The University of Tokyo · Agricultural and Biological Sciences
Professor Hiroyuki Koga's research lab focuses on the evolutionary and developmental mechanisms underlying phenotypic plasticity and novel morphological structures in plants and echinoderms. The lab investigates heterophylly in amphibious plants like *Callitriche palustris*, exploring how environmental cues trigger distinct leaf forms through cellular and molecular mechanisms, including cytoskeletal reorganization and gene regulation. Additionally, the lab examines the evolutionary co-option of skeletogenic genetic networks in echinoderms, particularly the origin of the larval skeleton, to understand how complex structures evolve through developmental system drift and gene network recruitment. These studies integrate developmental biology, evolutionary genetics, and comparative genomics to uncover fundamental principles of morphological innovation.
Figures are computed from collected data and may differ slightly.
Heterophylly is the development of different leaf forms in a single plant depending on the environmental conditions. It is often observed in amphibious aquatic plants that can grow under both aerial and submerged conditions. Although heterophylly is well recognized in aquatic plants, the associated developmental mechanisms and the molecular basis remain unclear. To clarify these underlying developmental and molecular mechanisms, we analyzed heterophyllous leaf formation in an aquatic plant, Call
Over the course of evolution, the acquisition of novel structures has ultimately led to wide variation in morphology among extant multicellular organisms. Thus, the origins of genetic systems for new morphological structures are a subject of great interest in evolutionary biology. The larval skeleton is a novel structure acquired in some echinoderm lineages via the activation of the adult skeletogenic machinery. Previously, VEGF signaling was suggested to have played an important role in the acq
Heterophylly, or phenotypic plasticity in leaf form, is a remarkable feature of amphibious plants. When the shoots of these plants grow underwater, they often develop surprisingly different leaves from those that emerge in air. Among aquatic plants, it is typical for two or more distinct leaf development processes to be observed in the same individual exposed to different environments. Here, we analyze the developmental processes of heterophylly in the amphibious plant <i>Callitriche palustris</
Amphibious plants can grow and survive in both aquatic and terrestrial environments. This review explores the diverse adaptations that enable them to thrive in such contrasting habitats. Plants with amphibious lifestyles possess fascinating traits, and their phenotypic plasticity plays an important role in adaptations. Heterophylly, the ability to produce different leaf forms, is one such trait, with submerged leaves generally being longer, narrower, and thinner than aerial leaves. In addition t
The evolution of various body plans results from the acquisition of novel structures as well as the loss of existing structures. Some novel structures necessitate multiple evolutionary steps, requiring organisms to overcome the intermediate steps, which might be less adaptive or neutral. To examine this issue, echinoderms might provide an ideal experimental system. A larval skeleton is acquired in some echinoderm lineages, such as sea urchins, probably via the co-option of the skeletogenic machi
Six cases of extravasation from ruptured intracranial aneurysm during angiography were encountered during the past four years. Cerebral angiography was performed within several hours after the attack in each case. All had emergency radical operations and three of them survived.
A case of aneurysm arising from the posterior communicating artery itself clipped by contralateral frontotemporal craniotomy (pterional approach) is presented. A 65-year-old female developed sudden severe headache and chest pain in January of 1993. Neurological examination on admission revealed consciousness disturbance such as stupor and nuchal stiffness. CT-scan showed marked subarachnoid hemorrhage. She also suffered from acute myocardial ischemia and cardiac failure. Cerebral angiograms afte
To gain a better understanding of molluscan development and its relation to the evolution of their unique body plan, we performed a genomic survey of genes encoding transcription factors, such as Tbx, Fox, Ets, HMG, NFκB, bZIP, and C2H2 zinc finger proteins in the Japanese pearl oyster, Pinctada fucata. We annotated 133 transcription factor genes. Together with the orthologs of known deuterostome genes, we found several orphan genes in each class of transcription factor. Some possessed clear ort
A case was reported of cerebellopontine angle lipoma with vascular anomaly which was thought to be the remnant of fetal anastomosis of the posterior inferior cerebellar artery (PICA) and of the anterior inferior cerebellar artery (AICA). A 42 year-old man had been suffering from intermittent dizziness for a year. Worsening of dizziness after mild head trauma led him to visit a doctor who pointed out a cerebellopontine angle lesion. On admission to our hospital, neurological examination revealed
Abstract Heterophylly refers to the development of different leaf forms in a single plant depending on the environmental conditions. It is often observed in amphibious aquatic plants that can grow under aerial and submerged conditions. Although heterophylly is well recognized in aquatic plants, the associated developmental mechanisms and the molecular basis remain unclear. In this study, we analyzed heterophyllous leaf formation in an aquatic plant, Callitriche palustris , to clarify the underly
As master transcription factors of stomatal development, SPEECHLESS, MUTE, and FAMA, collectively termed SMFs, are primary targets of molecular genetic analyses in the model plant Arabidopsis thaliana. Studies in other model systems identified SMF orthologs as key players in evolutionary developmental biology studies on stomata. However, recent studies on the astomatous liverwort Marchantia polymorpha revealed that the functions of these genes are not limited to the stomatal development, but ext
We report the presence of a new naturalised terrestrial species, <i>Callitrichedeflexa</i>, which has been previously misidentified as <i>C.terrestris</i> because of its similar morphology. <i>Callitrichedeflexa</i> can be distinguished from <i>C.terrestris</i> through genetic differences and distinct morphological traits, such as longer pedicels. Re-examination of herbarium specimens in the Kanagawa Prefectural Museum of Natural History confirmed that most of the specimens labelled as <i>C.terr
de novo transcriptome asssembly sequences of <i>Callitriche stagnalis</i> and <i>Callitriche japonica</i>. Brief annotation tables are also included.
As master transcription factors of stomatal development, SPEECHLESS, MUTE, and FAMA, collectively termed SMFs, are primary targets of molecular genetic analyses in the model plant Arabidopsis thaliana. Studies in other model systems identified SMF orthologs as key players in evolutionary developmental biology studies on stomata. However, recent studies on the astomatous liverwort Marchantia polymorpha revealed that the functions of these genes are not limited to the stomatal development, but ext
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