Biology subjects

Tissot, N.

Publications and source records attributed to Tissot, N..

4 recordsLinked to original sources

bioRxiv2024

Photoreceptor-induced sinapate synthesis contributes to photoprotection in Arabidopsis

Plants must balance light capture for photosynthesis with protection from potentially harmful ultraviolet radiation (UV). Photoprotection is mediated by concerted action of photoreceptors, but the underlying molecular mechanisms are not fully understood. In this study, we provide evidence that UV RESISTANCE LOCUS 8 (UVR8) UV-B-, phytochrome red-, and cryptochrome blue-light photoreceptors converge on the induction of FERULIC ACID 5-HYDROXYLASE 1 (FAH1) that encodes a key enzyme in the phenylpropanoid biosynthesis pathway, leading to the accumulation of UV-absorbing sinapate esters. FAH1 induction depends on the bZIP transcription factors ELONGATED HYPOCOTYL 5 (HY5) and HY5-HOMOLOG (HYH) that function downstream of all three photoreceptors. Noticeably, mutants with hyperactive UVR8 signalling rescue fah1 UV sensitivity. Targeted metabolite profiling suggests that this phenotypic rescue is due to the accumulation of UV-absorbing metabolites derived from precursors of sinapate synthesis, namely coumaroyl-glucose and feruloyl-glucose. Our genetic dissection of the phenylpropanoid pathway combined with metabolomic and physiological analyses show that both sinapate esters and flavonoids contribute to photoprotection with sinapates playing a major role for UV screening. Our findings indicate that photoreceptor-mediated regulation of FAH1 and subsequent accumulation of sinapate "sunscreen" compounds is a key protective mechanism to mitigate damage, preserving photosynthetic performance, and ensuring plant survival under UV.

plant biology↗

bioRxiv2024

Sensory perception of fluctuating light in Arabidopsis

When exposed to shade from neighbours, competitive plants modify their growth patterns to improve access to light. In dense plant stands, ranging from forests to humid grasslands and crops, shade is interrupted by sunflecks penetrating the canopy. Relatively infrequent, minute-scale interruptions can significantly contribute to the daily light input. However, given the short duration and the time gap between these low frequency sunflecks (LFS), whether plants can sense them was unknown. Here we show that phytochrome B (phyB), cryptochrome 1 (cry1), cry2, and UV RESISTANCE LOCUS 8 (UVR8) cooperatively perceive LFS to reduce hypocotyl growth in Arabidopsis thaliana. LFS also enhanced the expression of photosynthetic and photo-protective genes and initiated pre-emptive acclimation to water restriction. Repeated LFS increased the nuclear abundance of cry1 and UVR8. This positive feedback enhanced the sensitivity to subsequent LFS and even to the shade between LFS. LFS reduced the nuclear abundance of the growth regulator PHYTOCHROME INTERACTING FACTOR 4 (PIF4), which only slowly recovered upon return to shade, further amplifying the signal. The dynamics of the photo-sensory system under fluctuating light helps adjust plants to the prevailing conditions.

plant biology↗

bioRxiv2022

Long-term population decline of a genetically homogenous continental-wide top Arctic predator

Genetic analysis can provide valuable information for conservation programs by unraveling the demographic trajectory of populations, by estimating effective population size, or by inferring genetic differentiation between populations. Here, we investigated the genetic differentiation within the Snowy Owl (Bubo scandiacus), a species identified as vulnerable by the IUCN, to (i) quantify connectivity among wintering areas, (ii) to evaluate current genetic diversity and effective population size and (iii) to infer changes in the historical effective population size changes from the last millennia to the recent past. The Snowy Owl, a highly mobile top predator, breeds across the Arctic tundra which is a region especially sensitive to current climate change. Using SNP-based analyses on Snowy Owls sampled across the North American nonbreeding range, we found an absence of genetic differentiation among individuals located up to 4,650 km apart. Our results suggest high genetic intermixing and effective dispersal at the continental scale despite documented philopatry to nonbreeding sites in winter. Reconstructing the population demographic indicated that North American Snowy Owls have been steadily declining since the Last Glacial Maximum ca 20,000 years ago and concurrently with global increases in temperature. Conservation programs should now consider North American Snowy Owls as a single, genetically homogenous continental-wide population which is most likely sensitive to the long-term global warming occurring since the Last Glacial Maximum.

ecology↗

bioRxiv2021

The UV RESISTANCE LOCUS 8-Mediated UV-B Response Is Required Alongside CRYPTOCHROME1 For Plant Survival Under Sunlight In The Field

As sessile organisms, plants are subjected to fluctuating sunlight including potentially detrimental ultraviolet-B radiation (UV-B). In Arabidopsis thaliana, experiments under controlled conditions have shown that UV RESISTANCE LOCUS 8 (UVR8) controls photomorphogenic responses for acclimation and tolerance to UV-B; however, its long-term impacts on plant performance remain poorly understood in naturally fluctuating environments. Here we quantified the survival and reproduction of different Arabidopsis mutant genotypes in diverse field and laboratory conditions. We found that uvr8 mutants produced more fruits than wild type in growth chambers with artificial low UV-B conditions but not in natural field conditions. Importantly, independent double mutants of UVR8 and the blue-light photoreceptor gene CRYPTOCHROME 1 (CRY1) in two genetic backgrounds showed a drastic reduction in fitness in the field. UV-B attenuation experiments in field conditions and supplemental UV-B in growth chambers demonstrated that UV-B caused the conditional cry1 uvr8 lethality phenotype. RNA sequencing in different conditions revealed a large number of genes with statistical interaction of UVR8 and CRY1 mutations in the presence of UV-B in the field. Among them, Gene Ontology analysis identified enrichment of categories related to UV-B response, oxidative stress, photoprotection and DNA damage repair. Our study demonstrates the functional importance of the UVR8-mediated response across life stages in natura, which is partially redundant with CRY1, and provides an integral picture of gene expression associated with plant environmental responses under diverse environmental conditions.

plant biology↗