Biology subjects

Hirasawa, T.

Publications and source records attributed to Hirasawa, T..

4 recordsLinked to original sources

bioRxiv2026

Natural variation in rice mitogen-activated protein kinase 4 contributes to increased photosynthetic rate under field conditions

Improving rice (Oryza sativa L.) yield requires a balanced enhancement of both sink size and source capacity. While many QTLs for sink size have been identified, only a few are known for source capacity, which is essential for achieving high yield. Here we identified qHP10 as a major QTL for increased photosynthetic rate by using chromosome segment substitution lines derived from a cross between the high-yielding indica cultivar Takanari and the average-yielding japonica cultivar Koshihikari. High-resolution mapping combined with CRISPR/Cas9-induced mutagenesis revealed that the causative gene underlying qHP10 is Mitogen-Activated Protein Kinase 4 (OsMPK4). A near-isogenic line carrying the OsMPK4Takanari allele (NIL-OsMPK4) had a 15-25% higher photosynthetic rate than Koshihikari. NIL-OsMPK4 also had higher stomatal conductance than Koshihikari but similar stomatal pore size and density, indicating that increased stomatal aperture increases photosynthetic rate. This enhancement is likely attributable to the down-regulation of OsMPK4 expression, which increases stomatal conductance and thus promotes CO2 uptake. Our findings demonstrate that OsMPK4 is a promising genetic target for increasing source capacity and, potentially, rice yield through molecular breeding. (175 words)

plant biology↗

bioRxiv2026

Divergent mechanics of inner ear morphogenesis are coupled to developmental tempo over vertebrate evolution

Vertebrate embryos vary in size and developmental tempo based on reproductive strategies; however, organs of ancient origin, such as the eye and inner ear, remain highly conserved in structure and function. How both diverse embryonic traits and conserved organ development occur remains unclear. Here, we identify divergent morphogenetic mechanics of inner ear development, particularly in vesicular primordium expansion, in 12 species representing the major vertebrate lineages. Differences in cell volume regulation determine tissue growth mechanics, which diversify the expansion process but yield a conserved morphological outcome. Heterochronic shifts in organogenesis allow this regulation to evolve in coordination with a prolonged developmental period. These findings suggest that alternative morphogenetic mechanics mitigate the effects of diversified embryonic traits, thereby ensuring consistent morphological outcomes for highly conserved organs.

evolutionary biology↗

bioRxiv2024

New soft tissue data of pterosaur tail vane reveals sophisticated, dynamic tensioning usage and expands its evolutionary origins

Pterosaurs were the first vertebrates to achieve powered flight. Early pterosaurs had long stiff tails with a mobile base that could shift their center of mass, potentially benefiting flight control. These tails ended in a tall, thin soft tissue vane that would compromise aerodynamic control and efficiency if it fluttered excessively during flight. Maintaining stiffness in the vane would have been crucial in early pterosaur flight, but how this was achieved has been unclear, especially since vanes were lost in later pterosaurs and are absent in birds and bats. Here we use Laser-Stimulated Fluorescence imaging to reveal a cross-linking lattice within the tail vanes of early pterosaurs. The lattice supported a sophisticated dynamic tensioning system used to maintain vane stiffness, allowing the whole tail to augment flight control and the vane to function as a display structure.

paleontology↗

bioRxiv2022

Lung evolution in vertebrates and the water-to-land transition

A crucial evolutionary change in vertebrate history was the Palaeozoic (Devonian ~400 million years ago) water-to-land transition, allowed by key morphological and physiological modifications including the acquisition of lungs. Nonetheless, the origin and early evolution of vertebrate lungs remain highly controversial, particularly whether the ancestral state was paired or unpaired. Due to the rarity of fossil soft tissue preservation, lung evolution can only be traced based on the extant phylogenetic bracket. Here we investigate, for the first time, lung morphology in extensive developmental series of key living lunged osteichthyans using synchrotron X-ray microtomography and histology. Our results shed light on the primitive state of vertebrate lungs as unpaired, evolving to be truly paired in the lineage towards the tetrapods. The water-to-land transition confronted profound physiological challenges and paired lungs were decisive for increasing the surface area and the pulmonary compliance and volume, especially during the air-breathing on land.

evolutionary biology↗