Leaf senescence, which affects plant growth and yield in rice, is an ideal target for crop improvement and remarkable advances have been made to identify the mechanism underlying this process. We have characterized an early senile mutant es5 (early leaf senescence 5) in rice exhibiting leaf yellowing phenotype after the 4-leaf stage. This phenotype was confirmed by the higher accumulation of reactive oxygen species (ROS) and malondialdehyde (MDA), the disintegration of chloroplasts, reduction in chlorophyll content and photosynthetic rate and up-regulation of senescence-associated genes (SAGs) like Osh36, OsI57, and OsI85. Positional cloning revealed that the es5 phenotype is the result of one base substitution in ES5, encoding phosphatidylserine synthase (PSS) family protein, which is involved in the base-exchange type reaction to synthesize the minor membrane phospholipid phosphatidylserine. Functional complementation of ES5 in the es5 plants completely restored the wild-type phenotype. Ultra-high-performance liquid chromatography (UHPLC) analysis showed that es5 plants had increased levels of phosphatidylserine (PS) and decreased level of phosphatidylcholine (PC). These results provide evidence about the role of PS in rice leaf senescence.
Triple negative breast cancer (TNBC) originates from a less differentiated ductal cell of breast, which is less sensitive to chemotherapy. The chemotolerance mechanism of TNBC has not yet been studied in detail. For this reason, molecular profiles (expression/genetic/epigenetic) of Y654-p-β-catenin (active) and its kinase epidermal growth factor receptor (EGFR) along with SH3GL2 (regulator of EGFR homeostasis) were compared between neoadjuvant chemotherapy treated (NACT) and pretherapeutic TNBC samples. Reduced nuclear expression of Y654-p-β-catenin protein with low proliferation index and CD44 prevalence showed concordance with reduced expression of EGFR/Y1045-p-EGFR proteins in the NACT samples than the pretherapeutic TNBC samples. Infrequent messenger RNA expression, gene amplification (10–32.5%), and mutation (1%) of EGFR were seen in the TNBC samples irrespective of therapy, suggesting the importance of EGFR protein stabilization in this tumor. The upregulation of SH3GL2 seen in the NACT samples in contrast to the pretherapeutic samples might be due to its promoter hypomethylation, as seen in the quantitative methylation assay. A similar trend of upregulation of SH3GL2 and downregulation of EGFR, Y1045-p-EGFR, Y654-p-β-catenin were seen in the MDA-MB-231 cell line using antharacycline antitumor drugs (doxorubicin/nogalamycin). The NACT patients with reduced expression of Y654-p-β-catenin and/or EGFR and high expression of SH3GL2 showed comparatively better prognosis than the pretherapeutic patients. Thus, our study showed that reduced nuclear expression of Y654-p-β-catenin in NACT samples due to downregulation of EGFR protein through promoter hypomethylation-mediated upregulation of SH3GL2, resulting in low proliferation index/CD44 prevalence with better prognosis of the NACT patients, might have an important role in the chemotolerance of TNBC. 相似文献
The human telomeric DNA sequence with four repeats can fold into a parallel-stranded propeller-type topology. NMR structures solved under molecular crowding experiments correlate with the crystal structures found with crystal-packing interactions that are effectively equivalent to molecular crowding. This topology has been used for rationalization of ligand design and occurs experimentally in a number of complexes with a diversity of ligands, at least in the crystalline state. Although G-quartet stems have been well characterized, the interactions of the TTA loop with the G-quartets are much less defined. To better understand the conformational variability and structural dynamics of the propeller-type topology, we performed molecular dynamics simulations in explicit solvent up to 1.5 μs. The analysis provides a detailed atomistic account of the dynamic nature of the TTA loops highlighting their interactions with the G-quartets including formation of an A:A base pair, triad, pentad and hexad. The results present a threshold in quadruplex simulations, with regards to understanding the flexible nature of the sugar-phosphate backbone in formation of unusual architecture within the topology. Furthermore, this study stresses the importance of simulation time in sampling conformational space for this topology. 相似文献
Almost all proteins fold via a number of partially structured intermediates such as molten globule (MG) and pre-molten globule states. Understanding the structure of these intermediates at atomic level is often a challenge, as these states are observed under extreme conditions of pH, temperature, and chemical denaturants. Furthermore, several other processes such as chemical modification, site-directed mutagenesis (or point mutation), and cleavage of covalent bond of natural proteins often lead to MG like partially unfolded conformation. However, the dynamic nature of proteins in these states makes them unsuitable for most structure determination at atomic level. Intermediate states studied so far have been characterized mostly by circular dichroism, fluorescence, viscosity, dynamic light scattering measurements, dye binding, infrared techniques, molecular dynamics simulations, etc. There is a limited amount of structural data available on these intermediate states by nuclear magnetic resonance (NMR) and hence there is a need to characterize these states at the molecular level. In this review, we present characterization of equilibrium intermediates by biophysical techniques with special reference to NMR. 相似文献
Hoolock gibbons (genus Hoolock) are a group of very endangered primate species that belong to the small ape family (family Hylobatidae). The entire population that is distributed in the northeast and southeast of Bangladesh is estimated to include only around 350 individuals. A conservation program is thus necessary as soon as possible. Genetic markers are significant tools for planning such programs. In this study, we examined chromosomal characteristics of two western hoolock gibbons that were captured in a Bangladesh forest. During chromosome analysis, we encountered two chromosome variations that were observed for the first time in the wild-born western hoolock gibbons (Hoolock hoolock). The first one was a nonhomologous centromere position in chromosome 8 that was observed in the two examined individuals. The alteration was identical in the two individuals, which were examined by G-band and DAPI-band analyses. Chromosome paint analyses revealed that the difference in the centromere position was due to a single small pericentric inversion. The second variation was a heterozygous elongation in chromosome 9. Analysis by sequential techniques of fluorescence in situ hybridization with 18S rDNA and silver nitrate staining revealed a single and an inverted tandem duplication, respectively, of the nucleolus organizer region in two individuals. These chromosome variations provide useful information for the next steps to consider the evolution and conservation of the hoolock gibbon. 相似文献
Infectious bursal disease virus (IBDV) causes an economically significant disease of chickens worldwide. Very virulent IBDV (vvIBDV) strains have emerged and induce as much as 60% mortality. The molecular basis for vvIBDV pathogenicity is not understood, and the relative contributions of the two genome segments, A and B, to this phenomenon are not known. Isolate 94432 has been shown previously to be genetically related to vvIBDVs but exhibits atypical antigenicity and does not cause mortality. Here the full-length genome of 94432 was determined, and a reverse genetics system was established. The molecular clone was rescued and exhibited the same antigenicity and reduced pathogenicity as isolate 94432. Genetically modified viruses derived from 94432, whose vvIBDV consensus nucleotide sequence was restored in segment A and/or B, were produced, and their pathogenicity was assessed in specific-pathogen-free chickens. We found that a valine (position 321) that modifies the most exposed part of the capsid protein VP2 critically modified the antigenicity and partially reduced the pathogenicity of 94432. However, a threonine (position 276) located in the finger domain of the virus polymerase (VP1) contributed even more significantly to attenuation. This threonine is partially exposed in a hydrophobic groove on the VP1 surface, suggesting possible interactions between VP1 and another, as yet unidentified molecule at this amino acid position. The restored vvIBDV-like pathogenicity was associated with increased replication and lesions in the thymus and spleen. These results demonstrate that both genome segments influence vvIBDV pathogenicity and may provide new targets for the attenuation of vvIBDVs. 相似文献
Alzheimer’s disease (AD) is a progressive neurodegenerative disorder resulting in cognitive decline and enhancement of oxidative loads in the brain. Flavonoids have been considered to exert human health benefits by anti-oxidant and anti-inflammatory properties. The present study is aimed to elucidate the neuroprotective effect of catechin hydrate (CH), a natural flavanoid with potential antioxidant and anti-inflammatory properties, on intracerebroventricular streptozotocin (ICV-STZ) induced neuronal loss and memory impairment. To test this hypothesis, male Wistar rats were pretreated with CH (10 and 20 mg/kg bwt) orally once daily for 21 days and then bilaterally injected with ICV-STZ (3 mg/kg bwt), while sham group rats receive the same volume of vehicle. After 2 weeks of ICV-STZ infusion, rats were tested for cognitive performance using Morris water maze (MWM) test and then sacrifice for biochemical and histopathological assays. CH was found to be successful in upregulating the antioxidant status and prevented the memory loss. The expression of choline acetyl transferase (ChAT) was decreased in ICV-STZ group and CH pretreatment increases the expression of ChAT. Moreover, inflammatory mediators like TNF-α, IL-1β levels and expression of iNOS were significantly attenuated by CH pretreatment. The study suggests that CH is effective in preventing memory loss, ameliorating the oxidative stress and might be beneficial for the treatment of sporadic dementia of Alzheimer’s type (SDAT). 相似文献