The study of plants contributed to establishment of the foundation for modern biology. For example, it was observations first made in plants that led to two fundamental theories of biology—cell theory and genetics. Throughout the 20th century, plant biology continued to make contributions to the conceptual and technological advances in basic biology and biotechnology, although plant biology's contributions were not always recognized by the field of biology at large. Plants have direct applications to today's major societal challenges including food security, climate change, energy, and sustainability. Solutions to these challenges require innovative technologies that are solidly based on science.

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Japanese butterbur (Petasites japonicus) is a perennial herbaceous plant belonging to the Compositae. The petioles are used mainly as a human food source, and ‘Aichi-Wase-Fuki,’ the most widely grown cultivar, is triploid and propagated vegetatively. Growth problems have been caused by three types of wide-spreading virus, arabis mosaic virus, butterbur mosaic virus and cucumber mosaic virus in Osaka Prefecture. To establish efficient mass propagation of virus-free plants, adventitious buds were regenerated directly from immature flowerheads of Japanese butterbur. Osaka native lines of Japanese butterbur were collected from the production field, and the highest yielding clonal line was selected by comparison cultivation using virus-free plants regenerated from the collections. To induce somaclonal variation related to plant yield, adventitious buds were regenerated directly from immature flowerheads of Japanese butterbur. The total yield of the highest-yielding variant induced by somaclonal variation was 20.89 t/ha, which was 129.8% that of ‘Aichi-Wase-Fuki’. Subsequently, the highest yielding variant was registered in 2002 as ‘Osaka-Nougi-Ikusei No.1.’ Currently, all farmers in Osaka Prefecture cultivate this high-yield cultivar ‘Osaka-Nougi-Ikusei No.1.’

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A high affinity transport system (HATS) for nitrate in plants is operated by a two-component NRT2/NAR2 transport system. However, the regulation and localization of NRT2 and NAR2 at protein level are largely unknown and especially so in crop plant species. In this study with barley (Hordeum vulgare), membrane localization, protein expression in the roots, and a direct protein-protein interaction of HvNRT2 and HvNAR2 proteins were investigated. Immunochemical analysis showed that both HvNRT2 and HvNAR2 proteins were co-localized in the plasma membrane of the roots. Expression of HvNRT2 and HvNAR2 proteins was more strongly induced by treatment with higher concentrations of external nitrate, while HATS activity and transcripts for HvNRT2 and HvNAR2 were markedly repressed. An affinity column binding analysis using recombinant proteins suggests that the C-terminus of HvNRT2.1 is possibly involved in its binding to the HvNAR2.3 central region and that the Ser463 present in the HvNRT2.1 C-terminus plays a role in the binding ability.

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We characterized the expression pattern of Atropa belladonna salicylic acid (SA) carboxyl methyltransferase gene, AbSAMT1, encoding S-adenosyl-L-methionine (SAM): SA carboxyl methyltransferase (SAMT) in A. belladonna, after the application of biotic and abiotic stresses to plants. AbSAMT1 was expressed after treatments of exogenous SA and also 1,2-benzisothiazole-1,1-dioxide (BIT), which is a chemical inducer related to the SA-dependent response. Expression of the AbSAMT1 gene was also induced by infection of A. belladonna plants with Pseudomonas syringae pv. tabaci (Pst), when distinctive disease resistance symptoms were observed. Moreover, it was confirmed that the expression of the AbSAMT1 gene was also induced by physical wounding and methyl jasmonate (MeJA), as well as the disease resistance response. These results suggest that AbSAMT1 may play a dual regulation role of distinct signaling in A. belladonna plants, namely the signaling pathway of the SA-dependent response, and also a jasmonic acid (JA) dependent response in local regions.

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SHORT VEGETATIVE PHASE (SVP) encodes a MADS-box transcription factor and function as a floral repressor in Arabidopsis. Mutations in two clock genes LATE ELONGATED HYPOCOTYL (LHY) and CIRCADIAN CLOCK ASSOCIATED 1 (CCA1) (lhy;cca1) delay flowering time of Arabidopsis under continuous light (LL). Mutation in the SVP gene suppresses the late flowering phenotype of the lhy;cca1 under LL. Here, we describe isolation of three suppressors of late flowering and abnormal flower shape phenotypes of 35S:SVP plants as a first step to understanding molecular mechanisms of late flowering caused by lhy;cca1 and 35S:SVP in Arabidopsis under LL. Genetic analysis suggested that the suppressor phenotypes appeared to be caused by monogenic and recessive mutations.

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Micromolar concentrations of exogenously applied cytokinins can inhibit the growth of tobacco BY-2 (Nicotiana tabacum L. cv. Bright Yellow 2) cells and induce cell death. To determine whether the antiproliferative and cell death-inducing mechanisms of cytokinins are linked, we investigated the inhibition of cell cycle transition by the cytokinin benzyladenine using BY-2 cells. Mitotic index and flow cytometric analyses revealed that benzyladenine decreased the rate of cells entering the G2 and M phases a few hours after treatment of unsynchronized cells. Additionally, for cells synchronized in M phase, benzyladenine delayed (at 10 μM) or arrested (at 50 μM) cell cycle progression at G1. Expression patterns of cell cycle-related genes (PCNA and A3-, A1- and B1-type cyclins) also indicated G1 arrest by a 50 μM benzyladenine treatment at the M or G1 phase. Cell cycle arrest was detected prior to the induction of cell death by the treatment. Increase in number of dead cells was observed 16 h after each treatment at M or G1, suggesting that cell death may not be induced when cells reach a specific time point in G1 phase but, rather, in a time-dependent manner following benzyladenine treatment.

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Using clonal in vitro propagated plantlets of Curcuma longa, the effects of light and cytokinin on micropropagation and microrhizome formation were investigated. The results showed the promotive effects of low light intensity for micropropagation and of short day condition for well-developed microrhizome induction. In the tissue of well-developed microrhizomes, differentiation of yellowish-pigmented cells similar to the secretory cells of rhizome of the mother plant was observed. Staining of the cells with nile red suggested the accumulation of essential oil. Rapidly growing callus was isolated from the root tip of micropropagated plantlets which retained totipotency during subculture. High concentration of kinetin induced microrhizome formation in this callus. Yellow pigmented cells were also observed in the tissue of microrhizome, although far less frequency.

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Agrobacterium strain EHA101 harboring plasmid pIG121-Hm containing the genes for β-glucuronidase (gus), hygromycin phosphotransferase (hpt) and neomycin phosphotransferase (nptII) was co-cultivated with leaf explants from in vitro grown spinach plants. Hygromycin-resistant calli were obtained 1 month after selection of transformed cells on 2.5 g l⁻¹ gellan gum-solidified MS medium containing 30 g l⁻¹ sucrose, 0.5 mg l⁻¹ 2,4-D, 2 mg l⁻¹ kinetin, 20 mg l⁻¹ hygromycin and 20 mg l⁻¹ meropenem trihydrate. Regeneration of adventitious shoots was affected by culture temperature, and the highest frequency of shoot formation was 40% when the calli were cultured at 14°C during regeneration process on 2.5 g l⁻¹ gellan gum-solidified MS medium containing 30 g l⁻¹ sucrose, 0.01 mg l⁻¹ 2,4-D, 1 mg l⁻¹ kinetin, 1 mg l⁻¹ gibberellic acid (GA3), 20 mg l⁻¹ hygromycin and 10 mg l⁻¹ meropenem trihydrate. Stable expression of gus gene was indicated by histochemical GUS assay in the leaves and roots of putative transgenic plants. Southern blot analysis of genomic DNA isolated from T0 plants confirmed the successful integration of T-DNA into the plant genome. Segregation of the gus gene in transgenic T1 progeny was confirmed by PCR analysis. These results show that Agrobacterium-mediated transformation combined with plant regeneration at a low temperature, 14°C, can be efficiently used for producing transgenic spinach plants with useful genes.

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Agrobacterium-mediated genetic transformation was applied to produce transgenic plants of spinach (Spinacia oleracea) resistant to 2 pest species, Trichoplusia ni and Autographa nigrisigna. Leaf segments from in vitro spinach plants of cultivar ‘Glory’ were co-cultivated with A. tumefaciens strain EHA105, which harbored the plasmid pBE2111FMB containing a synthetic cry1Ac gene encoding an insecticidal crystal protein of Bacillus thuringiensis, and neomycin phosphotransferase II and bialaphos resistance genes as selectable marker genes. Kanamycin (Km)-resistant calluses were obtained from co-cultivated leaf segments 1 month after selection on 2.5 g l⁻¹ gellan gum-solidified MS medium containing 30 g l⁻¹ sucrose, 0.5 mg l⁻¹ 2,4-dichlorophenoxyacetic acid (2,4-D), 2 mg l⁻¹ kinetin, 100 mg l⁻¹ Km and 20 mg l⁻¹ meropenem trihydrate. Regeneration of adventitious shoots from Km-resistant calluses was performed on 2.5 g l⁻¹ gellan gum-solidified MS medium containing 30 g l⁻¹ sucrose, 0.01 mg l⁻¹ 2,4-D, 1 mg l⁻¹ kinetin, 1 mg l⁻¹ gibberellic acid, 100 mg l⁻¹ Km and 10 mg l⁻¹ meropenem trihydrate at 14°C. PCR and Southern blot analyses of genomic DNA isolated from T1 plants confirmed the successful integration of T-DNA into the plant genome. Expression of Cry1Ac protein was confirmed in leaves of transgenic plants by Western blot analysis. Insect bioassays against T. ni and A. nigrisigna performed with T1 plants showed more than 93.3% insect mortality within 1 week. These results suggest that the cry1Ac gene was effectively expressed in spinach.

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Rosmarinic acid (RA), one of the main phenolic compounds in sweet basil (Ocimum basilicum L.), has antiviral, antimicrobial, and anti-inflammatory pharmacological properties. As recent studies have shown that UV-B and blue light irradiation stimulate phenylpropanoid biosynthesis, we determined whether light conditions affect RA content and antioxidant activity. Both antioxidant activity and phenolic content were increased by continuous white light irradiation. Ultra performance liquid chromatography analysis of the phenolic content of a methanolic extract of sweet basil revealed the presence of RA, caffeic acid and chicoric acid. Red and white light irradiation induced RA accumulation up to a level of 6 mg g⁻¹ fresh weight within 14 days, whereas blue light irradiation only induced RA accumulation up to a level of 3 mg g⁻¹ fresh weight, suggesting that the red wavelength at 600–700 nm in both white and red irradiation promoted the RA accumulation. In addition, RA accumulation was dependent on the irradiation period and was greater in the upper leaves than in the lower leaves. These results indicate that continuous white light is effective in increasing the RA content of basil, which results in high antioxidant activity.

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Plant genomes contain more than 120 genes encoding ATP-binding cassette (ABC) proteins, which can be classified into 8 groups. Among them, ABCC/MRP (Multidrug resistance-associated protein) family members are proposed to function in general as MgATP-energized pumps involved in detoxification mechanisms, mainly by transporting glutathione-xenobiotic (GS-X) conjugates and other bulky amphipathic anions across membranes. Recent reports demonstrated that 15 ABCC subfamily members in Arabidopsis thaliana are widely expressed in the plant body and suggested that these proteins play a general function for the survival of plant cells. In this study, it was found that a member of this family, AtABCC11, which was thought to encode a full-sized ABCC-type transporter, gives an unusual transcript of a much smaller size than the full-size mRNA covering the entire open reading frame, and therefore may not be functional as a full-sized ABC transporter in plants. This study also assessed the promoter activity of AtABCC11 compared with its closest paralogue, AtABCC12.

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