ALBERT

Description: :Background: Chromatin structure is implicated in regulating gene transcription in stressresponse. Transcription factors, transferases, and deacetylases, such as Msn2, Set1, and Snf1,have been identified as key regulators in stress response. Here, we reported the dynamics ofnucleosome occupancy, Htz1 deposition, and histone H3 lysine 4 dimethylation (H3K4me2)and histone H3 lysine 79 trimethylation (H3K79me3) in Saccharomyces cerevisiae underoleate stress.Results: Our results indicated that citrate cycle-associated genes are enhanced and ribosomegenes are repressed during the glucose-oleate shift. Importantly, Htz1 acts as a sensor foroleate stress. High-throughput ChIP-chip analysis showed that Htz1 has redistributed acrossthe genome during oleate stress. The number of Htz1-bound genes increases with stress, andthe number of Htz1-bound ribosome genes decreases with stress. The dynamics of Htz1 andH3K79me3 around transcription factor-binding sites correlate with transcriptional changes.Moreover, we found that nucleosome dynamics are coupled with Htz1 binding changes uponstress. In unstressed conditions (2% glucose), nucleosome occupancy is comparable betweenHtz1-bound genes and Htz1-depleted genes; in stressed conditions (0.2% oleate for 8 hours),the nucleosome occupancy of Htz1-depleted genes is significantly lower than that ofHtz1-bound genes. We also found that Msn2 acts an important role in response to the oleatestress and Htz1 is dynamic in Msn2-target genes.Conclusions: Htz1 senses the oleate stress and undergoes a global redistribution, and thischange couples dynamics of nucleosome occupancy. Our analysis suggests that Htz1 andnucleosome dynamics change in response to oleate stress.

Description: Hydrologic viability, in terms of moisture availability, is fundamental to ecosystem sustainability in arid and semi-arid regions. In this study, we examine the spatial distribution and after-planting variations of soil moisture content (SMC) in black locust tree (Robinia pseudoacacia L.) plantings in the Loess Plateau of China at a regional scale. Thirty sites (5 to 45 yr old) were selected, spanning an area of 300 km by 190 km in the northern region of the Shaanxi Province. The SMC was measured to a depth of 100 cm at intervals of 10 cm. Geographical, topographic and vegetation information was recorded, and soil organic matter was evaluated. The results show that, at the regional scale, SMC spatial variability was most highly correlated with rainfall. The negative relationship between the SMC at a depth of 20–50 cm and the stand age was stronger than at other depths, although this relationship was not significant at a 5 % level. Watershed analysis shows that the after-planting SMC variation differed depending upon precipitation. The SMC of plantings in areas receiving sufficient precipitation (e.g., mean annual precipitation (MAP) of 617 mm) may increase with stand age due to improvements in soil water-holding capacity and water-retention abilities after planting. For areas experiencing water shortages (e.g., MAP = 509 mm), evapotranspiration may cause planting soils to dry within the first 20 yr of growth. It is expected that, as arid and semi-arid plantings age, evapotranspiration will decrease, and the soil profile may gradually recover. In extremely dry areas (e.g., MAP = 352 mm), the variation in after-planting SMC with stand age was found to be negligible. The MAP can be used as an index to divide the study area into different ecological regions. Afforestation may sequentially exert positive, negative and negligible effects on SMCs with a decrease in the MAP. Therefore, future restoration measures should correspond to the local climate conditions, and the MAP should be a major consideration for the Loess Plateau. Large-scale and long-term research on the effects of restoration projects on SMCs is needed to support more effective restoration policies. The interaction between afforestation and local environmental conditions, particularly water availability to plants, should be taken into account in afforestation campaigns in arid and semi-arid areas.

Description: Hydrologic viability in terms of moisture availability is fundamental for ecosystem sustainability in arid and semiarid regions. This study was conducted to examine the regional scale and after-planting variations of soil moisture for planted Black Locust tree (Robinia pseudoacacia L.) plantations in the Loess Plateau of China. 30 sites spanning for 300 km long and 190 km wide in the Northern Shaanxi Province were selected in all. On the regional scale, SMC spatial variability was most closely correlated to rainfall. A large amount of herbaceous cover helped increase the moisture level in the topsoil (0–10 cm), and soil moisture in the deeper layer between 20 and 60 cm below the surface was mostly affected by plantations. The after planting SMC of artificial plantations in areas with sufficient precipitation (mean annual precipitation (MAP) 617 mm) may increase with stand age due to soil water-holding capacity and soil water retention ability improvements after planting. For areas in water shortage (MAP 509 mm), evapotranspiration caused the soil of the plantation to dry up in the first 20 years of growth. Then as the plantation aged, evapotranspiration decreased, and the soil profile recovered gradually. In areas where water was extremely lacking, soil moisture was too rare to be used by trees, and after-planting SMC variation with stand age was insignificant. For the sustainability of artificial ecosystem, the construction of artificial plantations needs to be thoroughly evaluated on regional scale based on the climate conditions (especially rainfall) and soil moisture conditions in arid and semiarid areas.