Methionine Metabolism Regulates Maintenance and Differentiation of Human Pluripotent Stem Cells

SummaryMouse embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) are in a high-flux metabolic state, with a high dependence on threonine catabolism. However, little is known regarding amino acid metabolism in human ESCs/iPSCs. We show that human ESCs/iPSCs require high amounts of methionine (Met) and express high levels of enzymes involved in Met metabolism. Met deprivation results in a rapid decrease in intracellular S-adenosylmethionine (SAM), triggering the activation of p53-p38 signaling, reducing NANOG expression, and poising human iPSC/ESCs for differentiation, follow by potentiated differentiation into all three germ layers. However, when exposed to prolonged Met deprivation, the cells undergo apoptosis. We also show that human ESCs/iPSCs have regulatory systems to maintain constant intracellular Met and SAM levels. Our findings show that SAM is a key regulator for maintaining undifferentiated pluripotent stem cells and regulating their differentiation

Novel anti‐tumor mechanism of galanin receptor type 2 in head and neck squamous cell carcinoma cells

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/102710/1/cas12315.pd

A model relating transpiration for Japanese cedar and cypress plantations with stand structure

Previous studies have revealed that changes in forest structure due to management (e.g., thinning, aging, and clearcutting) could affect the forest water balance. However, there are unexplained variability in changes in the annual water balance with changing structure among different sites. This is the case even when analyzing data for specific species/regions. For a more advanced and process-based understanding of changes in the water balance with changing forest structure, we examined transpiration (E) observed using the sap-flux method for 14 Japanese cedar and cypress plantations with various structure (e.g., stem density and diameter) in Japan and surrounding areas and developed a model relating E with structural parameters. We expressed E using the simplified Penman–Monteith equation and modeled canopy conductance (G[c]) as a product of reference G[c] (G[cref]) when vapor pressure deficit is 1.0 kPa and functions expressing the responses of G[c] to meteorological factors. We determined G[cref] and parameters of the functions for the sites separately. E observed for the 14 sites was not reproduced well by the model when using mean values of G[cref] and the parameters among the sites. However, E observed for the sites was reproduced well when using G[cref] determined for each site and mean values of the parameters of the functions among the sites, similar to the case when using G[cref] and the parameters of the functions determined for each site. These results suggest that considering variations in G[cref] among the sites was important to reproduce variations in E, but considering variations in the parameters of the functions was not. Our analysis revealed that G[cref] linearly related with the sapwood area on a stand scale (A) and that Alinearly related with stem density (N) and powers of the mean stem diameter (d[m]). Thus, we proposed a model relating E with A (or N and d[m]), where G[cref] was calculated from A (or N and d[m]) and the parameters of the functions were assumed to be the mean values among the sites. This model estimates changes in Ewith changing structure from commonly available data (N and d[m]), and therefore helps improve our understanding of the underlying processes of the changes in the water balance for Japanese cedar and cypress plantations

Application of gene expression analyses to studies of general flowering

General flowering is a community-level mass flowering observed at irregular intervals of less than one year to 10 years in South-East Asian tropical rainforests. Several hypotheses have been proposed to explain the mechanism of general flowering, but it is still not clear how many triggers can induce general flowering and whether sensitivities to the trigger(s) are variable in different populations. To answer these questions, we review a method integrating gene expression data into environmental and endogenous data. Our study suggests that the function of the FLOWERING LOCUS T (FT) gene is conserved as a floral activator in dipterocarps, which makes it possible to detect the precise timing of flower induction from the expression of the FT homologues in dipterocarps. Combined with the environmental and endogenous data during flower induction, this method has the potential to become a powerful tool to identify the trigger(s) of general flowering. We also discuss the future application of this method to well-planned seed collection strategies for forest restoration

Dependance of isoprene emission flux on leaf mass per area of Phyllostachys pubescens (moso bamboo)

It is challenging to estimate isoprene emissions from plants and determine the basal isoprene emission rate (i.e., isoprene emission capacity under a specific light and leaf temperature) of plant species. Previous studies have investigated the effect of physiological factors on isoprene emission capacity; however, the effect of leaf morphology on isoprene emission capacity has seldom been mentioned. This study aims to clarify the relationship between the basal isoprene emission rate and leaf mass per area (LMA) of a woody bamboo (Phyllostachys pubescens). Since there was no observation of isoprene emission from low-LMA leaves of P. pubescens, we conducted measurements on culms exhibiting lower LMA (27.5-47.9 g m⁻²). By observing leaf-scale isoprene emission flux under a specific incident light (1000 μmol m⁻² s⁻¹) and temperature (30 °C) to represent basal isoprene emission fluxes, we found a series of varied area-based isoprene emission rate among leaves (1.4-32.2 nmol m⁻² s⁻¹) and a strong correlation between area-based isoprene emission rate and LMA without any distinction between culms. A further comparison with other studies demonstrated that even for the culms that exhibited larger LMA and isoprene emission flux, a generally consistent pattern in the relation of area-isoprene emission flux and LMA could be found across these sites. This result suggests the importance of detecting LMA in the determination of the basal isoprene emission rate, which can improve the current emission estimation method

Effects of soil water decline on diurnal and seasonal variations in sap flux density for differently aged Japanese cypress (Chamaecyparis obtusa) trees

The effects of soil drought on transpiration are often neglected when predicting transpiration for forests in humid regions under the influence of the Asian monsoon. These effects have indeed been neglected for Japanese cypress, Chamaecyparis obtusa, a major plantation species in Japan and the surrounding area, probably because previous studies have reported no clear effects of soil drought on transpiration for Japanese cypress forests. However, a few studies have reported an apparent reduction in transpiration with soil drought for young Japanese cypress forests. It remains unclear whether such a reduction in transpiration is limited to young Japanese cypress forests or if it is not uncommon for mature Japanese cypress forests, which occupy a large area in Japan. To clarify this point, we conducted sap flux measurements in a year with soil drought on three differently aged Japanese cypress stands including mature (43 years old) and relatively young (23 and 26 years old) trees. In a diurnal time scale, a cross correlation analysis of sap flux density (Fd) and vapor pressure deficit (VPD) showed that the time lags between Fd and VPD were 1-3 h in dry soil conditions. These were larger than those of wet soil conditions (&lt;1 h) for all sample trees. Fd at a given VPD in dry soil conditions was smaller than that in wet soil conditions for all sample trees; a 28%–63% reduction in the rate of change in Fd was observed under dry soil conditions. Because our results were obtained when the non-exceedance probability of recorded monthly precipitation was 9%–18%, the results suggest the need to consider the effects of soil drought more extensively. Those effects should be considered for not only relatively young but also mature Japanese cypress when predicting diurnal and seasonal patterns of transpiration in years with soil drought, and when predicting inter-annual patterns of transpiration for Japanese cypress despite humid temperate climate. </p

Sapflow characteristics and climatic responses in three forest species in the semiarid Loess Plateau region of China

&nbsp;In the semiarid Loess Plateau region of China ecosystems are frequently affected by water shortages Late spring and early summer are periods when forest communities tend to suffer from soil drought To clarify the water-use strategies of the main species in this area the xylem sap flow of trees from three species in the field was monitored for three successive periods in summer using Granier-type thermal dissipation probes Vapor pressure deficit (VPD) solar radiation (R(s)) and soil moisture had varying influences on sap flux density (F(d)) in the species Normalized F(d) values could be fitted to VPD using an exponential saturation function but the fit was better with a derived variable of transpiration (VT) an integrated index calculated from VPD and Rs From differences in model coefficients the species were roughly divided into two types with contrasting drought sensitivity The exotic Robinia pseudoacacia was defined as drought-sensitive type It showed higher sapflow increases in response to rainfall suggesting a high water demand and high Influence of soil water conditions on transpiration This species showed relatively late stomatal response to increasing VPD The wide-peak pattern of diurnal sapflow course also suggests relatively low stomatal regulation in this species The drought-insensitive type consisted of the naturally dominant Quercus liaotungensis and an indigenous concomitant species Armeniaca sibirica in the forest The sap flow of these species was not very sensitive to changes in soil water conditions The results suggest that typical indigenous species can manage the water consumption conservatively under both drought and wet conditions Variations in water use strategies within indigenous species are also detected (C) 2010 Elsevier B V All rights reserve

Estimating water use of a black locust plantation by the thermal dissipation probe method in the semiarid region of Loess Plateau, China

Black locust (Robinia pseudoacacia) is a major reforestation species in the semiarid region in the Loess Plateau of China. There has been increasing concern about the sustainability of the plantations because of their possible high water-use. This study was, accordingly, undertaken to quantify the stand-scale water use of a middle-aged black locust plantation in the region. The thermal dissipation probe method was applied to 27 trees to measure sap flux densities in an experimental plot during the growing season of 2008. The monoculture stand has a basal area of 23.3 m(2) ha(-1) and a maximum plant area index (PAI) of 2.89. Sapwood areas were estimated by use of a regressive relationship with the diameter at breast height (DBH) for scaling up of stand transpiration. The results showed that DBH could be a good predictor of sapwood area of individual trees. The diurnal cycles of average sap flux densities differed among DBH classes. Daily transpiration can be predicted from mean daily daytime vapor pressure deficit (VPD(m)) using a fitted exponential saturation model. Model variables were different among seasons, probably owing to different soil water conditions and leaf phenology. By using the derived model for each month, stand canopy transpiration over the growing season was estimated to be 73.8 mm, with an average daily value of 0.41 mm day(-1) and a maximum of 0.89 mm day(-1). The relatively small estimates of stand transpiration might be attributed to low PAI and sap wood area of the middle-aged stand

Transpiration of a Cryptomeria japonica plantation in winter : analysis based on one-year sap flow measurements

Cryptomeria japonica plantations, a type of coniferous evergreen forest, are one of the most common forest types in Japan. It is critical to clarify the differences between the forest water cycle of C. japonica plantations and that of broad-leaved deciduous forests because as many C. japonica plantations in Japan have been converted from broad-leaved deciduous forests. This study examined the significance of the transpiration of a C. japonica plantation in winter using one-year heat pulse velocity (HPV) data. HPV would be linearly related to the canopy transpiration rate and was higher in summer than in winter, with a maximum in August. In January and February, March and April, and December, HPV was approximately 20, 70, and 40% of that in August, respectively. The relatively high HPV in March and April indicated that the forest water cycle of the C. japonica plantation during these months was quite different from that of broad-leaved deciduous forests in the same region in terms of transpiration常緑林であるスギ人工林は日本でもっとも一般的な森林タイプのひとつである。日本のスギ人工林の多くは落葉広葉樹林を伐採して作られたものであり，このような土地利用変化の影響を考えるうえで，スギ人工林と落葉広葉樹林の水循環の違いを明らかにすることは重要である。本研究では，スギ人工林における冬の蒸散量の大きさについて，通年計測されたヒートパルスデータを用いて検討した。林分蒸散量と対応するヒートパルス速度は，夏に大きく冬に小さかった。ヒートパルス速度の月間値は8月に最大となった。1・2月，3・4月，12月におけるヒートパルス速度の月間値は，それぞれ8月の20%，70%，40%だった。このように3・4月においてヒートパルス速度は比較的大きく，蒸散から見た場合，この時期のスギ人工林の水循環は同地域の落葉広葉樹林の水循環と大きく異なることが示され