Water Relation Alterations Observed during Hypersensitive Reaction Induced by Bacteria

Upon exposure to pathogenic bacteria, resistant and nonhost plants undergo a hypersensitive reaction (HR) that is expressed as rapid plant cell death. If sufficient concentrations of these bacteria are inoculated to such plant tissue, then that portion of the tissue rapidly collapses and becomes necrotic. As the tissue collapses the water relations of inoculated tissues become markedly disturbed. We measured a decline in the relative water content (RWC) in the leaf-like cotyledons of cotton (Gossypium hirsutum cv Immune 216) within the first 4 h (cut at 1 h) after inoculation with Pseudomonas syringae pv tabaci. However, the decrease in RWC was not caused by a decrease in initial fresh weight but by increased water uptake during incubation in water. By 8 h after inoculation, cotyledons still on the plant had lost turgidity, and their area decreased. K+ efflux was also observed concurrently with the decrease in RWC, providing a reason for the loss of turgidity in the tissue. These observations suggest that cells lose turgor and change shape from cylinders with large intercellular spaces to those of a more tabular shape. During this change cell walls come closer together, providing an avenue for increased water uptake through capillary action. The stomatal diffusive resistance of intact cotyledons increased; hence, water loss through stomata is not the cause of the observed wilting and RWC decline. An increase in K+ per dry weight suggests that phloem loading or movement may also be impaired during bacterially induced HR.     

Genetic Admixture in the Culturally Unique Peranakan Chinese Population in Southeast Asia

The Peranakan Chinese are culturally unique descendants of immigrants from China who settled in the Malay Archipelago ∼300–500 years ago. Today, among large communities in Southeast Asia, the Peranakans have preserved Chinese traditions with strong influence from the local indigenous Malays. Yet, whether or to what extent genetic admixture co-occurred with the cultural mixture has been a topic of ongoing debate. We performed whole-genome sequencing (WGS) on 177 Singapore (SG) Peranakans and analyzed the data jointly with WGS data of Asian and European populations. We estimated that Peranakan Chinese inherited ∼5.62% (95% confidence interval [CI]: 4.76–6.49%) Malay ancestry, much higher than that in SG Chinese (1.08%, 0.65–1.51%), southern Chinese (0.86%, 0.50–1.23%), and northern Chinese (0.25%, 0.18–0.32%). A sex-biased admixture history, in which the Malay ancestry was contributed primarily by females, was supported by X chromosomal variants, and mitochondrial (MT) and Y haplogroups. Finally, we identified an ancient admixture event shared by Peranakan Chinese and SG Chinese ∼1,612 (95% CI: 1,345–1,923) years ago, coinciding with the settlement history of Han Chinese in southern China, apart from the recent admixture event with Malays unique to Peranakan Chinese ∼190 (159–213) years ago. These findings greatly advance our understanding of the dispersal history of Chinese and their interaction with indigenous populations in Southeast Asia.     

Biodeterioration of Mayan buildings at uxmal and tulum,Mexico

Uxmal and Tulum are two important Mayan sites in the Yucatan peninsula. The buildings are mainly composed of limestone and grey/black discoloration is seen on exposed walls and copious greenish biofilms on inner walls. The principal microorganisms detected on interior walls at both Uxmal and Tulum were cyanobacteria; heterotrophic bacteria and filamentous fungi were also present. A dark‐pigmented mitosporic fungus and Bacillus cereus, both isolated from Uxmal, were shown to be acidogenic in laboratory cultures. Cyanobacteria belonging to rock‐degrading genera Synechocystis and Gloeocapsa were identified at both sites. Surface analysis previously showed that calcium ions were present in the biofilms on buildings at Uxmal and Tulum, suggesting the deposition of biosolubilized stone. Apart from their potential to degrade the substrate, the coccoid cyanobacteria supply organic nutrients for bacteria and fungi, which can produce organic acids, further increasing stone degradation.     

Methylated DNA/RNA in Body Fluids as Biomarkers for Lung Cancer

DNA/RNA methylation plays an important role in lung cancer initiation and progression. Liquid biopsy makes use of cells, nucleotides and proteins released from tumor cells into body fluids to help with cancer diagnosis and prognosis. Methylation of circulating tumor DNA (ctDNA) has gained increasing attention as biomarkers for lung cancer. Here we briefly introduce the biological basis and detection method of ctDNA methylation, and review various applications of methylated DNA in body fluids in lung cancer screening, diagnosis, prognosis, monitoring and treatment prediction. We also discuss the emerging role of RNA methylation as biomarkers for cancer.     

Water Transfer in an Alfalfa/Maize Association : Survival of Maize during Drought

We investigated the possibility of interspecific water transfer in an alfalfa (Medicago sativa L.) and maize (Zea mays L.) association. An alfalfa plant was grown through two vertically stacked plastic tubes. A 5 centimeter air gap between tubes was bridged by alfalfa roots. Five-week old maize plants with roots confined to the top tube were not watered, while associated alfalfa roots had free access to water in the bottom tube (the −/+ treatment). Additional treatments included: top and bottom tubes watered (+/+), top and bottom tubes droughted (−/−), and top tube droughted after removal of alfalfa root bridges and routine removal of alfalfa tillers (−^*). Predawn leaf water potential of maize in the −/+ treatment fell to −1.5 megapascals 13 days after the start of drought; thereafter, predawn and midday potentials were maintained near −1.9 megapascals. Leaf water potentials of maize in the −/− and −^* treatments declined steadily; all plants in these treatments were completely desiccated before day 50. High levels of tritium activity were detected in water extracted from both alfalfa and maize leaves after ³H₂O was injected into the bottom −/+ tube at day 70 or later. Maize in the −/+ treatment was able to survive an otherwise lethal period of drought by utilizing water lost by alfalfa roots.     

Synergism between interleukin-6 and interleukin-1beta in hypothalamic serotonin release: a reverse in vivo microdialysis study in F344 rats

The effects of interleukin-1beta (IL-1beta) and interleukin-6 (IL-6) perfused locally into the anterior hypothalamus (AHY) on serotonin (5-hydroxytryptamine, 5-HT) release were investigated in the same region using in vivo microdialysis in conscious, freely moving F344 rats. IL-1beta (1 ng/rat) or IL-6 (50 ng/rat) injected directly into the AHY elicited a rapid and transient statistically significant increase in extracellular 5-HT levels (to 161% and 145% of the respective AUC (area under the curve) basal value, 100%). Intra-hypothalamic infusion of IL-1-receptor antagonist IL-1Ra (2 mug/rat) prevented this effect of IL-1beta, but not that of IL-6, suggesting an IL-1beta-independent mechanism for hypothalamic 5-HT release by this latter cytokine. Furthermore, intra-hypothalamic co-perfusion of IL-6 with IL-1beta at sub-optimal doses (10 ng/rat and 0.5 ng/rat, respectively) synergized in releasing hypothalamic 5-HT, thus providing in vivo evidence that both cytokines, IL-6 and IL-1beta are able to modulate the neuronal 5-HT response in the rat AHY.     

Apoptosis: Identification of dying cells

Cell death is usually classified into two broad categories: apoptosis and necrosis. Necrosis is a passive, catabolic process, always pathological, that represents a cell's response to extreme accidental or toxic insults. Apoptosis, in contrast, occurs under normal physiological conditions and is an active process requiring energy. However, apoptosis can also be elicited in a pathological way by toxic injury or during disease processes. In these nonphysiological conditions, both types of cell death can be encountered following the same initial insult and the balance between death by apoptosis and by necrosis appears to depend upon the intensity of the injury and the level of available intracellular ATP. It is important, however, to discriminate between apoptosis and necrosis in pathological conditions, as therapeutic intervention could be considered in apoptotic cell death with putative new pharmacological agents aimed at interfering with the key molecular events involved. In most cases, none of the current laboratory techniques used alone allows for unambiguous identification of apoptotic cells. Some of the most common methods based on morphology, biochemistry, and plasma membrane changes are discussed in terms of specificity and possible sources of error in data interpretation. As a rule, classification of cell death in a given model should always include morphological examination coupled with at least one of the other assays.     

Chloroplast Structure and Function Is Altered in the NCS2 Maize Mitochondrial Mutant

The nonchromosomal stripe 2 (NCS2) mutant of maize (Zea mays L.) has a DNA rearrangement in the mitochondrial genome that segregates with the abnormal growth phenotype. Yet, the NCS2 characteristic phenotype includes striped sectors of pale-green tissue on the leaves. This suggests a chloroplast abnormality. To characterize the chloroplasts present in the mutant sectors, we examined the chloroplast structure by electron microscopy, chloroplast function by radiolabeled carbon dioxide fixation and fluorescence induction kinetics, and thylakoid protein composition by polyacrylamide gel electrophoresis. The data from these analyses suggest abnormal or prematurely arrested chloroplast development. Deleterious effects of the NCS2 mutant mitochondria upon the cells of the leaf include structural and functional alterations in the both the bundle sheath and mesophyll chloroplasts.