Tomotsugu Koyama

Summary: Cell expansion is crucial for organ morphogenesis in multicellular organisms. Apoplast acidification triggers plant cell expansion. Plant hormones and transcription factors such as TEOSINTE BRANCHED, CYCLOIDEA, and PROLIFERATING CELL NUCLEAR ANTIGEN BINDING FACTORs (TCPs) control cell expansion. However, details regarding the regulatory mechanism of cell expansion for organ morphogenesis remain unclear. In this study, we used molecular, biochemical, cellular, genetic, atomic force microscopy, and tensile testing analyses and showed that miR319‐targeted TCPs integrated cell expansion with organ morphogenesis in Arabidopsis thaliana . We found that TCPs directly induce the expression of genes encoding cell wall–loosening proteins and SMALL AUXIN UP RNAs (SAURs), activators of plasma membrane–localized H ⁺ ‐ATPases. TCP‐mediated activation of plasma membrane–localized H ⁺ ‐ATPases stimulates apoplast acidification, reduces cell wall stiffness, promotes cell expansion, and thus exaggerates elongation of the hypocotyl. Ectopic expression of a SAUR gene in sextuple tcp mutant plants substantially recovered the hypocotyl morphology of the tcp mutant, providing genetic evidence of TCP ‐mediated SAUR regulation. Collectively, our data show that TCPs regulate apoplast acidification for cell expansion.

Cell expansion is crucial for organ morphogenesis in multicellular organisms. Apoplast acidification triggers plant cell expansion. Plant hormones and transcription factors such as TEOSINTE BRANCHED, CYCLOIDEA, and PROLIFERATING CELL NUCLEAR ANTIGEN BINDING FACTORs (TCPs) control cell expansion. However, details regarding the regulatory mechanism of cell expansion for organ morphogenesis remain unclear. In this study, we used molecular, biochemical, cellular, genetic, atomic force microscopy, and tensile testing analyses and showed that miR319-targeted TCPs integrated cell expansion with organ morphogenesis in Arabidopsis thaliana. We found that TCPs directly induce the expression of genes encoding cell wall loosening proteins and SMALL AUXIN UP RNAs (SAURs), activators of plasma membrane-localized H+-ATPases. TCP-mediated activation of plasma membrane-localized H+-ATPases stimulates apoplast acidification, reduce cell stiffness, promote cell expansion, and thus exaggerate elongation of the hypocotyl. Ectopic expression of a SAUR gene in sextuple tcp mutant plants substantially recovered the hypocotyl morphology of the tcp mutant, providing genetic evidence of TCP-mediated SAUR regulation. Collectively, our data show that TCPs regulate apoplast acidification for cell expansion.

In plants, gene regulation underlies organ development and responses to environmental changes

Plants develop organs such as flowers and leaves with different morphologies

Production of beneficial lignans in heterologous host plants

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Rationale: The plant hormone auxin, indole‐3‐acetic acid, regulates many aspects of plant growth and development. Auxin quantification should offer broad insights into its mechanistic action in plants. However, limited auxin content in plant tissues hampers the establishment of quantification methods without the highest graded instruments or deeply specialized experimental techniques. Methods: In this study, we detailed optimized conditions for high‐performance liquid chromatography coupled with triple‐quadrupole mass spectrometry (LC/MS). We compared LC/MS conditions, such as columns, mobile phases, parameters of acquisition methods (selective or multiple ion monitoring), dwell times (DTs), and channel numbers, using differentially mixed authentic auxin and its related compounds. We further investigated pretreatment methods through the optimization of auxin recovery and irrelative compound removal from plant tissues prior to the LC/MS analysis. Results: Our LC/MS analysis demonstrated the particular importance of the column, DTs, and channel numbers on detection sensitivity. Our comparative analysis developed optimal pretreatment methods, including the pulverization of plants, concentration of extract through centrifugal evaporation, and removal of irrelative metabolites using liquid–liquid extraction and a spin filter. We injected plant samples into our LC/MS system, quantified auxin and eight related compounds in a single measurement, and determined the auxin increase in an auxin over‐producing mutant. Conclusions: Our practical optimization of LC/MS conditions and pretreatment methods provides detailed experimental processes toward the sensitive quantification of auxin from 10 mg of plant tissue. These processes have not always been clearly documented; therefore, our protocol could broadly contribute to technical advances in plant growth and development research.

Sesamin is a furofuran-type lignan that is found abundantly in seeds of Sesamum indicum (sesame) and has been widely accepted as a dietary supplement with positive effects on human health. The biological activity of sesamin in human cells and organs has been analysed extensively, although comparatively few studies show biological functions for sesamin in planta. Herein we screened sesamin-binding proteins (SBP) from sesame seedling extracts using sesamin-immobilized nano-beads. In subsequent peptide mass fingerprinting analyses, we identified a SBP, Steroleosin B, which is one of the membrane proteins found in oil bodies. In addition, pull-down assays and saturation transfer difference-nuclear magnetic resonance (STD-NMR) experiments demonstrated that sesamin binds directly to recombinant Steroleosin B in vitro. Finally, ectopic accumulations of sesamin and Steroleosin B in transgenic Arabidopsis thaliana plants induced severe growth defects including suppression of leaf expansion and root elongation. Collectively, these results indicate that sesamin influences tissue development in the presence of Steroleosin B.