Human impacts on pine-dominated vegetation in rural landscapes in Korea and western Japan

To understand the human influence on the successional process of vegetation, structures of the pine forest as a dominant vegetation were compared between in Yanghwa-ri of rural Korea and Miwa-cho of rural Japan. The secondary pine forests are well developed around the villages in both regions. In rural Korea, pine forests are still used intensively for several traditional purposes. The pine forests in Yanghwa-ri of Korea, therefore, are stayed in the early stage of the succession. The floristic composition in pine forests of Yanghwa-ri was similar to that in the secondary grasslands. The fertilizer trees such as Robinia and Alnus contributed to develop the stratification of the forest. On the other hand, in Japan, almost all pine forests in rural regions had been abandoned due to the changing of traditional use because of the economic growth and the development of alternative energy sources since 1960s. In the case of pine forests of Miwa-cho, those in the early successional stage were few in number and small in patch size. Several woody plants covered under the pine canopy. The shade-tolerant shrub invaded into pine forest floor, because the undergrowth as a traditional energy source had no longer used. Pine forests were partly succeeded by deciduous oaks in Miwa-cho corresponding to the social changes. On the contrary in Yanghwa-ri, the vegetation replacement will not present because traditional management such as collecting fuels and making graveyards will be remained as a Korean ideology in the rural landscape.     

Comparative analysis of complete orthologous centromeres from two subspecies of rice reveals rapid variation of centromere organization and structure

Centromeres are sites for assembly of the chromosomal structures that mediate faithful segregation at mitosis and meiosis. This function is conserved across species, but the DNA components that are involved in kinetochore formation differ greatly, even between closely related species. To shed light on the nature, evolutionary timing and evolutionary dynamics of rice centromeres, we decoded a 2.25‐Mb DNA sequence covering the centromeric region of chromosome 8 of an indica rice variety, ‘Kasalath’ (Kas‐Cen8). Analysis of repetitive sequences in Kas‐Cen8 led to the identification of 222 long terminal repeat (LTR)‐retrotransposon elements and 584 CentO satellite monomers, which account for 59.2% of the region. A comparison of the Kas‐Cen8 sequence with that of japonica rice ‘Nipponbare’ (Nip‐Cen8) revealed that about 66.8% of the Kas‐Cen8 sequence was collinear with that of Nip‐Cen8. Although the 27 putative genes are conserved between the two subspecies, only 55.4% of the total LTR‐retrotransposon elements in ‘Kasalath’ had orthologs in ‘Nipponbare’, thus reflecting recent proliferation of a considerable number of LTR‐retrotransposons since the divergence of two rice subspecies of indica and japonica within Oryza sativa. Comparative analysis of the subfamilies, time of insertion, and organization patterns of inserted LTR‐retrotransposons between the two Cen8 regions revealed variations between ‘Kasalath’ and ‘Nipponbare’ in the preferential accumulation of CRR elements, and the expansion of CentO satellite repeats within the core domain of Cen8. Together, the results provide insights into the recent proliferation of LTR‐retrotransposons, and the rapid expansion of CentO satellite repeats, underlying the dynamic variation and plasticity of plant centromeres.     

High‐mobility group box 1 from reactive astrocytes enhances the accumulation of endothelial progenitor cells in damaged white matter

High‐mobility group box 1 (HMGB1) was initially described as a damage‐associated‐molecular‐pattern (DAMP) mediator that worsens acute brain injury after stroke. But, recent findings suggest that HMGB1 can play a surprisingly beneficial role during stroke recovery by promoting endothelial progenitor cell (EPC) function and vascular remodeling in cortical gray matter. Here, we ask whether HMGB1 may also influence EPC responses in white matter injury. The standard lysophosphatidylcholine (LPC) injection model was used to induce focal demyelination in the corpus callosum of mice. Immunostaining showed that within the focal white matter lesions, HMGB1 was up‐regulated in GFAP‐positive reactive astrocytes, along with the accumulation of Flk1/CD34‐double‐positive EPCs that expressed pro‐recovery mediators such as brain‐derived neurotrophic factor and basic fibroblast growth factor. Astrocyte–EPC signaling required the HMGB1 receptor RAGE as treatment with RAGE‐neutralizing antibody significantly decreased EPC accumulation. Moreover, suppression of HMGB1 with siRNA in vivo significantly decreased EPC numbers in damaged white matter as well as proliferated endothelial cell numbers. Finally, in vitro cell culture systems confirmed that HMGB1 directly affected EPC function such as migration and tube formation. Taken together, our findings suggest that HMGB1 from reactive astrocytes may attract EPCs to promote recovery after white matter injury.     

Optogenetically Induced Seizure and the Longitudinal Hippocampal Network Dynamics

Epileptic seizure is a paroxysmal and self-limited phenomenon characterized by abnormal hypersynchrony of a large population of neurons. However, our current understanding of seizure dynamics is still limited. Here we propose a novel in vivo model of seizure-like afterdischarges using optogenetics, and report on investigation of directional network dynamics during seizure along the septo-temporal (ST) axis of hippocampus. Repetitive pulse photostimulation was applied to the rodent hippocampus, in which channelrhodopsin-2 (ChR2) was expressed, under simultaneous recording of local field potentials (LFPs). Seizure-like afterdischarges were successfully induced after the stimulation in both W-TChR2V4 transgenic (ChR2V-TG) rats and in wild type rats transfected with adeno-associated virus (AAV) vectors carrying ChR2. Pulse frequency at 10 and 20 Hz, and a 0.05 duty ratio were optimal for afterdischarge induction. Immunohistochemical c-Fos staining after a single induced afterdischarge confirmed neuronal activation of the entire hippocampus. LFPs were recorded during seizure-like afterdischarges with a multi-contact array electrode inserted along the ST axis of hippocampus. Granger causality analysis of the LFPs showed a bidirectional but asymmetric increase in signal flow along the ST direction. State space presentation of the causality and coherence revealed three discrete states of the seizure-like afterdischarge phenomenon: 1) resting state; 2) afterdischarge initiation with moderate coherence and dominant septal-to-temporal causality; and 3) afterdischarge termination with increased coherence and dominant temporal-to-septal causality. A novel in vivo model of seizure-like afterdischarge was developed using optogenetics, which was advantageous in its reproducibility and artifact-free electrophysiological observations. Our results provide additional evidence for the potential role of hippocampal septo-temporal interactions in seizure dynamics in vivo. Bidirectional networks work hierarchically along the ST hippocampus in the genesis and termination of epileptic seizures.     

Distribution of prosaposin in the rat nervous system

Prosaposin is the precursor of four sphingolipid activator proteins (saposins A, B, C, and D) for lysosomal hydrolases and is abundant in the nervous system and muscle. In addition to its role as a precursor of saposins in lysosomes, intact prosaposin has neurotrophic effects in vivo or in vitro when supplied exogenously. We examined the distribution of prosaposin in the central and peripheral nervous systems and its intracellular distribution. Using a monospecific antisaposin D antibody that crossreacts with prosaposin but not with saposins A, B, or C, immunoblot experiments showed that both the central and peripheral nervous systems express unprocessed prosaposin and little saposin D. Using the antisaposin D antibodies, we demonstrated that prosaposin is abundant in almost all neurons of both the central and peripheral nervous systems, including autonomic nerves, as well as motor and sensory nerves. Immunoelectron microscopy using double staining with antisaposin D and anticathepsin D antibodies showed strong prosaposin immunoreactivity mainly in the lysosomal granules in the neurons in both the central and peripheral nervous systems. The expression of prosaposin mRNA, examined using in situ hybridization, was observed in these same neurons. Our results suggest that prosaposin is synthesized ubiquitously in neurons of both the central and peripheral nervous systems. Funding: This study was supported by the Ehime University INCS and in part by grants-in-aid for Scientific Research to S.M. (Exploratory Res. 19659380) from the Japan Society for the Promotion of Science and to AS (Priority Areas 18023029) from the Ministry of Education, Culture, Sports, Science and Technology of Japan.     

Regeneration of horseradish hairy roots incited by Agrobacterium rhizogenes infection

Surface-sterilized leaf disks of horse-radish (Armoracia lapathifolia) were immersed in a suspension of Agrobacterium rhizogenes harboring the root-inducing plasmid (pRi) and cultured on a solid medium. Within about 10 days after inoculation, adventitious roots (hairy roots) emerged from the leaf disks. No roots emerged from the uninoculated leaf disks. The excised hairy roots grew vigorously in the dark and exhibited extensive lateral branches in the absence of phytohormones. When the hairy roots were moved into the light, numerous adventitious buds thrust out of the roots within about 10 days, and they developed into complete plants (R0 generation). R0 plants revealed leaf wrinkle. Root masses of cultured R0 plants were of two types. One had fibrous roots only and the other had both fibrous and tuberous roots Leaf disks of the R0 plants proliferated adventitious roots (R1 generation) on a solid medium after 1–2 weeks of culture. Phenotypical characters of the R1 roots were the same as those observed with the initial hairy roots. The T-DNA sequences of pRi were detected within DNA isolated from the hairy roots and their regenerants.     

Grid map analysis and its application for detecting vegetation changes in Japan

Abstract. Grid maps are used as a basic vegetation data base in Japan; they are simplified from vector-based vegetation maps. We estimated the frequency error or lack of information corresponding to reduced resolution and examined the reliable limits of this data base. We produced 10 grid maps on five different scales from 50 m to 1000 m using two different methods using both the whole cell (W-method) and only the central circle (C-method) from a vegetation map at scale 1: 25 000. We found that patches larger than the area of a cell on a vector-based map could be kept almost certainly on any map, but many patches of less than the cell size were lost. The number of missing patches with the C-method is fewer at every scale than those with the W-method. Though the value of Morisita's Cλ (p) index showed that the similarity with the original map was high - from the 50-m to the 200-m resolution - it was increasingly lower on the 400-m and 1000-m grid maps. The values of the Shannon index on the original map, 50-m and 100-m grid maps were not different, but they decreased from the 200-m to 1000-m grid maps. Because the vegetation data base of the Japanese Environment Agency used a 1000-m C-method grid map, we found that much information on patches less than 100 ha had disappeared. Information about dominant vegetation or large patches is almost accurate in this data base.     

Microsatellite analysis of pollen flow in Rhododendron metternichii var. hondoense

Microsatellite analysis was used to characterize the patterns of pollen flow in a 150 m × 70 m quadrat containing 18 flowering trees of Rhododendron metternichii Sieb. et Zucc. var. hondoense Nakai. Using six microsatellite genetic markers and exclusion analysis, we determined the paternal trees of 216 seedlings germinated from five fruits produced by four adults. Each fruit was pollinated by a small number of largely adjacent trees, but 20–30% of pollen came from outside the quadrat. Adult trees that produced many flowers had a high self-pollination rate. A directional flow of pollen from late-blooming trees to early ones was observed.