Thermal modelling of gas generation and retention in the Jurassic organic-rich intervals in the Darquain field, Abadan Plain, SW Iran

The petroleum system with Jurassic source rocks is an important part of the hydrocarbons discovered in the Middle East. Limited studies have been done on the Jurassic intervals in the 26,500 km2 Abadan Plain in south-west Iran, mainly due to the deep burial and a limited number of wells that reach the basal Jurassic successions. The goal of this study was to evaluate the Jurassic organic-rich intervals and shale gas play in the Darquain field using organic geochemistry, organic petrography, biomarker analysis, and basin modelling methods. This study showed that organic-rich zones present in the Jurassic intervals of Darquain field could be sources of conventional and unconventional gas reserves. The organic matter content of samples from the organic-rich zones corresponds to medium-to-high-sulphur kerogen Type II-S marine origin. The biomarker characteristics of organic-rich zones indicate carbonate source rocks that contain marine organic matter. The biomarker results also suggest a marine environment with reducing conditions for the source rocks. The constructed thermal model for four pseudo-wells indicates that, in the kitchen area of the Jurassic gas reserve, methane has been generated in the Sargelu and Neyriz source rocks from Early Cretaceous to recent times and the transformation ratio of organic matter is more than 97%. These organic-rich zones with high initial total organic carbon (TOC) are in the gas maturity stage [1.5–2.2% vitrinite reflectance in oil (Ro)] and could be good unconventional gas reserves and gas source rocks. The model also indicates that there is a huge quantity of retained gas within the Jurassic organic-rich intervals

Molecular Study and Photosynthetic- Senescence Related Gene in Flag Leaf and Other Leaves in Barley

In order to find out the importance of flag leaf in Hordeum vulgare L. cv. Hordea in some physiologic traits and photosynthetic and leaf senescence-related gene expression, a field experiment was carried out in Warwick University Research Farm, UK, in 2003. For more accuracy and statistical comparison of the calculated means, the experiment was carried out in 4 replicates. Random leaf samples were taken in 3 periodic times during the plant growth. The studied traits included chlorophyll a, b content, net CO2 assimilation, Fv/Fm ratio, cellular oxidative level (TBARM) and photosynthetic and senescence-related gene expression. Chlorophyll content showed a decreasing trend during the sampling periods. This was greater in other leaves than flag leaf. Net CO2 assimilation rate in flag leaf was greater and more stable than other leaves during the sampling periods. TBARM content went up very fast by progression of leaf senescence. Photosynthetic genes RCBS, LhcII and Cab showed similar expression pattern and generally decreased by by progression of leaf senescence, especially in other leaves. In genes related to leaf senescence, there was notable variety. Expression of MTI and CATI showed relatively similar pattern, whereas SODI and SAG12 showed different expression. In conclusion, results showed that flag leaf had superior role in increasing grain yield. This was due to stability of photosynthesis, chlorophyll content as well as less oxidative damage during flag-leaf senescence, as compared to other leaves. In this respect, activity of photosynthesis genes and homeostatic senescence-related genes significantly was expressed during flag-leaf senescence

Photosynthetic Metabolism and Antioxidant System of Spike and Flag Leaf of Bread Wheat under Drought Stress

IntroductionDrought stress and consequent lack of available water for plants is one of the main causes of accumulation of reactive oxygen species (ROS) in various organs of plants, which is effective in reducing the yield of cereals such as wheat. The antioxidant system, which contains various enzymes and genes, is responsible for removing and detoxifying plants from ROS. Unfortunately, genes responding to drought stress and their enzymatic activities associated with spike and flag leaf of wheat have received less attention. Therefore, in the present study, photosynthetic parameters, key enzymes of the antioxidant system, and expression analysis of some genes involved in this system under field capacity (FC) and drought stress (DS) conditions in spike and flag leaves of wheat were investigated.Materials and MethodsThe present study was performed in Azadshahr Research Center, Golestan Province, Iran in 2021. The wheat cultivar used in this study was Qaboos. This cultivar was cultivated under two experimental conditions of field capacity and drought stress in a randomized complete block design with three replications in the field. In the present study, differences in net photosynthesis (PN) rate, transpiration (E), stomatal conductance (gs), chlorophyll (Chl), relative water content (RWC), and the activity of APX, DHAR, MDHAR, and GR enzymes involved in the antioxidant system of flag leaf and spike of wheat were examined under field capacity and drought stress conditions. Transcription levels of APX, DHAR, MDHAR, and GR genes were measured using qRT-PCR under drought stress and field capacity conditions. Flag leaf and spike of Wheat for photosynthetic parameters and enzymatic activities at 0, 5, 10, 15, 20, and 25 and relative gene expression at 0, 1, 3, 5, 10, 15, 20, and 25 days after anthesis (DAA) were harvested. The recorded data were analyzed by analysis of variance and all analyzes were performed by SPSS software. Mean differences were compared using Duncan's multiple range test at 5% probability level.Results and DiscussionIn general, the spike had a better capacity to maintain net photosynthesis, transpiration, stomatal conductance, chlorophyll, and relative water content under drought stress conditions. This superiority reached its peak on the fifth day after anthesis. The enzymatic activity of the antioxidant system was normal under field capacity conditions. However, with the application of drought stress, APX, DHAR, MDHAR, and GR enzymes were affected in both spike and flag leaf of wheat and their activity increased, which indicates more activity of the antioxidant system in spikes and flag leaf of wheat for controls the level of ROS. After more days of grain filling, the activity of enzymes increased, and finally, after the plant entered the senescence stage, the activity of enzymes decreased to some extent. With drought stress, the antioxidant system in spike, especially from the 10th day after anthesis onwards, had a better performance. However, enzymatic activity in flag leaves under drought stress was not significantly different from field capacity conditions. Transcriptional levels of APX, DHAR, MDHAR, and GR genes associated with the antioxidant system increased under drought stress compared to field capacity conditions. It seems that the increase in enzymatic activity simultaneously with the increase in the level of transcription of the genes of the antioxidant system in the spikes and flag leaves of wheat is to counteract the oxidative damage.ConclusionIn the present study, spikes of wheat played a more important role in responding to water deficiency through the antioxidant system than its flag leaf. The results of this study showed a high potential of the spike compared to flag leaf in the face of drought stress and this results in future breeding programs in wheat can play a key role in selecting drought-resistant cultivars with high yield

Enterohaemorrhagic Escherichia coli O157:H7 target Peyer's patches in humans and cause attaching/effacing lesions in both human and bovine intestine

BACKGROUND—Enterohaemorrhagic Escherichia coli (EHEC) constitute a significant risk to human health worldwide, and infections, particularly with serogroup O157:H7, are associated with consumption of a variety of food and water vehicles, particularly food of bovine origin. EHEC cause acute gastroenteritis, bloody diarrhoea, and haemorrhagic colitis; up to 10% of cases develop severe complications, including the haemolytic uraemic syndrome, with a 5% case fatality. A virulence characteristic of enteropathogenic E coli, the attaching/effacing lesion, is considered to be important in EHEC. However, although EHEC produce this lesion on cultured human cells, this has not been demonstrated on human intestinal mucosal surfaces. In addition, the initial site(s) of colonisation of EHEC in humans is not known.
AIMS—To assess the association of EHEC O157:H7 with paediatric and bovine intestine using in vitro organ culture and determine if attaching/effacing lesions occur.
METHODS—Ultrastructural analysis of in vitro intestinal organ cultures of human small and large intestine was used to investigate adhesion of O157:H7 EHEC to intestinal surfaces. Bovine intestinal organ culture was used to examine the pathology produced by the same EHEC strain in cattle.
RESULTS—The study showed that EHEC O157:H7 adhered to human intestinal mucosa. Binding and attaching/effacing lesion formation of O157:H7 in humans was restricted to follicle associated epithelium of Peyer's patches. The same strain caused attaching/effacing lesions on bovine mucosa.
CONCLUSIONS—O157:H7 targets follicle associated epithelium in humans where it causes attaching/effacing lesions. The same human isolate can cause attaching/effacing lesions in cattle, indicating that similar pathogenic mechanisms operate across human and bovine species


Keywords: Escherichia coli; enterohaemorrhagic E coli O157:H7; Peyer's patches; attaching/effacing lesio

Isolation and molecular characterization of the RecQsim gene in Arabidopsis, rice (Oryza sativa) and rape (Brassica napus)

In any organism that reproduces sexually, DNA Recombination plays vital roles in the generation of allelic diversity as well as in preservation of genome fidelity. Genome fidelity is particularly important in plants because mutations occurring during the development of flowering plants are heritable and can be passed onto the next generation. One of the gene families that play crucial roles in the regulation of DNA recombination and repair is the RecQ family of DNA helicases. In flowering plants, RecQ family members have only been characterized in Arabidopsis. Among all RecQ family members, the Arabidopsis RecQsim is distinct in that there is a substantial insertion (of around 100 amino acids) inside its helicase domain. We previously showed that this novel RecQ homologue is expressed in various organs of Arabidopsis and rice. We also showed that the Arabidopsis RecQsim gene when ectopically expressed in yeast RecQ deficient (sgs1) cells, can partially compensate for the absence of SGS1. Here, we perform an evolutionary analysis of RecQsim orthologues isolated from rice and rape together with other known plant RecQ family members. Furthermore, isolation and molecular characterization of two Arabidopsis recQsim knockout mutants is explained. The position of T-DNA integration suggests that the recQsim-1 is likely to be a real knockout while recQsim-2 is expected to be a knockdown mutant. Segregation analysis of the T-DNA selectable marker together with Southern hybridization revealed that in both isolated mutant lines a single copy of the T-DNA is inserted into the genome. Analysis of these mutant lines will provide evidence on the roles that RecQsim plays in DNA recombination and the regulation of leaf senescence in plants and may open new insights into how plants respond to various environmental challenges