ROS-dependent signaling pathways in plants and algae exposed to high light: Comparisons with other eukaryotes

Abstract Like all aerobic organisms, plants and algae co-opt reactive oxygen species (ROS) as signaling molecules to drive cellular responses to changes in their environment. In this respect, there is considerable commonality between all eukaryotes imposed by the constraints of ROS chemistry, similar metabolism in many subcellular compartments, the requirement for a high degree of signal specificity and the deployment of thiol peroxidases as transducers of oxidizing equivalents to regulatory proteins. Nevertheless, plants and algae carry out specialised signaling arising from oxygenic photosynthesis in chloroplasts and photoautotropism, which often induce an imbalance between absorption of light energy and the capacity to use it productively. A key means of responding to this imbalance is through communication of chloroplasts with the nucleus to adjust cellular metabolism. Two ROS, singlet oxygen (1O2) and hydrogen peroxide (H2O2), initiate distinct signaling pathways when photosynthesis is perturbed. 1O2, because of its potent reactivity means that it initiates but does not transduce signaling. In contrast, the lower reactivity of H2O2 means that it can also be a mobile messenger in a spatially-defined signaling pathway. How plants translate a H2O2 message to bring about changes in gene expression is unknown and therefore, we draw on information from other eukaryotes to propose a working hypothesis. The role of these ROS generated in other subcellular compartments of plant cells in response to HL is critically considered alongside other eukaryotes. Finally, the responses of animal cells to oxidative stress upon high irradiance exposure is considered for new comparisons between plant and animal cells

Female choice for heterozygous mates changes along successive matings in a lizard

Female mate choice and female multiple mating are major focuses of studies on sexual selection. In a multiple mating context, the benefits of mate choice can change along successive matings, and female choice would be expected to change accordingly. We investigated sequential female mate choice in the moderately polyandrous common lizard (Zootoca vivipara, synonym Lacerta vivipara). Along successive mating opportunities, we found that females were relatively unselective for the first mate, but accepted males of higher heterozygosity for subsequent mating, consistent with the trade-up choice hypothesis. We discuss the evidence of trade-up mate choice in squamates and generally trade-up for mate heterozygosity in order to motivate new studies to fill gaps on these questions

A mutation in the Arabidopsis mTERF-related plastid protein SOLDAT10 activates retrograde signaling and suppresses ¹O₂-induced cell death

The conditional flu mutant of Arabidopsis thaliana generates singlet oxygen (1O2) in plastids during a dark-to-light shift. Seedlings of flu bleach and die, whereas mature plants stop growing and develop macroscopic necrotic lesions. Several suppressor mutants, dubbed singlet oxygen-linked death activator (soldat), were identified that abrogate 1O2-mediated cell death of flu seedlings. One of the soldat mutations, soldat10, affects a gene encoding a plastid-localized protein related to the human mitochondrial transcription termination factor mTERF. As a consequence of this mutation, plastid-specific rRNA levels decrease and protein synthesis in plastids of soldat10 is attenuated. This disruption of chloroplast homeostasis in soldat10 seedlings affects communication between chloroplasts and the nucleus and leads to changes in the steady-state concentration of nuclear gene transcripts. The soldat10 seedlings suffer from mild photo-oxidative stress, as indicated by the constitutive up-regulation of stress-related genes. Even though soldat10/flu seedlings overaccumulate the photosensitizer protochlorophyllide in the dark and activate the expression of 1O2-responsive genes after a dark-to-light shift they do not show a 1O2-dependent cell death response. Disturbance of chloroplast homeostasis in emerging soldat10/flu seedlings seems to antagonize a subsequent 1O2-mediated cell death response without suppressing 1O2-dependent retrograde signaling. The results of this work reveal the unexpected complexity of what is commonly referred to as 'plastid signaling'

Condition dependence of reproductive strategy and the benefits of polyandry in a viviparous lizard

Species in which males do not contribute to reproduction beyond the provision of sperm offer good opportunities to study the potential genetic benefits that females can obtain from polyandry. Here, we report the results of a study examining the relationships between polyandry and components of female fitness in the common lizard (Lacerta vivipara). We found that polyandrous females produce larger clutches than monandrous females. Polyandrous females also lose fewer offspring during the later stages of gestation and at birth, but we did not find any relationship between polyandry and physical characteristics of viable neonates. Our results were consistent with the predictions of the intrinsic male quality hypothesis, while inbreeding avoidance and genetic incompatibility avoidance might also explain some part of the variation observed in clutch size. Moreover, the benefits of polyandry appeared to depend on female characteristics, as revealed by an interaction between reproductive strategy and female length on reproductive success. Thus, all females did not benefit equally from mating with multiple males, which could explain why polyandry and monandry coexist

Laser-induced breakdown spectroscopy analysis of bacteria. What femtosecond lasers make possible

International audienceLaser Induced Breakdown Spectroscopy spectra of bacteria, with nanosecond and femtosecond ablation, are compared. High sensitivity for mineral trace detections, larger intensity from molecular bands and precise kinetic study are among benefits using short pulses

Femtosecond time-resolved laser-induced breakdown spectroscopy for detection and identification of bacteria : a comparison to the nanosecond regime

International audienceBacterial samples (Escherichia coli and Bacillus subtilis) have been analyzed by laser-induced breakdown spectroscopy (LIBS) using femtosecond pulses. We compare the obtained spectra with those resulting from the classical nanosecond LIBS. Specific features of femtosecond LIBS have been demonstrated, very attractive for analyzing biological sample: (i) a lower plasma temperature leading to negligible nitrogen and oxygen emissions from excited ambient air and a better contrast in detection of trace mineral species; and (ii) a specific ablation regime that favors intramolecular bonds emission with respect to atomic emission. A precise kinetic study of molecular band head intensities allows distinguishing the contribution of native CN bonds released by the sample from that due to carbon recombination with atmospheric nitrogen. Furthermore a sensitive detection of trace mineral elements provide specific spectral signature of different bacteria. An example is given for the Gram test provided by different magnesium emissions from Escherichia coli and Bacillus subtilis. An entire spectrum consists of hundred resolved lines belonging to 13 atomic or molecular species, which provides an ensemble of valuable data to identify different bacteria

Spectral signature of native CN bonds for bacterium detection and identification using femtosecond laser-induced breakdown spectroscopy

International audienceA sample of Escherichia coli has been analyzed by laser-induced breakdown spectroscopy (LIBS) using femtosecond pulses. The spectrum shows strong CN molecular bands due to the direct ablation of native CN molecular bonds from the bacteria in contrast with weak atomic lines from carbon. The native nature of the observed CN bonds is supported by the kinetic behavior of the CN band head which rapidly decays with a time constant of 94 ns, while for a pure graphite sample the CN band head increases with a delay of 450 ns due to recombination with the ambient air. Moreover, about hundred resolved lines belonging to 12 atomic or molecular species are recorded, providing a valuable spectral signature to identify the bacterium