Differing biophysical properties underpin the unique signaling potentials within the plant phytochrome photoreceptor families

Many aspects of photoperception by plants and microorganisms are initiated by the phytochrome (Phy) family of photoreceptors that detect light through interconversion between red light- (Pr) and far-red light-absorbing (Pfr) states. Plants synthesize a small family of Phy isoforms (PhyA to PhyE) that collectively regulate photomorphogenesis and temperature perception through redundant and unique actions. While the selective roles of these isoforms have been partially attributed to their differing abundances, expression patterns, affinities for downstream partners, and turnover rates, we show here from analysis of recombinant Arabidopsis chromoproteins that the Phy isoforms also display distinct biophysical properties. Included are a hypsochromic shift in the Pr absorption for PhyC and varying rates of Pfr to Pr thermal reversion, part of which can be attributed to the core photosensory module in each. Most strikingly, PhyB combines strong temperature dependence of thermal reversion with an order-of-magnitude faster rate to likely serve as the main physiological thermosensor, whereby thermal reversion competes with photoconversion. In addition, comparisons of Pfr occupancies for PhyA and PhyB under a range of red- and white-light fluence rates imply that low-light environments are effectively sensed by PhyA, while high-light environments, such as full sun, are effectively sensed by PhyB. Parallel analyses of the Phy isoforms from potato and maize showed that the unique features within the Arabidopsis family are conserved, thus indicating that the distinct biophysical properties among plant Phy isoforms emerged early in Phy evolution, likely to enable full interrogation of their light and temperature environments.

TaSCA, an Agile Survey on Chemosensory Impairments for Self-Monitoring of COVID-19 Patients: A Pilot Study

Background/Objective: During the COVID-19 pandemic, smell and taste disorders emerged as key non-respiratory symptoms. Due to widespread presence of the disease and to difficult objective testing of positive persons, the use of short surveys became mandatory. Most of the existing resources are focused on smell, very few on taste or trigeminal chemosensation called chemesthesis. However, it is possible that the three submodalities are affected differently by COVID-19.Methods: We prepared a short survey (TaSCA) that can be administered at the telephone or through online resources to explore chemosensation. It is composed of 11 items on olfaction, taste, and chemesthesis, in order to discriminate the three modalities. We avoided abstract terms, and the use of semiquantitative scales because older patients may be less engaged. Statistical handling included descriptive statistics, Pearson's chi-squared test and cluster analysis.Results: The survey was completed by 83 persons (60 females and 23 males), which reported diagnosis of COVID-19 by clinical (n = 7) or molecular (n = 18) means, the others being non-COVID subjects. Cluster analysis depicted the existence of two groups, one containing mostly asymptomatic and one mostly symptomatic subjects. All swab-positive persons fell within this second group. Only one item, related to trigeminal temperature perception, did not discriminate between the two groups.Conclusions: These preliminary results indicate that TaSCA may be used to easily track chemosensory symptoms related to COVID-19 in an agile way, giving a picture of three different chemosensory modalities.

Adjustable dual temperature-sensitive hydrogel based on self-assembly cross-linking strategy with high stretchable and healable properties

Developing smart temperature-sensitive hydrogels with wide response range, high stretchable and self-healable properties for simulation of the temperature perception function of the human skin remains a great challenge. Here, a...

Thermal balance of spinal cord injured divers during cold water diving: A case control study

Introduction: This study compared the thermal balance of spinal cord injured (SCI) divers and able-bodied (AB) divers during recreational cold-water dives. Methods: Ten divers (5 AB, 5 SCI) in matched pairs dived in a shallow lake (temperature 6°C) for 30 to 36 min wearing 5 mm ‘Long John’ neoprene wetsuits. A gastrointestinal temperature radio pill recorded gastro-intestinal temperature (Tgi) prior to, immediately after and at 5, 10, 15, 30, 60, 120 min post-dive. Subjective ratings of temperature perception were recorded concomitantly using a visual analogue scale (VAS). Results: No difference between SCI and AB divers in Tgi before the dive was observed (P = 0.85). After the dive, SCI divers cooled significantly more than AB at all measured time intervals (P < 0.001). Post dive, the mean maximum fall in Tgi during the recovery phase in SCI divers was 0.85°C (SD 0.20) and in the AB group was 0.48°C (0.48). In addition, there was greater individual variation in SCI divers compared to AB divers. There were no statistically significant differences in temperature perception between the groups either before or at any time after the dives. Conclusions: In contrast to AB divers, divers with SCI were unable to maintain Tgi during short shallow dives in 6°C water and their temperatures fell further post-dive. The reduction in Tgi was not reflected in the subjective ratings of temperature perception by the SCI divers. The study was too small to assess how the level of spinal injury influenced thermal balance.

Phytochromes B1/B2 Are Major Regulators of Ripening-associated Epigenome Reprogramming in Tomato Fruits

Phytochrome-mediated light and temperature perception has been shown to be a major regulator of fruit development. Furthermore, chromatin remodelling via DNA demethylation has been described as a crucial mechanism behind the fruit ripening process; however, the molecular basis underlying the triggering of this epigenetic modification remains largely unknown. Here, through integrative analyses of the methylome, siRNAome and transcriptome of tomato fruits from phyA and phyB1B2 null mutants, we report that PHYB1 and PHYB2 control genome-wide DNA methylation during fruit development. The experimental evidence indicates that PHYB1B2 signal transduction is mediated by the coordinated expression of DNA methylases/demethylases, histone-modifying enzymes and chromatin remodelling factors, resulting in the transcriptional regulation of photosynthetic and ripening-associated genes. This new level of understanding provides insights into the orchestration of epigenetic mechanisms in response to environmental cues affecting agronomical traits.

PHYTOCHROMES B1/B2 ARE KEY REGULATORS OF EPIGENOME REPROGRAMMING DURING TOMATO FRUIT DEVELOPMENT

Phytochrome-mediated light and temperature perception has been shown to be a major regulator of fruit development. Furthermore, chromatin remodelling via DNA demethylation has been described as a crucial mechanism behind the fruit ripening process; however, the molecular basis underlying the triggering of this epigenetic modification remains largely unknown. Here, an integrative analyses of the methylome, siRNAome and transcriptome of tomato fruits from phyA and phyB1B2 null mutants was performed, revealing that PHYB1 and PHYB2 influences genome-wide DNA methylation during fruit development and ripening. The experimental evidence indicates that PHYB1B2 signal transduction relies on a gene expression network that includes chromatin organization factors (DNA methylases/demethylases, histone-modifying enzymes and remodelling factors) and transcriptional regulators, ultimately leading to altered mRNA profile of photosynthetic and ripening-associated genes. This new level of understanding provides insights into the orchestration of epigenetic mechanisms in response to environmental cues affecting agronomical traits in fleshy fruits.