition. Lipophilic metabolites should thus be solubilized by matrix lipids and compartmentalized by membrane lipids. The mechanism of lipophilic metabolite secretion was assessed using shikonin, a red naphthoquinone lipid, in Lithospermum erythrorhizon. Cell secretion of shikonin also involved the secretion of about 30% of triacylglycerol (TAG), composed predominantly of saturated fatty acids. Shikonin production was associated with the induction of large amounts of the membrane lipid phosphatidylcholine. Together with in vitro reconstitution, these findings suggest a novel role for TAG as a matrix lipid for the secretion of lipophilic metabolites.

plant biology↗

bioRxiv2020

Species-specific assembly of root-associated bacterial microbiota mediated by a combination of plant specialized metabolites

Plant specialized metabolites (PSMs) influence the taxonomic compositions of the root-associated microbiota; however, the underlying molecular mechanisms and evolutionary trajectories remain elusive. Here, we show that the bacterial genus Arthrobacter is predominant in the tobacco endosphere, and that its enrichment is mediated by a combination of two tobacco-specific PSMs, santhopine and nicotine The isolation and whole genome sequencing of a representative set of Arthrobacter strains identified independent genomic features, including but not limited to genes for santhopine and nicotine catabolism, which are associated with the colonization competence of tobacco roots. Taken together, these data suggest that plant species-specific root microbiota assembly is mediated by bacterial catabolism of a cocktail of PSMs synthesized by the host plant.

microbiology↗

bioRxiv2020

Diurnal metabolic regulation of isoflavones and soyasaponins in soybean roots

Isoflavones and soyasaponins are major specialized metabolites accumulated in soybean roots and secreted into the rhizosphere. Unlike the biosynthetic pathway, the transporters involved in metabolite secretion remain unknown. The developmental regulation of isoflavone and soyasaponin secretions has been recently reported, but the diurnal regulation of their biosynthesis and secretion still needs to be further studied. To address these challenges, we conducted transcriptome and metabolite analysis using hydroponically grown soybean plants at 6-hour intervals for 48 hours in a 12-h-light/12-h-dark condition. Isoflavone and soyasaponin biosynthetic genes showed opposite patterns in the root tissues; that is, the former genes are highly expressed in daytime, while the latter ones are strongly induced at nighttime. GmMYB176 encoding a transcription factor of isoflavone biosynthesis was upregulated from ZT0 (6:00 am) to ZT6 (12:00 am), followed by the induction of isoflavone biosynthetic genes at ZT6. The isoflavone aglycone content in the roots accordingly increased from ZT6 to ZT18 (0:00 am), accompanied by an increase in glucoside levels that peaked at ZT0. The isoflavone aglycone content in root exudates was kept consistent throughout the day, whereas that of glucosides increased at ZT6, which reflected the decreased expression of the gene encoding beta-glucosidase involved in the hydrolysis of apoplast-localized isoflavone conjugates. Co-expression analysis revealed that those isoflavone and soyasaponin biosynthetic genes formed separate clusters, which exhibited a correlation to ABC and MATE transporter genes. As summary, the results in this study indicated the diurnal regulation of isoflavone biosynthesis in soybean roots and the putative transporter genes responsible for isoflavone and soyasaponin transport.

plant biology↗