Light acclimation,retrograde signalling,cell death and immune defences in plants

This review confronts the classical view of plant immune defence and light acclimation with recently published data. Earlier findings have linked plant immune defences to nucleotide‐binding site leucine‐rich repeat (NBS‐LRR)‐dependent recognition of pathogen effectors and to the role of plasma membrane‐localized NADPH‐dependent oxidoreductase (AtRbohD), reactive oxygen species (ROS) and salicylic acid (SA). However, recent results suggest that plant immune defence also depends on the absorption of excessive light energy and photorespiration. Rapid changes in light intensity and quality often cause the absorption of energy, which is in excess of that required for photosynthesis. Such excessive light energy is considered to be a factor triggering photoinhibition and disturbance in ROS/hormonal homeostasis, which leads to cell death in foliar tissues. We highlight here the tight crosstalk between ROS‐ and SA‐dependent pathways leading to light acclimation, and defence responses leading to pathogen resistance. We also show that LESION SIMULATING DISEASE 1 (LSD1) regulates and integrates these processes. Moreover, we discuss the role of plastid–nucleus signal transduction, photorespiration, photoelectrochemical signalling and ‘light memory’ in the regulation of acclimation and immune defence responses. All of these results suggest that plants have evolved a genetic system that simultaneously regulates systemic acquired resistance (SAR), cell death and systemic acquired acclimation (SAA).     

Interpretation of Changes in Circulating Tumor Cell Counts

The presence of circulating tumor cells (CTCs) in the blood of cancer patients may guide the use of therapy. We investigated how to evaluate a reduction in the number of CTCs after administration of therapy. CTCs were enumerated with the CellSearch system in 111 metastatic breast and 185 metastatic prostate cancer patients before start of a new line of chemotherapy and after initiation of therapy. Different means to express changes in CTC counts were evaluated with respect to overall survival (OS). A static CTC cutoff is the best method to determine whether a therapy is effective. This is exemplified by the highest Cox hazard ratio of 2.1 for OS; three methods to express relative differences performed worse. A lookup table is provided from which the significance of a change in CTCs can be derived. The aim of therapy should be the elimination of all CTCs. A period of 10 to 12 weeks of therapy is needed to reach the treatment effect on CTCs.     

Multivalent binding of PWWP2A to H2A.Z regulates mitosis and neural crest differentiation

Replacement of canonical histones with specialized histone variants promotes altering of chromatin structure and function. The essential histone variant H2A.Z affects various DNA‐based processes via poorly understood mechanisms. Here, we determine the comprehensive interactome of H2A.Z and identify PWWP2A as a novel H2A.Z‐nucleosome binder. PWWP2A is a functionally uncharacterized, vertebrate‐specific protein that binds very tightly to chromatin through a concerted multivalent binding mode. Two internal protein regions mediate H2A.Z‐specificity and nucleosome interaction, whereas the PWWP domain exhibits direct DNA binding. Genome‐wide mapping reveals that PWWP2A binds selectively to H2A.Z‐containing nucleosomes with strong preference for promoters of highly transcribed genes. In human cells, its depletion affects gene expression and impairs proliferation via a mitotic delay. While PWWP2A does not influence H2A.Z occupancy, the C‐terminal tail of H2A.Z is one important mediator to recruit PWWP2A to chromatin. Knockdown of PWWP2A in Xenopus results in severe cranial facial defects, arising from neural crest cell differentiation and migration problems. Thus, PWWP2A is a novel H2A.Z‐specific multivalent chromatin binder providing a surprising link between H2A.Z, chromosome segregation, and organ development.     

High levels of genetic diversity in populations of Iris aphylla L. (Iridaceae), an endangered species in Poland

We used RAPDs (Random Amplified Polymorphic DNAs) to investigate genetic diversity and its partition within and between three populations of Iris aphylla in Poland. Analysis of Molecular Variance (AMOVA) of 84 distinct RAPD multiband genotypes revealed higher variation within populations (77.2%) than genetic differentiation between them (22.8%, P  < 0.002). Values of genetic diversity indices ( H ) were similar in all three sites (0.21–0.24). The differentiation of the populations corresponded to low average gene flow ( Nm  = 0.81). Our results indicated that genetic diversity was independent of population size. We concluded that although sexual reproduction and gene flow between populations of I. aphylla were very limited, they preserved high levels of genetic diversity. Relatively large number of seeds, which migrated in the past to populations, as well as patterns of reproduction and life history of I. aphylla may explain this situation.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 142 , 65–72.     

Chilled Galleria mellonella larvae: mechanism of supernumerary moulting

ABSTRACT. Supernumerary larval instars were produced when Galleria mellonella L. (Lepidoptera) larvae were chilled at 0°C. Although sensitivity to cooling stress of the last instar and younger larvae were generally the same, only penultimate and the last instar larvae showed a significant correlation between their age and the number of additional larval moults. Chilling stress induced a rapid and persistent increase in the JH titre of the last instar larvae. Severing the ventral nerve cord resulted in a predictable loss of the ability to produce supernumerary moults in chilled last instar larvae. The data suggest that sensory input stimulates allatotropic hormone secretion by the brain of chilled larvae. The possible mechanism controlling supernumerary moulting is discussed.     

Serotonin modulates a photic response in circadian locomotor rhythmicity of adults of the blow fly, Calliphora vicina

Abstract. The present experiments were undertaken to explore a role for serotonin (5-hydroxytryptamine, 5-HT) in modulating photic signal transduction in photoreceptors of the blow fly, Calliphora vicina. Injection of p-chlorophenylalanine (pCPA) into the haemolymph appeared to reduce sensitivity to the photic effects of constant ‘bright’ light (LL hyperactivity and circadian arrhythmicity). After drug injection in bright LL, flies continued with a free-running rhythm as in constant darkness (DD) or with a lengthened period τ as in ‘dim’ LL. When 5-HT was injected into flies kept in dim LL, they became hyperactive and arrhythmic as in bright LL. This finding suggests a potential role for serotonin as mediator of circadian changes in the insect visual system including extraretinal photoreceptors.     

A new genus and species of scorpionfly (Mecoptera) from Baltic amber,with an unusually developed postnotal organ

A new genus and species of fossil scorpionflies (Mecoptera) Baltipanorpa damzeni gen. et sp.n. is described from two well‐preserved male specimens in Baltic amber (middle Eocene: Lutetian). The most characteristic feature of the new taxon is an unusually developed postnotal organ on abdominal tergum IV. This is the most extremely developed example of this organ among Mecoptera and the only observation of notal and postnotal organs among fossil scorpionflies. The following combination of characters are provided to distinguish the new genus from other Panorpidae: Sc, short; R₁ and R₂ two‐branched; A₁ joins posterior margin of wing only at same level as fork of vein Rs; unusual shape of abdomen, abdominal segments I–IV strongly reduced, abdominal segment V elongate and widened, segments VII and VIII strongly elongate; notal and postnotal organs present, strongly developed process (postnotal organ) on tergum IV, unknown in all described extant and fossil scorpionflies. Different types of notal organs of Mecoptera are compared and their function and morphology are discussed. Morphological analysis of notal and postnotal organs in extant species permits us to conclude that B. damzeni sp.n. is characterized by the most developed and complex notal organs in all Mecoptera.     

PHYTOALEXIN DEFICIENT 4 affects reactive oxygen species metabolism,cell wall and wood properties in hybrid aspen (Populus tremula L. × tremuloides)

The PHYTOALEXIN DEFICIENT 4 (PAD4) gene in Arabidopsis thaliana (AtPAD4) is involved in the regulation of plant – pathogen interactions. The role of PAD4 in woody plants is not known; therefore, we characterized its function in hybrid aspen and its role in reactive oxygen species (ROS)‐dependent signalling and wood development. Three independent transgenic lines with different suppression levels of poplar PAD expression were generated. All these lines displayed deregulated ROS metabolism, which was manifested by an increased H₂O₂ level in the leaves and shoots, and higher activities of manganese superoxide dismutase (MnSOD) and catalase (CAT) in the leaves in comparison to the wild‐type plants. However, no changes in non‐photochemical quenching (NPQ) between the transgenic lines and wild type were observed in the leaves. Moreover, changes in the ROS metabolism in the pad4 transgenic lines positively correlated with wood formation. A higher rate of cell division, decreased tracheid average size and numbers, and increased cell wall thickness were observed. The results presented here suggest that the Populus tremula × tremuloides PAD gene might be involved in the regulation of cellular ROS homeostasis and in the cell division – cell death balance that is associated with wood development.     

Tuberculosis is associated with expansion of a motile,permissive and immunomodulatory CD16+ monocyte population via the IL-10/STAT3 axis

The human CD14⁺ monocyte compartment is composed by two subsets based on CD16 expression. We previously reported that this compartment is perturbed in tuberculosis (TB) patients, as reflected by the expansion of CD16⁺ monocytes along with disease severity. Whether this unbalance is beneficial or detrimental to host defense remains to be elucidated. Here in the context of active TB, we demonstrate that human monocytes are predisposed to differentiate towards an anti-inflammatory (M2-like) macrophage activation program characterized by the CD16⁺CD163⁺MerTK⁺pSTAT3⁺ phenotype and functional properties such as enhanced protease-dependent motility, pathogen permissivity and immunomodulation. This process is dependent on STAT3 activation, and loss-of-function experiments point towards a detrimental role in host defense against TB. Importantly, we provide a critical correlation between the abundance of the CD16⁺CD163⁺MerTK⁺pSTAT3⁺ cells and the progression of the disease either at the local level in a non-human primate tuberculous granuloma context, or at the systemic level through the detection of the soluble form of CD163 in human sera. Collectively, this study argues for the pathogenic role of the CD16⁺CD163⁺MerTK⁺pSTAT3⁺ monocyte-to-macrophage differentiation program and its potential as a target for TB therapy, and promotes the detection of circulating CD163 as a potential biomarker for disease progression and monitoring of treatment efficacy.     

Bite traces on dicynodont bones and the early evolution of large terrestrial predators

Nied?wiedzki, G., Gorzelak, P. & Sulej, T. 2010: Bite traces on dicynodont bones and the early evolution of large terrestrial predators. Lethaia, Vol. 44, pp. 87–92. Dicynodont (Synapsida: Anomodontia) bones from the Late Triassic (late Norian/early Rhaetian) of Poland yield characteristic tooth marks that can be attributed to three ichnotaxa (Linichnus serratus, Knethichnus parallelum and Nihilichnus nihilicus). The general shape and dimension of these traces perfectly match the dental morphology of a co‐occurring carnivorous dinosaur. It is therefore concluded that early carnivorous dinosaurs were feeding on dicynodonts. This discovery constitutes one of the oldest evidence of dinosaur predator–prey interaction. It is suggested that an evolutionary increase in the size of dicynodonts across the Late Triassic may have been driven by selection pressure to reach a size refuge from early dinosaur predators. □Bite traces, dicynodonts, dinosaurs, predation, Triassic.