Suntory Foundation for Life Sciences

Kakadu plum (Terminalia ferdinandiana) reportedly has the highest ascorbic acid levels of all plants worldwide and its juice reactivates functions of the retinoblastoma gene (RB) product, a tumor suppressor gene. In this study, the juice of the Kakadu plum was fractionated to identify the constituent active compounds. A novel ellagitannin, named terminalagin, was isolated from Kakadu plum (Terminalia ferdinandiana) juice via bioassay-guided isolation. The structure was determined using spectroscopic analysis and partial hydrolysis. Terminalagin has a corilagin substructure and a 2,4-(S)-hexahydroxydiphenoyl (HHDP) ester moiety that is not usually found in natural products. The results of this study enrich the structural database of ellagitannins and should provide invaluable aid for their further utilization in cancer prevention.

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.

Dodders (Cuscuta spp.) is an obligated parasitic plant, which lost a large part of photosynthetic genes but gained host genes through parasitism-mediated horizontal gene transfer (HGT). Their migratory ecology across the world would contribute to complexity of the speciation via geographic isolation. Here we report the de novo genome assemblies of the two phylogenetically distinct dodders; C. chinensis (2n=4x=60) and C. campestris (2n=4x=60) that are classified into Clade B and Clade H of subgenus Grammica, respectively. Relatively low completeness of BUSCO genes ca.87% indicated progressive gene loss after evolution of parasitic lifestyle due to release from functional constraints as photosynthesis and organ development. Comparative genomics uncovered that both species are the genome size is completely different regardless of the same cytotypes and allopolyploid through the independent ancient hybridization between different parents. Various genomic rearrangements including 1) gene gain and loss events, 2) homoeologous recombination between two subgenomes and 3) the lineage-specific proliferation of transposable elements likely contribute to their genomic diversity and sexual isolation of the two lineages partly sharing their habitats. Our findings not only provide genomic basis to survey parental species for allopolyploidization but also help to understand unique speciation of parasitic dodders through these chromosomal natures.

Floral morphology is a crucial trait that determines the commercial value of ornamental plants and pollinator preference. Scaevola aemula (Fan Flower) typically develops bilaterally symmetrical flowers, but a recessive mutant with a radially symmetrical flower (peloric) has been isolated from a breeding population. In the present study, we explored the molecular basis of the floral traits of S. aemula. We found a genetic-phenotypic association for the CYCLOIDEA (CYC) gene SaCYC2, which is known as a regulatory gene for floral symmetry in various plants. The peloric flower line had a nonsense mutation immediately downstream of the start codon of SaCYC2 causing a loss of function. RNA-sequencing analysis revealed three paralogous CYC genes in S. aemula, but only SaCYC2 was preferentially expressed in the dorsal side of the petals. Moreover, we developed a co-dominant cleaved amplified polymorphic sequence (CAPS) marker based on the nonsense mutation to verify floral traits, thereby accelerating the selection and breeding of Scaevola spp. Our findings support the conserved function of CYC genes that determine aspects of floral morphology in Asteraceae.

Gamete release, an essential event for animals, is regulated by various factors including environmental stimuli, neural circuit, and endocrine molecules. In this study, we investigated the mechanisms regulating gamete release in the ascidian Ciona robusta, part of the sister group of vertebrates. Ciona is a hermaphrodite, releasing sperm first from orange-pigmented organ (OPO) at the end of the spermiduct, followed by eggs from the oviduct beneath the spermiduct knob-like structure. In this study, behavioral and morphological analyses revealed that this sequential release occurs because the knob-like structure compresses the oviduct opening at the onset of gamete release. Observations of transgenic Ciona expressing Kaede under the gonadotropin-releasing hormone 2 (Gnrh2) promoter showed that Gnrh2-expressing neurons and fibers accumulate in the epithelium around the spermiduct openings. In contrast, Gnrh1-expressing neurons are localized in the cerebral ganglion and project toward the ovary, suggesting distinct roles of GnRH1 and GnRH2 in reproductive regulation. RNA-seq and real-time PCR analyses revealed that Opsin2, Opsin3, beta-carotene-15,15'-monooxygenase (Bco), and several ion channel genes are specifically expressed in the OPO, along with Gnrh2. In situ hybridization showed that these genes are localized in the innermost OPO layer, suggesting that the OPO functions as a photoreceptive organ. Although, Gnrh2 expression has been considered low in adult Ciona, our study revealed strong OPO-specific expression with photoreceptive genes. Collectively, these findings suggest that GnRH2 plays a central role in gamete release regulation, potentially in coordination with the photoreceptive system, while GnRH1 may regulate ovarian functions. These results indicate that C. robusta employs distinct GnRH systems in a tissue-specific manner to regulate reproduction.

Iron (Fe) is essential for redox reactions, electron transfer reactions, and enzymatic activity in the body. In the food chain, organisms ultimately obtain iron from plants. Therefore, the ability of plants to absorb iron from their roots is of great importance to all living organisms. Poaceae plants, including rice, barley, maize, and other grains, secrete phytosiderophores, which are mugineic acid (MA) compounds, to absorb Fe from the soil and take it up via transporters present in the roots as MA–Fe(iii) complexes. The mechanisms underlying iron acquisition by MA and transporters have been elucidated by cryo-electron microscopy, including the structural dynamics in transporting the complex. Furthermore, because the iron complex absorption mechanism works efficiently in alkaline soils, we envision a practical strategy for growing rice plants in alkaline soils based on synthetic MA analogs.

SummaryThe effects and mechanisms of polyunsaturated fatty acids (PUFAs) including docosahexaenoic acid (DHA) and arachidonic acid (ARA) contained in the lipid membrane of neurons in the production of amyloid β (Aβ), a pathogenic molecule in Alzheimer’s disease (AD), remain unclear. In this study, we cultured human cortical neurons differentiated from induced pluripotent stem cells (iPSCs) under conditions of PUFA deficiency being progressively alleviated. Under PUFA-deficient conditions, increasing the total PUFA composition ratio in the lipid membrane enhanced membrane fluidity and reduced Aβ production. Furthermore, in conditions where the overall PUFA deficiency was resolved, altering the specific ratios of DHA and ARA promoted the synchronous activity and morphological complexity of neuronal cells while maintaining consistent membrane fluidity. These findings demonstrate that the overall PUFA composition in the lipid membrane as well as the specific ratios of DHA and ARA within the total PUFAs regulate neuronal function and pathophysiology.

Mammalian follicle growth development is mainly regulated by the hypothalamus-pituitary-gonadal axis after puberty. Although pituitary hormones, gonadotropins, are involved in hypothalamus-pituitary-gonadal axis signaling, they are not responsible for the growth of early stage follicles, namely, primordial follicles, primary follicles, and secondary follicles, in both sexually immature and mature individuals. Unlike those of gonadotropin-dependent follicle growth, the specific regulatory factors of gonadotropin-independent follicle growth have yet to be identified. Here, we identified tachykinins (TKs) as inducers of gonadotropin-independent secondary follicle growth. TKs play various roles as neuropeptides or hormones in a wide variety of biological events both in the central nervous system and in peripheral tissues, but a direct effect of TKs on ovarian follicles has yet to investigated. Follicle development was suppressed in sexually immature 3-week-old KO mice of Tac1 gene encoding TKs (substance P and neurokinin A), which is independent of gonadotropins. TKs and their receptors are specifically localized to granulosa cells in mouse secondary follicles. Furthermore, TKs upregulate the prostaglandin (PG) synthase cyclooxygenase 2 via the Janus kinase 1-signal transducers and activators of transcription protein 3 signaling cascade. We also demonstrated that PGE2 and PGF2α are major PGs in the immature ovary, and the secondary follicle growth was enhanced by interaction between PGE2-PGF2α and their receptors, PGE2 receptor localized in the oocyte membrane and PGF2α receptor localized in the oocyte membrane, granulosa cells, and theca cells. Consequently, this study paves the way for exploring gonadotropin-independent early stage follicle growth systems and relevant dysfunctions, including pediatric endocrinological diseases.

Linalool is anticipated to have significant ecological roles. In this study, linalyl 6-O-α-arabinopyranosyl-β-d-glucopyranoside (linalyl β-vicianoside: LinVic) was synthesized, and a linalool diglycoside purified from soybean leaves was identified as LinVic by using liquid chromatography-mass spectrometry. High levels of LinVic were detected in leaves and sepals during soybean plant growth. The LinVic content did not significantly increase following methyl jasmonate treatment of the leaves, indicating that its synthesis is independent of the jasmonic acid signaling pathway. In addition to LinVic, soybean also contains 1-octen-3-yl primeveroside. We treated soybean leaves with vaporized linalool and 1-octen-3-ol to determine whether the glycosylation system discriminates between these 2 volatile alcohols. Linalool treatment resulted in the accumulation of LinVic, while 1-octen-3-ol treatment caused little change in the amount of 1-octen-3-yl primeveroside, suggesting discrimination between these compounds. Linalool-treated soybean leaves exhibited increased resistance against common cutworms, indicating that LinVic may contribute to herbivore resistance.