Auxin is a key regulator of plant growth and development. Within the root tip, auxin distribution plays a crucial role specifying developmental zones and coordinating tropic responses. Determining how the organ-scale auxin pattern is regulated at the cellular scale is essential to understanding how these processes are controlled. In this study, we developed an auxin transport model based on actual root cell geometries and carrier subcellular localizations. We tested model predictions using the DII-VENUS auxin sensor in conjunction with state-of-the-art segmentation tools. Our study revealed that auxin efflux carriers alone cannot create the pattern of auxin distribution at the root tip and that AUX1/LAX influx carriers are also required. We observed that AUX1 in lateral root cap (LRC) and elongating epidermal cells greatly enhance auxin’s shootward flux, with this flux being predominantly through the LRC, entering the epidermal cells only as they enter the elongation zone. We conclude that the nonpolar AUX1/LAX influx carriers control which tissues have high auxin levels, whereas the polar PIN carriers control the direction of auxin transport within these tissues. 相似文献
Efficient isolation of target DNA is a crucial first step of DNA-based metagenomic analyses of environmental samples. Insufficient quantity and purity of DNA isolated using commercial kits result in missing genetic information, especially for large-diameter substrates in constructed wetlands (CWs). Here, we addressed this problem by devising a cost-effective calcium chloride lysozyme-sodium dodecyl sulfate (SDS) method (CCLS), with key improvements in the steps of humic acid removal and cell lysis. The buffer comprising Tris, EDTA, Na2O2P7 and PVPP (TENP), and skim milk, could reduce adsorption between microorganisms and substrates, and calcium chloride precipitated and removed over 94% of humic acid. This humic acid removal step, when compared to the PowerSoil DNA kit (MO BIO Laboratories Inc.) (MBKIT), significantly enhanced the DNA purity (A260/230) from 0.68 to 1.63 (p < 0.01). When gentle and extended cell lysis in CCLS replaced the short but violent bead-beating in the MBKIT, DNA yield and the amount of lysed bacteria detected by quantitative real-time polymerase chain reaction (qPCR) on average increased by 2 and 4 folds, respectively, compared to that obtained using the MBKIT (p < 0.01). Furthermore, the full-length bacterial 16S rRNA gene and nirK gene from denitrifying microorganisms were successfully amplified from CCLS-generated DNA. Additionally, bacterial diversity indices of richness, Shannon, and evenness examined by denaturing gradient gel electrophoresis (DGGE) increased by 75, 30, and 7%, respectively, by CCLS compared to that using the MBKIT. Hence, the CCLS method enables improved evaluation of microbial density and diversity in CW systems.
Responses of plants exposed to drought and rewatering have been well documented; however, little is known concerning strategies of psammophyte to drought and rewatering under different soil nutrient regimes. For this study, Pennisetum centrasiaticum under two soil nutrient regimes was subjected to progressive drought and subsequent rewatering. Soil water status, gas exchange characteristics, chlorophyll a fluorescence characteristics as well as biomass traits were measured to investigate ecophysiological responses. Net photosynthesis rate (Pn), stomatal conductance (gs), water use efficiency, maximum quantum efficiency of photosynthesis system II (PSII, FV/FM), electron transport flux per cross section (ET0/CS0), and performance index on cross section basis (PICS) were suppressed during drought periods for both nutrient regimes. Meanwhile, leaf intercellular CO2 concentration (Ci), minimal fluorescence intensity (F0), and dissipated energy flux per cross section (DI0/CS0) increased. Reversible downregulation of PSII photochemistry and enhanced thermal dissipation of excess excitation energy (DI0/CS0) contributed to enhanced photo-protection in drought-stressed plants. Thus, the results indicate that P. centrasiaticum is capable of withstanding and surviving extreme drought events, and the recovery pattern of stressed P. centrasiaticum under both nutrient regimes was similar. However, fertilization increased the biomass and the variation in gas exchange and chlorophyll a fluorescence characteristics during drought periods. Additionally, fertilization accelerated the process of drought and aggravated stress under extreme drought events. Thus, the fertilization strategy used in P. centrasiaticum restoration should be carefully selected—fertilization may not always be beneficial. 相似文献
Fatty acyl thioesterases control the termination of intraplastidial fatty acid synthesis by hydrolyzing fatty acyl-ACP complexes. The fatty acyl thioesterase A (FATA) gene family in Arabidopsis comprises two members, i.e., FATA1 and FATA2. Previous studies have shown that FATAs display high specificity for unsaturated fatty acids. However, the expression pattern and individual roles of these two FATA genes remains unknown. In this study, we initially studied the expression patterns of FATA1 and FATA2 in various organs of Arabidopsis and we found that FATA1 was expressed at low level in all organs examined and FATA2 was detected in all organs examined, with especially high accumulation in siliques. The transient expression of a FATA2-eGFP fusion in Arabidopsis green leaf protoplasts showed that FATA2 was localized in chloroplasts. A T-DNA insertion mutant line of FATA2 (named fata2) was obtained and used for phenotypic observation. Semiquantitative RT-PCR assay showed that the expression level of FATA2 decreased significantly in fata2 compared with that in wild type. Furthermore, fata2 mutants produced longer siliques with more seeds, whereas seed size was slightly smaller than that of wild type. Compositional analysis of seed oil revealed that, except for a subtly decreased C24:0 and unchanged C22:0 level, all other fatty acids were increased by between 10 and 60 % in fata2 dry seeds compared with those in wild-type. Taken together, our results indicate that FATA2 plays important roles in lipid metabolism in seeds and in silique development in Arabidopsis thaliana. 相似文献
The purpose of this study was to determine the functional recovery of the transplanted induced pluripotent stem cells in a rat model of Huntington''s disease with use of 18F-FDG microPET/CT imaging.
Methods
In a quinolinic acid-induced rat model of striatal degeneration, induced pluripotent stem cells were transplanted into the ipsilateral lateral ventricle ten days after the quinolinic acid injection. The response to the treatment was evaluated by serial 18F-FDG PET/CT scans and Morris water maze test. Histological analyses and Western blotting were performed six weeks after stem cell transplantation.
Results
After induced pluripotent stem cells transplantation, higher 18F-FDG accumulation in the injured striatum was observed during the 4 to 6-weeks period compared with the quinolinic acid-injected group, suggesting the metabolic recovery of injured striatum. The induced pluripotent stem cells transplantation improved learning and memory function (and striatal atrophy) of the rat in six week in the comparison with the quinolinic acid-treated controls. In addition, immunohistochemical analysis demonstrated that transplanted stem cells survived and migrated into the lesioned area in striatum, and most of the stem cells expressed protein markers of neurons and glial cells.
Conclusion
Our findings show that induced pluripotent stem cells can survive, differentiate to functional neurons and improve partial striatal function and metabolism after implantation in a rat Huntington''s disease model. 相似文献
The regulatory activities of mouse CD4+Foxp3+ T cells on various immune cells, including NK cells, have been well documented. Under some conditions, conventional CD4+Foxp3− T cells in the periphery are able to acquire inhibitory function on other T cells, but their roles in controlling innate immune cells are poorly defined. As a potential cellular therapy for cancer, ex vivo activated CD4+Foxp3− effector T cells are often infused back in vivo to suppress tumor growth and metastasis. Whether such activated T cells could affect NK-cell control of tumorigenesis is unclear. In the present study, we found that mitogen-activated CD4+Foxp3− T cells exhibited potent suppressor function on NK-cell proliferation and cytotoxicity in vitro, and notably facilitated B16 melanoma metastasis in vivo. Suppression of NK cells by activated CD4+Foxp3− T cells is cell-cell contact dependent and is mediated by Qa-1:NKG2A interaction, as administration of antibodies blocking either Qa-1 or NKG2A could completely reverse this suppression, and significantly inhibited otherwise facilitated melanoma metastasis. Moreover, activated CD4+Foxp3− cells from Qa-1 knockout mice completely lost the suppressor activity on NK cells, and failed to facilitate melanoma metastasis when transferred in vivo. Taken together, our findings indicate that innate anti-tumor response is counter regulated by the activation of adaptive immunity, a phenomenon we term as “activation-induced inhibition”. Thus, the regulatory role of activated CD4+Foxp3− T cells in NK-cell activity must be taken into consideration in the future design of cancer therapies. 相似文献