Biology subjects

Kajita, T.

Publications and source records attributed to Kajita, T..

3 recordsLinked to original sources

bioRxiv2024

Global distribution of a land plant by means of oceanic dispersal

The geographic range of species is one of the key indicators of their evolutionary success. Unlike animals, most plants are immobile and expand their range primarily through long-distance dispersal (LDD) of seeds. Seeds can be dispersed over very long distances, especially by ocean currents. However, little is understood about the role of ocean currents in LDD and the contribution of land barriers to genetic differentiation on a global scale. To investigate the outermost limits of LDD by ocean currents in land plants, we studied Canavalia rosea (Sw.) DC. (Fabaceae), which is distributed throughout littoral areas of the tropics and subtropics around the world. Our results using DNA sequences from six chloroplast regions and two low-copy nuclear loci from 436 individuals in 37 populations revealed that ocean currents played a crucial role in the species range expansion and maintaining its global distribution despite the constraints by continental barriers. These suggest that the global distribution of C. rosea is the result of recent transoceanic dispersal within and between the Atlantic and Indo-Pacific oceans, while the Isthmus of Panama has prevented gene flow across the American continents. These results highlight the power of oceanic seed dispersal in shaping plant biogeography.

evolutionary biology↗

bioRxiv2024

Modulation of photosystem II heterogeneity and stomatal functioning contribute to sustaining photochemistry and photoprotection in mangroves exposed to a cold wave

Cold waves restrict the distribution of mangroves. This study examined the contribution of PSII heterogeneity and stomatal functioning to sustaining photochemistry and photoprotection in mangroves during a cold wave. We exposed eight populations of Kandelia obovata (cold-tolerant) and, Bruguiera gymnorhiza (cold-susceptible) from different latitudes to 27/20{degrees}C (favorable) and 10/3{degrees}C (chilling; simulated cold wave) day and night temperatures. Multiple trait responses imply that cold waves affected K. obovata the least. Significant changes in chlorophyll fluorescence transients (photosystem II [PSII]) with a slight decrease in the redox status of P700 (photosystem I [PSI]) imply a greater impact of a cold wave on PSII. During the cold wave, photochemical efficiency of PSII, efficiency of the water-splitting complex, light absorptance, stomatal pore area, cyclic electron flow, nonphotochemical quenching, and number of active PSII and PSII QB reducing centers decreased, while light transmittance, night respiration, and inactive PSII QB nonreducing, PSII{beta}, and {gamma} centers increased in both species. The population of K. obovata from the coldest latitudinal site (Fujian, China) was least affected by cold wave due to local evolutionary adaptations. Modulation of PSII heterogeneity and stomatal functioning is important to sustaining photochemistry and photoprotection in mangroves to cope with cold waves. HighlightsPSII heterogeneity and stomatal functioning support mangroves to cope with cold waves. Local evolutionary adaptations promote the cold tolerance of mangrove populations.

plant biology↗

bioRxiv2020

Massive rhizobial genomic variations associated with partner quality in Lotus-Mesorhizobium symbiosis

In diverse mutualistic relationships, genetic variations in impact on the growth of interacting partners--variations in partner quality--are common, despite the theoretical prediction that selection favoring high-quality partners should eliminate such variations. Here, we investigated how variations in partner quality could be maintained in the nitrogen-fixing mutualism between Lotus japonicus and Mesorhizobium bacteria. We reconstructed de novo assembled full-genome sequences from nine rhizobial symbionts, finding massive variations in the core genome and the contrastingly similar symbiotic islands, indicating recent horizontal gene transfer (HGT) of the symbiosis islands into diverse Mesorhizobium lineages. A cross-inoculation experiment using nine sequenced rhizobial symbionts and 15 L. japonicus accessions revealed extensive quality variations represented by plant growth phenotypes, including genotype-by-genotype interactions. Quality variations were not associated with the presence/absence variations of known symbiosis-related genes in the symbiosis island, but rather, showed significant correlations with the core genome variations, supported by SNP- and kinship matrix-based association analyses. These findings highlight the novel role of HGT of symbiosis islands, which indirectly supply mutations of core genomes into L. japonicus-associated bacteria, thereby contributing to the maintenance of variations in partner quality.

evolutionary biology↗