温帯の散孔材樹種における道管サイズの季節変化と水分条件との関係

Vessel lumen area and leaf water potential (ψleaf) at predawn and midday were measured periodically to reveal seasonal variations in the vessel sizes of diffuse-porous species and to determine the factors that cause this variation. Two deciduous species (Cercidiphyllum japonicum and Liriodendron tulipifera) and one evergreen species (Quercus glauca) were studied. In most of the samples, mean vessel lumen area (MVLA) initially increased then eventually decreased after a period, but this period varied among species. In C. japonicum, the decrease in MVLA coincided with a decrease in predawn ψleaf. In contrast, MVLA variations in most samples of L. tulipifera and Q. glauca did not show such a relationship. However, one of the L. tulipifera samples had an earlier decrease in MVLA that coincided with a lower predawn ψleaf. There was no clear relationship between the variation in vessel size and midday ψleaf, because midday ψleaf showed daily variation depending on vapor pressure deficit, which had less seasonality. Thus, we concluded that there are species-specific annual patterns in vessel size variation that are likely determined by internal factors. Low water availability is one of the external factors inducing the formation of narrower vessels.散孔材における道管サイズの季節変化, およびその変化を引き起こす要因を明らかにするため, 道管形成の観察と夜明け前と日中の葉の水ポテンシャル (ψleaf)の測定を定期的に行った. 試料には落葉樹のカツラとユリノキ, 常緑樹のアラカシを用いた. 全ての樹種で道管サイズは一年の成長の始めに増加し, ある時期から減少していた. 減少が始まる時期は樹種によって異なっており, カツラでは夜明け前のψleaf の低下と対応が見られた. 一方でユリノキとアラカシでは, 道管サイズと夜明け前のψleaf の対応は見られなかった. ただし夜明け前のψleaf が他よりも低下していた個体では道管サイズの減少が早く始まっていたため, 乾燥ストレスの影響が示唆された. 日中のψleaf は日変動が大きく, 道管サイズとの明確な関連性は見られなかった. したがって, 年輪内の道管サイズの変化は主に内的要因によって決まっており, 乾燥ストレスは外部要因として道管サイズを減少させると考えられた

Relationship between the timing of vessel formation and leaf phenology in ten ring-porous and diffuse-porous deciduous tree species

The goal of this study is to clarify how different aspects of plant function are coordinated developmentally for species of ring-porous versus diffuse-porous deciduous trees, comparing the timing of leaf phenology and vessel formation in twigs and stems from an ecophysiological viewpoint. Cylindrical stem cores and twigs were collected at intervals from early spring through summer from five ring-porous and five diffuse-porous species in a cool temperate forest, and leaf and vessel formation were observed simultaneously. We found that the first-formed vessels of the year were lignified in twigs around the time of leaf appearance and at or before full leaf expansion of each tree in both groups of species with flush-leaves. Vessels in stems were lignified 2 weeks before to 4 weeks after leaf appearance and before or around full leaf expansion of the tree in ring-porous species. This was significantly earlier than in diffuse-porous species, in which stem vessel lignification was 2–8 weeks after leaf appearance and at or after full leaf expansion of the tree. The timing of vessel formation in twigs compared to stems was significantly earlier in ring-porous species than in diffuse-porous species. Lignification of vessels in stems occurred within 2 weeks of lignification in the twigs of ring-porous species and 2–8 weeks after lignification in twigs of diffuse-porous species. These results indicate the order and time-lag of leaf and vessel formation. Ring-porous species showed intensive leaf/vessel production, whereas diffuse-porous species showed less intensive leaf/vessel production

成長錐を用いた木片試料採取法の検討 : 道管形成の季節変化を調べる観点から

Feature : Impact on Ashiu forest ecosystem due to dee

LAMC2 promotes gemcitabine resistance in PDAC

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease with poor prognosis. Gemcitabine remains an effective option for the majority of PDAC patients. Unfortunately, currently no reliable prognostic and predictive biomarkers of therapeutic response are available for the patients with PDAC. Laminin γ2 (LAMC2) is overexpressed in several cancers, and its high expression facilitates cancer development and chemoresistance. However, its functional role in PDAC remains unclear, and a better understanding of this will likely help improve the prognosis of PDAC patients. This study aimed to elucidate the clinical and biological role of LAMC2 in PDAC. We first analyzed the expression levels of LAMC2 by real-time reverse transcription PCR in a cohort of 114 PDAC patients. Interestingly, higher expression of LAMC2 significantly correlated with poor survival in PDAC cohort. In addition, elevated LAMC2 expression served as a potential prognostic marker for survival. Subsequently, functional characterization for the role of LAMC2 in PDAC was performed by small interfering RNA (siRNA) knockdown in pancreatic cancer (PC) cell lines. Interestingly, inhibition of LAMC2 in PC cells enhanced the gemcitabine sensitivity and induction of apoptosis. Moreover, it inhibited colony formation ability, migration, and invasion potential. Furthermore, LAMC2 regulated the expression of epithelial-mesenchymal transition (EMT) phenotype. In addition, LAMC2 significantly correlated with genes associated with the expression of ATP-binding cassette (ABC) transporters in PC cells and PDAC patients. In conclusion, these results suggest that LAMC2 regulates gemcitabine sensitivity through EMT and ABC transporters in PDAC and may be a novel therapeutic target in PDAC patients

Radial and vertical distributions of radiocesium in tree stems of Pinus densiflora and Quercus serrata 1.5 y after the Fukushima nuclear disaster.

The radial and vertical distributions of radiocesium in tree stems were investigated to understand radiocesium transfer to trees at an early stage of massive contamination from the Fukushima nuclear disaster. A conifer species (Japanese red pine) and a broad-leaved species (Japanese konara oak) were selected to determine whether the radiocesium contamination pattern differs between species. Stem disks were collected at several heights and separated into outer bark, inner bark, and wood. The radiocesium concentration was the highest in the outer bark, followed by that in the inner bark and wood. The vertical distribution of the radiocesium concentration at each stem part differed between the species. The difference between species in radiocesium concentration of the outer bark could be explained by presence or absence of leaves at the time of the disaster. However, the reasons for the differences between species in the radiocesium concentration of the inner bark and wood are unclear. The radial distribution in the wood of the studied species showed a common pattern across stem disk heights and species. However, the radiocesium concentration ratio between sapwood and inner bark was significantly different between species. Although the radial contamination pattern in the wood was similar in the studied species during the early stage of contamination, the radiocesium transport pathway and allocation would be different between the species, and the contamination pattern will likely be different between the species at later stages. Continued investigations are important for understanding the radiocesium cycle and the accumulation of radiocesium in the tree stems of each species