Evaluation of the roles of brassinosteroid, gibberellin and auxin for tomato internode elongation in response to low red:far-red light.

In this study, we explore the interplay between the plant hormones gibberellins (GA), brassinosteroids (BR), and Indole-3-Acetic Acid (IAA) in their collective impact on plant shade avoidance elongation under varying light conditions. We focus particularly on low Red:Far-red (R:FR) light conditions achieved by supplementing the background light with FR. We characterized the tomato internode response to low R:FR and, with RNA-seq analysis, we were able to identify some of the potential regulatory hormonal pathways. Through a series of exogenous pharmacological modulations of GA, IAA, and BR, we demonstrate that GA and BR are sufficient but also necessary for inducing stem elongation under low R:FR light conditions. Intriguingly, while IAA alone shows limited effects, its combination with GA yields significant elongation, suggesting a nuanced hormonal balance. Furthermore, we unveil the complex interplay of these hormones under light with low R:FR, where the suppression of one hormone's effect can be compensated by the others. This study provides insights into the hormonal mechanisms governing plant adaptation to light, highlighting the intricate and adaptable nature of plant growth responses. Our findings have far-reaching implications for agricultural practices, offering potential strategies for optimizing plant growth and productivity in various lighting environments.

Knowledge and attitudes of healthcare personnel about vaccination of migrant and refugee children and adolescents.

Background: The number of migrants to Greece has increased considerably the last decade. This study assessed the knowledge and attitudes of healthcare personnel (HCP) toward vaccination of newly-arrived children and adolescents in the Aegean islands, a major port of entry of migrants and refugees to Europe. Methods: The study was conducted from September 2020 to January 2021. All (166) HCP employed in the public health sector of the Aegean islands were invited to participate. A structured questionnaire was used to collect demographic data and data about their knowledge and attitudes toward vaccinations for migrant and refugees. Results: A total of 120 HCP participated (72 % response rate), including 54 (45 %) physicians, 43 nurses (35.8 %), and 23 health visitors (19.2 %). Sixty-seven (55.8 %) HCP were aware of the national vaccination guidelines. Health visitors had higher rates of knowledge about the national vaccination guidelines, compared with nurses and physicians (87% versus 44,2% and 51,9%; p-value-0.001). Overall, 73 (60.8 %) HCP were aware of vaccinations during the first examination upon arrival. Primary-healthcare physicians were more likely to be aware about the time of vaccine administration compared with hospital-based physicians (74 % versus 50 %; p-value = 0.006). Out of 120 HCP, 45 % knew that vaccination guidelines apply to all newly-arrived migrant and refugees and 65 % that vaccinations are free-of-charge. Overall, 67.5 % of participants supported no serology testing before vaccination, 21.8 % were against free-of-charge vaccinations, and 55 % recommended only priority vaccinations. Conclusions: There is a need to increase HCP' awareness and knowledge through training programs and tailored protocols focusing on vaccinations for newly-arrived migrant and refugee children and adolescents in order to promote effective vaccination of this vulnerable population.

A low-cost open-source imaging platform reveals spatiotemporal insight into leaf elongation and movement.

Plant organs move throughout the diurnal cycle, changing leaf and petiole positions to balance light capture, leaf temperature, and water loss under dynamic environmental conditions. Upward movement of the petiole, called hyponasty, is one of several traits of the shade avoidance syndrome (SAS). SAS traits are elicited upon perception of vegetation shade signals such as far-red light (FR) and improve light capture in dense vegetation. Monitoring plant movement at a high temporal resolution allows studying functionality and molecular regulation of hyponasty. However, high temporal resolution imaging solutions are often very expensive, making this unavailable to many researchers. Here, we present a modular and low-cost imaging setup, based on small Raspberry Pi computers that can track leaf movements and elongation growth with high temporal resolution. We also developed an open-source, semiautomated image analysis pipeline. Using this setup, we followed responses to FR enrichment, light intensity, and their interactions. Tracking both elongation and the angle of the petiole, lamina, and entire leaf in Arabidopsis (Arabidopsis thaliana) revealed insight into R:FR sensitivities of leaf growth and movement dynamics and the interactions of R:FR with background light intensity. The detailed imaging options of this system allowed us to identify spatially separate bending points for petiole and lamina positioning of the leaf.

Mechanodetection of neighbor plants elicits adaptive leaf movements through calcium dynamics.

Plants detect their neighbors via various cues, including reflected light and touching of leaf tips, which elicit upward leaf movement (hyponasty). It is currently unknown how touch is sensed and how the signal is transferred from the leaf tip to the petiole base that drives hyponasty. Here, we show that touch-induced hyponasty involves a signal transduction pathway that is distinct from light-mediated hyponasty. We found that mechanostimulation of the leaf tip upon touching causes cytosolic calcium ([Ca2+]cyt induction in leaf tip trichomes that spreads towards the petiole. Both perturbation of the calcium response and the absence of trichomes reduce touch-induced hyponasty. Finally, using plant competition assays, we show that touch-induced hyponasty is adaptive in dense stands of Arabidopsis. We thus establish a novel, adaptive mechanism regulating hyponastic leaf movement in response to mechanostimulation by neighbors in dense vegetation.

Why did glutamate, GABA, and melatonin become intercellular signalling molecules in plants?

Intercellular signalling is an indispensable part of multicellular life. Understanding the commonalities and differences in how signalling molecules function in two remote branches of the tree of life may shed light on the reasons these molecules were originally recruited for intercellular signalling. Here we review the plant function of three highly studied animal intercellular signalling molecules, namely glutamate, γ-aminobutyric acid (GABA), and melatonin. By considering both their signalling function in plants and their broader physiological function, we suggest that molecules with an original function as key metabolites or active participants in reactive ion species scavenging have a high chance of becoming intercellular signalling molecules. Naturally, the evolution of machinery to transduce a message across the plasma membrane is necessary. This fact is demonstrated by three other well-studied animal intercellular signalling molecules, namely serotonin, dopamine, and acetylcholine, for which there is currently no evidence that they act as intercellular signalling molecules in plants.

Local light signaling at the leaf tip drives remote differential petiole growth through auxin-gibberellin dynamics.

Although plants are immobile, many of their organs are flexible to move in response to environmental cues. In dense vegetation, plants detect neighbors through far-red light perception with their leaf tip. They respond remotely, with asymmetrical growth between the abaxial and adaxial sides of the leafstalk, the petiole. This results in upward movement that brings the leaf blades into better lit zones of the canopy. The plant hormone auxin is required for this response, but it is not understood how non-differential leaf tip-derived auxin can remotely regulate movement. Here, we show that remote signaling of far-red light promotes auxin accumulation in the abaxial petiole. This local auxin accumulation is facilitated by reinforcing an intrinsic directionality of the auxin transport protein PIN3 on the petiole endodermis, as visualized with a PIN3-GFP line. Using an auxin biosensor, we show that auxin accumulates in all cell layers from endodermis to epidermis in the abaxial petiole, upon far-red light signaling in the remote leaf tip. In the petiole, auxin elicits a response to both auxin itself as well as a second growth promoter; gibberellin. We show that this dual regulation is necessary for hyponastic leaf movement in response to light. Our data indicate that gibberellin is required to permit cell growth, whereas differential auxin accumulation determines which cells can grow. Our results reveal how plants can spatially relay information about neighbor proximity from their sensory leaf tips to the petiole base, thus driving adaptive growth.

Water stress resilient cereal crops: Lessons from wild relatives.

Cereal crops are significant contributors to global diets. As climate change disrupts weather patterns and wreaks havoc on crops, the need for generating stress-resilient, high-yielding varieties is more urgent than ever. One extremely promising avenue in this regard is to exploit the tremendous genetic diversity expressed by the wild ancestors of current day crop species. These crop wild relatives thrive in a range of environments and accordingly often harbor an array of traits that allow them to do so. The identification and introgression of these traits into our staple cereal crops can lessen yield losses in stressful environments. In the last decades, a surge in extreme drought and flooding events have severely impacted cereal crop production. Climate models predict a persistence of this trend, thus reinforcing the need for research on water stress resilience. Here we review: (i) how water stress (drought and flooding) impacts crop performance; and (ii) how identification of tolerance traits and mechanisms from wild relatives of the main cereal crops, that is, rice, maize, wheat, and barley, can lead to improved survival and sustained yields in these crops under water stress conditions.

Light signalling shapes plant-plant interactions in dense canopies.

Plants growing at high densities interact via a multitude of pathways. Here, we provide an overview of mechanisms and functional consequences of plant architectural responses initiated by light cues that occur in dense vegetation. We will review the current state of knowledge about shade avoidance, as well as its possible applications. On an individual level, plants perceive neighbour-associated changes in light quality and quantity mainly with phytochromes for red and far-red light and cryptochromes and phototropins for blue light. Downstream of these photoreceptors, elaborate signalling and integration takes place with the PHYTOCHROME INTERACTING FACTORS, several hormones and other regulators. This signalling leads to the shade avoidance responses, consisting of hyponasty, stem and petiole elongation, apical dominance and life cycle adjustments. Architectural changes of the individual plant have consequences for the plant community, affecting canopy structure, species composition and population fitness. In this context, we highlight the ecological, evolutionary and agricultural importance of shade avoidance.

Reducing shade avoidance can improve Arabidopsis canopy performance against competitors.

Plants that grow in high density communities activate shade avoidance responses to consolidate light capture by individuals. Although this is an evolutionary successful strategy, it may not enhance performance of the community as a whole. Resources are invested in shade responses at the expense of other organs and light penetration through the canopy is increased, allowing invading competitors to grow better. Here we investigate if suppression of shade avoidance responses would enhance group performance of a monoculture community that is invaded by a competitor. Using different Arabidopsis genotypes, we show that suppression of shade-induced upward leaf movement in the pif7 mutant increases the pif7 communal performance against invaders as compared to a wild-type canopy. The invaders were more severely suppressed and the community grew larger as compared to wild type. Using computational modelling, we show that leaf angle variations indeed strongly affect light penetration and growth of competitors that invade the canopy. Our data thus show that modifying specific shade avoidance aspects can improve plant community performance. These insights may help to suppress weeds in crop stands.

A Gas-and-Brake Mechanism of bHLH Proteins Modulates Shade Avoidance.

Plants detect proximity of competitors through reduction in the ratio between red and far-red light that triggers the shade avoidance syndrome, inducing responses such as accelerated shoot elongation and early flowering. Shade avoidance is regulated by PHYTOCHROME INTERACTING FACTORs, a group of basic helix-loop-helix (bHLH) transcription factors. Another (b)HLH protein, KIDARI (KDR), which is non-DNA-binding, was identified in de-etiolation studies and proposed to interact with LONG HYPOCOTYL IN FAR-RED1 (HFR1), a (b)HLH protein that inhibits shade avoidance. Here, we established roles of KDR in regulating shade avoidance in Arabidopsis (Arabidopsis thaliana) and investigated how KDR regulates the shade avoidance network. We showed that KDR is a positive regulator of shade avoidance and interacts with several negative growth regulators. We identified KDR interactors using a combination of yeast two-hybrid screening and dedicated confirmations with bimolecular fluorescence complementation. We demonstrated that KDR is translocated primarily to the nucleus when coexpressed with these interactors. A genetic approach confirmed that several of these interactions play a functional role in shade avoidance; however, we propose that KDR does not interact with HFR1 to regulate shade avoidance. Based on these observations, we propose that shade avoidance is regulated by a three-layered gas-and-brake mechanism of bHLH protein interactions, adding a layer of complexity to what was previously known.

Soil Salinity Limits Plant Shade Avoidance.

Global food production is set to keep increasing despite a predicted decrease in total arable land [1]. To achieve higher production, denser planting will be required on increasingly degraded soils. When grown in dense stands, crops elongate and raise their leaves in an effort to reach sunlight, a process termed shade avoidance [2]. Shade is perceived by a reduction in the ratio of red (R) to far-red (FR) light and results in the stabilization of a class of transcription factors known as PHYTOCHROME INTERACTING FACTORS (PIFs) [3, 4]. PIFs activate the expression of auxin biosynthesis genes [4, 5] and enhance auxin sensitivity [6], which promotes cell-wall loosening and drives elongation growth. Despite our molecular understanding of shade-induced growth, little is known about how this developmental program is integrated with other environmental factors. Here, we demonstrate that low levels of NaCl in soil strongly impair the ability of plants to respond to shade. This block is dependent upon abscisic acid (ABA) signaling and the canonical ABA signaling pathway. Low R:FR light enhances brassinosteroid (BR) signaling through BRASSINOSTEROID SIGNALING KINASE 5 (BSK5) and leads to the activation of BRI1 EMS SUPPRESSOR 1 (BES1). ABA inhibits BSK5 upregulation and interferes with GSK3-like kinase inactivation by the BR pathway, thus leading to a suppression of BES1:PIF function. By demonstrating a link between light, ABA-, and BR-signaling pathways, this study provides an important step forward in our understanding of how multiple environmental cues are integrated into plant development.

Neighbor detection at the leaf tip adaptively regulates upward leaf movement through spatial auxin dynamics.

Vegetation stands have a heterogeneous distribution of light quality, including the red/far-red light ratio (R/FR) that informs plants about proximity of neighbors. Adequate responses to changes in R/FR are important for competitive success. How the detection and response to R/FR are spatially linked and how this spatial coordination between detection and response affects plant performance remains unresolved. We show in Arabidopsis thaliana and Brassica nigra that localized FR enrichment at the lamina tip induces upward leaf movement (hyponasty) from the petiole base. Using a combination of organ-level transcriptome analysis, molecular reporters, and physiology, we show that PIF-dependent spatial auxin dynamics are key to this remote response to localized FR enrichment. Using computational 3D modeling, we show that remote signaling of R/FR for hyponasty has an adaptive advantage over local signaling in the petiole, because it optimizes the timing of leaf movement in response to neighbors and prevents hyponasty caused by self-shading.

Flow injection on-line displacement/solid phase extraction system coupled with flame atomic absorption spectrometry for selective trace silver determination in water samples.

A novel flow injection (FI) on-line displacement solid phase extraction preconcentration and/or separation method coupled with FAAS in order to minimize interference from other metals was developed for trace silver determination. The proposed method involved the on-line formation and subsequently pre-sorption of lead diethyldithiocarbamate (Pb-DDTC) into a column packed with PTFE-turnings. The preconcentration and/or separation of the Ag(I) took place through a displacement reaction between Ag(I) and Pb(II) of the pre-sorbed Pb-DDTC. Finally, the retained analyte was eluted with isobutyl methyl ketone (IBMK) and delivered directly to nebulizer for measuring. Interference from co-existing ions with lower DDTC complex stability in comparison with Pb-DDTC, was eliminated without need for any masking reagent. With 120 s of preconcentration time at a sample flow rate of 7.6 mL min(-1), an enhancement factor of 110 and a detection limit (3s) of 0.2 microg L(-1) were obtained. The precision (RSD, n=10) was 3.1% at the 10 mug L(-1) level. The developed method was successfully applied to trace silver determination in a variety of environmental water samples and certified reference material.

Safety and efficacy of manual stepping and overlapping of beta-emitter for diffuse in-stent restenosis lesions.

BACKGROUND: The effects of overlapping beta-emitter sources on the treatment of in-stent restenosis (ISR) lesions as a result of manual stepping are unknown. METHODS AND RESULTS: In the BETA WRIST (Beta Washington Radiation for In-stent Restenosis Trial), 17 out of the 50 patients who received radiation treatment had diffuse ISR in native coronaries that required manual stepping of the beta-emitter (90Y) source in order to cover the lesion and the edges. Fourteen of those patients received radiation with an overlap of up to 3 mm in the middle of the stented segment. The prescribed dose was 20.6 Gy to a distance of 1.0 mm from the surface of the inflated balloon, and the calculated dose to the vessel wall at the overlapped area did not exceed 75 Gy. There was no difference in late total occlusion (7.1% vs. 9.0%, P=NS) and target lesion revascularization (28.5% vs. 27.2%, P=NS) between patients with stepping and those without stepping. At 6 months, there was no evidence of perforation or aneurysm at the overlapped segments. Quantitative coronary angiographic (QCA) analysis revealed significantly reduced late loss in the overlapped segment compared to the adjacent segment (P=.04). Serial (postradiation vs. follow-up) IVUS measurement showed larger mean lumen cross-sectional area (CSA) (P=.0035) and smaller mean intimal hyperplasia (IH) CSA (P=.0010) in the overlapped segment compared to the adjacent segment. CONCLUSION: Manual stepping of beta-emitter source with a short overlapped segment is safe for diffuse ISR. Further increase in lumen dimension and reduction in IH formation are observed at the overlapped segment.