A simple and precise aberrant translocation of the rat c-myc gene into the epsilon-heavy chain switch region of the IgE-producing immunocytoma, IR162

We report a simple type of reciprocal chromosomal translocation in the LOU rat IgE-secreting immunocytoma cell line, IR162, involving the c-myc protooncogene and the switch region of the epsilon immunoglobulin heavy chain, c-myc/S epsilon. By cloning and sequencing the translocation-associated and the homologous normal c-myc and S epsilon DNAs, we have identified the position of the translocational junction in both the c-myc 5'-flanking region and the repetitive elements of the S epsilon region. The translocational recombination was precise, and no insertion or N-addition was found in the junctional region, leaving all the c-myc exons, together with two promoter sites, intact. RNase mapping confirmed that the same promoters were utilized in IR162 and normal LOU spleen cells. No point mutation was found in the 5'-flanking region and the 3'-portion of exon 1 of the translocated c-myc gene. However, the putative silencer region was lost with the translocation. It was also noticed that a strikingly AT-rich sequence associated with S epsilon region had translocated to the 5'-flanking region of c-myc gene. We discuss the possibility that a change of DNA topology, perhaps either due to the juxtaposition of an AT-rich sequence of the S epsilon region, or to the loss of the putative silencer element, may contribute to c-myc gene deregulation in IR162.     

Responses of Crop Water Use Efficiency to Climate Change and Agronomic Measures in the Semiarid Area of Northern China

It has long been concerned how crop water use efficiency (WUE) responds to climate change. Most of existing researches have emphasized the impact of single climate factor but have paid less attention to the effect of developed agronomic measures on crop WUE. Based on the long-term field observations/experiments data, we investigated the changing responses of crop WUE to climate variables (temperature and precipitation) and agronomic practices (fertilization and cropping patterns) in the semi-arid area of northern China (SAC) during two periods, 1983–1999 and 2000–2010 (drier and warmer). Our results suggest that crop WUE was an intrinsical system sensitive to climate change and agronomic measures. Crops tend to reach the maximum WUE (WUEmax) in warm-dry environment while reach the stable minimum WUE (WUEmin) in warm-wet environment, with a difference between WUEmax and WUEmin ranging from 29.0%-55.5%. Changes in temperature and precipitation in the past three decades jointly enhanced crop WUE by 8.1%-30.6%. Elevated fertilizer and rotation cropping would increase crop WUE by 5.6–11.0% and 19.5–92.9%, respectively. These results indicate crop has the resilience by adjusting WUE, which is not only able to respond to subsequent periods of favorable water balance but also to tolerate the drought stress, and reasonable agronomic practices could enhance this resilience. However, this capacity would break down under impact of climate changes and unconscionable agronomic practices (e.g. excessive N/P/K fertilizer or traditional continuous cropping). Based on the findings in this study, a conceptual crop WUE model is constructed to indicate the threshold of crop resilience, which could help the farmer develop appropriate strategies in adapting the adverse impacts of climate warming.     

Mitochondrial ribosomal protein S9M is involved in male gametogenesis and seed development in Arabidopsis

• Mitochondrial function is critical for cell vitality in all eukaryotes including plants. Although plant mitochondria contain many proteins, few have been studied in the context of plant development and physiology.
• We used knock‐down mutant RPS9M to study its important role in male gametogenesis and seed development in Arabidopsis thaliana.
• Knock‐down of RPS9M in the rps9m‐3 mutant led to abnormal pollen development and impaired pollen tube growth. In addition, both embryo and endosperm development were affected. Phenotype analysis revealed that the rps9m‐3 mutant contained a lower amount of endosperm and nuclear proteins, and both embryo cell division and embryo pattern were affected, resulting in an abnormal and defective embryo. Lowering the level of RPS9M in rps9m‐3 affects mitochondrial ribosome biogenesis, energy metabolism and production of ROS.
• Our data revealed that RPS9M plays important roles in normal gametophyte development and seed formation, possibly by sustaining mitochondrial function.

     

Negative regulation of AMPK signaling by high glucose via E3 ubiquitin ligase MG53

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Proliferation of myofibroblasts in the stroma of renal oncocytoma

Objectives: Myofibroblasts are a vital component of stroma of many malignant neoplasms, but it is not yet established whether stromal myofibroblasts also exist in benign tumours such as oncocytoma of the kidney. Materials and methods: Histomorphological and immunohistochemical analysis of 16 renal oncocytomas diagnosed at Chang Gung Memorial Hospital, Taiwan, has been performed. Results: Renal oncocytomas were composed of oncocytes, large cells with granular eosinophilic cytoplasm, arranged mostly in sheets, in tubulocystic or combined pattern. Few oncocytes appeared to be undergoing proliferation or apoptosis. MIB‐1 and active caspase 3 indices were low, but higher in tumour than in surrounding non‐tumour parenchyma (MIB‐1: 0.93 ± 0.09 versus 0.46 ± 0.07, P < 0.001 and active caspase 3: 0.76 ± 0.08 versus 0.41 ± 0.09, P < 0.001). Wnt/β‐catenin signalling was not implicated in this neoplasm, as there was no loss of E‐cadherin membranous localization or expression of intranuclear β‐catenin in the cells. Clumps of oncocytes were stained with periodic acid Schiff and had collagen I‐, collagen III‐ and fibronectin‐positive, but desmin‐ and human caldesmon‐negative stromas. Importantly, α‐smooth muscle actin (SMA)‐immunostaining established the myofibroblastic nature of many of the stromal cells. Some of the myofibroblasts were also positive for MIB‐1, indicating a proliferative role for them in the stroma. Conclusions: Renal oncocytomas were composed of two independent compartments: benign oncocytes and pronounced fibrotic stroma, which consisted of proliferating myofibroblasts (SMA‐ and MIB‐1‐positive) which were associated with excessive deposition of extracellular matrix (periodic acid Schiff‐component, collagen I‐, collagen III‐ and fibronectin‐positive, and desmin‐ and human caldesmon‐negative).