Figure 1: Photo from a high altitude location in the Tatra mountains in Slovakia. Research by Lenka Procházková focusses on the local algal snow blooms, which occur notwithstanding exposure to elevated UV doses.

Due to Covid-19, opportunities to meet up, and travel have been severely restricted. As a result, the UV4Plants training school and conference were organized online. The challenge of organising an online conference was accepted by Prof Wolfgang Bilger and Dr Frauke Pescheck with the technical support of the Master’s student Carina Lietz and Christiana Anagnostou, all of them from the University of Kiel, Germany. What was the outcome of undertaking this challenging task? Simply amazing! Using the Zoom and Mattermost platforms, the gap was reduced just to physical distance, since the floor was perfectly set for open, interesting and fruitful discussions, for meeting old colleagues and for finding new ones.

The meeting was preceded by a successful Virtual Training School. The group of 25 participants comprised PhD students and early post-doctoral researchers from different parts of the world. Participants had a shared interest in getting a better insight into the basics of the exciting world of UV radiation and photosynthetic organisms. Each lecture was followed by facultative homework which was always evaluated and opened to discussion the day after. Marcel Jansen introduced the ecological role of UV-B at low doses, highlighting the physiologically relevant differences underlying acclimation, adaptation and stress responses to UV in plants. Henrik Wiegand showed the complexity underlying UV radiation and the basis of the instruments employed for its measurement. Pedro Aphalo provided a detailed description of the light sources used in artificial UV experiments and gave the first insights into the r4photobiology suite, an open source R package for the standardized handling of spectral data. Wolfgang Bilger described the principles and constraints of the instruments used to quantify epidermal UV transmittance and chlorophyll fluorescence. He gave a comprehensive explanation of how to interpret the outputs of these instruments in the context of plant photosynthetic performance. Frauke Pescheck described the different types of UV-induced damage and corresponding repair mechanisms in plants, followed by a step by step methodological description for measuring DNA damage. Éva Hideg showed us the fantastic world of reactive oxygen species (ROS) and the complexity of the (in)direct ROS detection methods used to study their effects in different experimental setups. Hans-Peter Mock introduced us into the history and theory of mass spectrometry, as well as into its application for metabolite analysis with a special focus on UV-screening compounds. The training school therefore provided a basic toolbox for current and incoming researchers to perform studies in the photobiology field.

Once the background was established by the Training School, the international conference of UV4Plants took place during the following week. The event was attended by 125 participants from 30 countries all around the world, including Germany, Czech Republic, Poland, Hungary, Spain, Portugal, Finland, Sweden, UK, Ireland, France, Switzerland, Denmark, Italy, Slovenia, The Netherlands, Japan, Brazil, Argentina, USA, Canada, Republic of Korea, China, New Zealand and Australia. The meeting consisted of six sessions and two discussion panels. Accompanying the programme of lectures, were coffee-breaks, poster sessions and roundtable discussions taking place in breakout rooms, which greatly mitigated for the lack of a face-to-face meeting. The lack of a “classical” conference dinner was creatively compensated for by a musical dinner. Great music from Germany, Poland, Russia, and Ireland was served instead of meals. Each time, the musician joined the meeting for a while and introduced herself/himself. This was an opportunity also to donate money to these artists who are suffering due to the long-term cancellation of concerts in this period. The final point of this scientifically fruitful meeting was a group photo, something that cannot be missed.

No doubt, some of the scientific highlights of the conference will be described in a special issue of Physiologia Plantarum. All participants are welcome to submit their research before (deadline 31-01-2021). Amongst all the exciting research shown, a few selected topics will be mentioned to highlight the diversity of themes covered within the UV4plants. There were the following sessions: UV radiation in the physical environment, Sensing of UV radiation, Functional photoprotection, Acclimation responses to UV radiation, Analytical methods and Application of knowledge. Maxim Durand explored the duration and spectral composition of sunflecks in forest and crop canopies. This is an important area as the ratios of red to far-red and to UV-B are biologically important. In his research, sunfleck properties were shown to be highly canopy-specific, e.g. Picea forest had the highest relative amplitude and sunfleck duration, while forest dominated by Acer was the opposite. The canopy-specific variations in sunfleck properties become even more evident when comparing trees with crops. According to a talk given by Pedro Aphalo, plants differentiate long wave and (majority) short wave UV-A using different photoreceptors (cryptochromes vs. UVR8, respectively) and leading to distinct responses. This means that the UV-A waveband definition is not particularly meaningful from a plant biology perspective. The threshold is at 340 nm which corresponds also with the observed decrease in monomerization of dimeric UVR8 protein. These findings provide a strong support to propose a splitting of the former category of UV-A into UVA1 and UVA2. Paul Barnes summarized the main interplay, and possible consequences, between long-term ozone layer recovery and climate change, including the worldwide economic “Covid-19” shutdown leading to an unusually clear atmosphere. Research by Tadeja Trošt Sedej showed that three alpine species of vascular plants differed in their morphological, biochemical and physiological responses to UV transparent vs. UV reducing filter treatments in the Slovenian Alps, indicating that there are several strategies to thrive successfully at locations with naturally high doses of UV light. Within the analytical methods section, using mass-spectrometry based methods to image the location of different metabolites in plant tissues were described by Hans-Peter Mock. The application of these techniques may enable addressing a current question in the field, which is the location and redistribution of different UV-absorbing metabolites in plant tissues. An interesting application of an UV-B treatment of agricultural crops was presented by Javier Martinéz-Abaigar. Exposure of grapevine skins for two hours to supplemental UV-B resulted in a significant increase in flavonoid content. This increases the quality of the grape skin and the resulting wines. In line with this, Titta Kotilainen showed that despite the effects of changing light spectral quality being well known by the research community, a gap still exists in the transfer and application of this knowledge to plant production environments.

Concerning the posters, we found it interesting the work from Jana Stelzner showing that abiotic factors different from UV-stress and nitrogen deficiency, such as cold temperatures and high light intensities, also induced increased epidermal UV-A absorbance in sunflower leaves. This increase was associated with hydroxycinnamic acid accumulation, rather than to flavonoids which are only present in trace amounts. Interestingly, her results highlight the importance of duration of the UV experiment, since a significant increase in epidermal UV-A absorption was noticed 70 hours, but not 20 hours, after the exposure to stressful abiotic conditions. Alicia Perera-Castro focused on UV-B absorbing compounds in cell walls of mosses from high mountains in Colombia and Livingstone Island (Antarctica). Two phenotypes of Sphagnum magellanicum differed in their net carbon dioxide assimilation rate. The green ones were significantly more photosynthetically active while the red ones accumulated mainly phenolic compounds (UV_280-315). This indicates diffusional limitation and the existence of trade-offs (growth vs. survival) under conditions of high UV exposure and/or desiccation.

Out of the posters and presentations prepared by ESR researchers, four of them, by Zheng Zhou, Aneta Bazant, Laura Díaz-Guerra, and Alicia Perera-Castro, were awarded with 100 Euro bursaries to be used in future UV4Plants events.

To sum up, taking part in the training school and conference was a great pleasure for us! It was a brilliant and perfectly organised event that we can recommend to anybody interested into getting a deeper knowledge about the diverse responses of plants to UV and light. As newcomers in the UV4plants community, it is amazing to witness the evolution of this research field despite the major constraints it faces due to the inherent complexities in manipulating and measuring light, its complex sensing by photosynthetic organisms and the astonishing diversity of the latter in terms of their biology and the environments in which they thrive. From the earliest challenges poised by the ozone layer depletion and thus, studying the UV harmful effects, it is now clear that the role of UV in phototrophs is beyond just being a stressor, having an important role as an environmental regulator (Jansen and Urban, 2019). Currently, the photobiology community is dealing with exciting challenges, one of them being the identification and understanding of the molecular players not only of the spectrum-specific sensing and signal transduction, but also of the crosstalk and commonalities shared with other environmental cues. Who are these molecular players? How do they work? How are these mechanisms conserved in different phototrophs and ecosystems? How can novel model organisms contribute to a better understanding of the wider plant-world? These are intriguing questions being tackled and therefore, future outcomes in photobiology research are something to look forward to.

Lenka Procházková, ORCID:0000-0003-3995-6483

Charles University, Faculty of Science, Prague, Czech Republic

Lenka Procházková is an early-stage post-doc working at the Department of Ecology in the group led by Linda Nedbalová. Lenka did her Doctoral studies on ecophysiology, taxonomy and geographic distribution of snow algae in the same institute. Currently she is studying microbial diversity using high-throughput Illumina sequencing of environmental samples. The focus is on the molecular biology and stress adaptation of cryophiles, in particular snow and glacier ice algae. These microorganisms live under extreme conditions in mountainous habitats, polar snow and glaciers. Lenka presented a poster showing the UV and VIS screening capacity of field collected cysts of Chloromonas krienitzii (Chlorophyta). This microalga was described initially from Japan but research by Lenka and her colleagues showed it to be widespread in the Northern hemisphere.

Adriana Garibay-Hernández, ORCID:0000-0002-5695-356X

Leibniz Institute of Plant Genetics and Crop Plant Research, Gatersleben, Germany

Adriana Garibay-Hernández is an early-stage post-doc working in the Applied Biochemistry group led by Hans-Peter Mock. She did her Doctoral studies on microalgal lipid metabolism under changing environmental conditions at the Universidad Nacional Autónoma de México. One of her current research-interests is the application of mass spectrometry-based approaches to study the diversity, metabolism and physiological roles of phenylpropanoids in crop plants. Adriana gave a talk showing the application of non-targeted metabolomics coupled to genetic analyses to study the genetic basis underlying the role(s) of specific phenylpropanoids in barley agronomic performance.

Reference:

Jansen, Marcel AK and Urban, Otmar (2019) Plant Responses to UV-B Radiation. In: eLS. John Wiley & Sons, Ltd: Chichester. https://doi.org/10.1002/9780470015902.a0027966