A characteristic feature of plants is their ability to produce a vast array of metabolites, a trait shaped by their evolution into sessile organisms. Over the past three decades, I have contributed to the development of phytochemical genomics, a field that emerged during the genomic era. Our research group established advanced analytical platforms for plant metabolomics by integrating state-of-the-art instruments with informatics tools. By combining genomics, transcriptomics, and metabolomics, we uncovered novel gene functions and identified new metabolites and gene-metabolite networks. Our study encompassed a broad spectrum of metabolites ranging from primary products, such as amino acids, sulfur-containing compounds, and lipids, to specialized (secondary) compounds, including flavonoids, alkaloids, and terpenoids. Initially, our focus was on the model plant Arabidopsis thaliana; however, we later included crops such as rice and tomato, as well as medicinal plants. This review highlights the key aspects of my research journey.

Evapotranspiration is a critical factor that plays a pivotal role in irrigation and water resource planning. It is also a major influence with regard to global warming issues. Therefore, several studies have been performed on the estimation methods for evapotranspiration; however, the most prevalent method used over a long period to estimate evapotranspiration is the complementary relationship approach. Recently, this method was modified to improve its symmetry and accuracy. However, to achieve better performance, a different evapotranspiration estimation method using an inverse analysis of the Bowen ratio was proposed by us in an earlier study. In order to present a performance comparison of these different estimation methods, the reproducibility of three types of complementary relationship methods and inverse analysis methods was assessed in this study. Our study utilized data from FLUXNET2015 and evaluated the performance of the methods using regression analysis and root mean square error (RMSE) with data from 15 test sites, mainly located in the U.S.A., for a total period of 132 years. From the results, it was observed that the inverse analysis approach demonstrated a slightly better performance than the complementary relationship methods. This study provides a valuable direction for future research works on the estimation of evapotranspiration.

M-COPA (1), which contains diene and 3-picolylamine moieties in its side chain and seven stereogenic centers in a multisubstituted octalin skeleton, strongly inhibits the growth of several cancer cell lines. Expecting the improvement of conformational flexibility of basic and coordinating 3-pyridylmethylamino group on M-COPA and its physical properties, we efficiently synthesized its amine analogs by replacing its amide group with an amino group through the Weinreb amide-type Horner–Wadsworth–Emmons reaction. The cytotoxic properties of 1 and its analogs were evaluated against NCI-H226, a lung cancer cell line, HeLa, a cervical cancer cell line, and GIST-T1, a gastrointestinal stromal tumor cell line. The evaluation results indicated that the structural alteration from amide moiety to amine moiety lowered the pharmacological activity but remained strong cytotoxicity.

Tetrodotoxin (TTX), the pufferfish toxin, has the potential to cause fatal food poisoning because of its potent voltage-gated sodium channel (Na_v) blocking activity. 4-epiTTX, 11-norTTX-6(S)-ol, and 11-oxoTTX are the major TTX analogues found in marine animals; thus, their chemical properties and biological activities should be determined. In this study, these three TTX analogues were purified to a high level (purity >97%) from pufferfish and newts. The ratios of the hemilactal to the 10,7-lactone forms were determined using ¹H NMR, and ¹³C NMR data were also obtained. 4-epiTTX underwent considerable transformation to TTX in physiological conditions. The Na_v blocking activity of these analogues was evaluated by whole-cell patch-clamp recording using a human Na_v1.2, colorimetric cell-based assay and mouse bioassay. The toxicity equivalency factors (TEFs setting TTX 1) of the three analogues were estimated; 4-epiTTX (0.06), 11-norTTX-6(S)-ol (0.02), and 11-oxoTTX (1.2) using patch-clamp recording, and 11-norTTX-6(S)-ol (0.50) and 11-oxoTTX (0.42) using the mouse bioassay. These data confirmed the low Na_v blocking activity of 4-epiTTX and high activity of 11-oxoTTX.