UVB radiation; a specific regulator of the growth and development of Arabidopsis thaliana

Research into the impacts of UVB radiation on plants and ecosystems began in the 1970’s in answer to concerns about the degradation of the stratospheric ozone layer. Early research focused solely on UVB as an agent of plant stress but recently the thinking surrounding UVB has undergone a paradigm shift, now it is seen as a key regulator of plant growth and development. The “UVB response” encompasses a multiplicity of changes in gene expression, metabolism and morphology. A thorough description of the range, complexities and interconnectedness of this response has only begun. The overall aim of this thesis was to explore the functional role the UVB response pathway and attempt to clarify some of the mechanisms behind these. This was achieved using Arabidopsis thaliana as a model system in both indoor and outdoor experiments. It was found that a plants ability to up regulate total soluble phenolics in response to a low dose UVB is potentially more important for UV-protection than accumulation of quercetins and kaempferols that are specifically glycosylated at C-7. Interestingly, the flavonoid glycosylation pattern affected plant morphology. Yet, one of the primary findings of this study was that the UVB induced changes in morphology were transitory. This study also demonstrated the role of UVB radiation and theUVB photoreceptor on morphology and biochemical make-up under changeable, complex, outdoor conditions. It was concluded that a functional UVB photoreceptor is required for optimized plant growth under natural UVB. Evidence of potential practical applications of UVB radiation within the protected cropping industry were also investigated using Lactuca sativa. Based on the findings it is proposed that key plant responses to UVB radiation may be exploitable in the context of improved crop quality and nutritional value

Effects of natural solar UV-B radiation on three Arabidopsis accessions are strongly affected by seasonal weather conditions

Large numbers of studies have reported on the responses of plants that are exposed to a specific dose of ultraviolet-B (UV-B) radiation. However, in the natural environment UV-B is a highly dynamic variable with UV-B intensities depending on, amongst others, geographic, temporal, weather and climatic factors. Furthermore, UV-B effects on plants can potentially be modulated by other environmental variables, and vice versa. This study aimed to characterize UV-B effects on plant morphology and accumulation of UV-screening pigments within the context of an oceanic climate and to assess the potential seasonality of plant UV-B responses. Arabidopsis thaliana was grown outdoors under UV-blocking or transmitting filters. Genotypic differences in the adaptive response to UV-B were assessed at seven time-points over a 12 month period and involved the Arabidopsis accessions Ler, Col-0, and Bur-0. Strong seasonal effects were found on rosette morphology and total UV-screening pigment concentrations across the three accessions. Low temperatures were the main determinant of accumulation of UV-absorbing pigments, with no clear UV-B effect observed at any time throughout the year. There was a significant UV effect on morphology during the summer months, and this was most likely associated with stress. This study shows that UV-effects need to be analysed in the context of weather, and other co-occurring natural factors, and emphasizes the importance of a holistic, multifactorial approach for the investigation of environmentally relevant UV-effects

UV-B induced morphogenesis : four players or a quartet?

Low levels of ultraviolet (UV)-radiation alter the morphology of plants. UV-B exposure can lead to shorter petioles and shorter, narrower and/or thicker leaf blades. The resulting decrease in leaf area has been associated with inhibitory UV-B effects on biomass accumulation. In Arabidopsis, UV-B effects on leaf area have variously been attributed to altered cell division, cell expansion or combinations of these two processes. A dedicated UV-B sensory system, crosstalk between flavonoids and auxins, endoreduplication and generic Stress Induced Morphogenic Responses (SIMR) have all been proposed to contribute to the UV-B phenotype. Here, we propose that UV-mediated morphogenesis, rather than being controlled by a single regulatory pathway, is controlled by a regulatory blur involving multiple compensatory molecular and physiological feedback interactions

P216 Mesenteric disease is directly related to mucosal disease in Crohn\u27s disease.

Crohn’s disease (CD) displays mesenteric disease manifestations such as fat wrapping and mesenteric thickening. The frequency at which these occur in CD point to a pathobiological relevance. Fat wrapping in particular has been suggested to play a role in disease progression [1]. This study aimed to evaluate the relationship between mesenteric disease and other manifestations of CD and to examine the significance of advanced mesenteric disease.ACCEPTEDpeer-reviewe

P071 The mesentery in Crohn\u27s disease displays mesenchymal abnormalities.

Background: Recent advances in our understanding of mesenteric anatomy have shown that the mesentery is continuous along the intestinal tract at vascular, lymphatic and connective tissue levels [1]. Thus, the mesentery represents a conduit which may propagate disease [2]. This study aimed to investigate abnormalities of the mesentery in Crohn\u27s disease (CD) at a histological level.ACCEPTEDpeer-reviewe

P216 Mesenteric disease is directly related to mucosal disease in Crohn's disease.

Crohn’s disease (CD) displays mesenteric disease manifestations such as fat wrapping and mesenteric thickening. The frequency at which these occur in CD point to a pathobiological relevance. Fat wrapping in particular has been suggested to play a role in disease progression [1]. This study aimed to evaluate the relationship between mesenteric disease and other manifestations of CD and to examine the significance of advanced mesenteric disease

P026 The role of fibrocytes in mesenteric Crohn's disease.

The mesentery in Crohn’s disease frequently displays disease manifestations, such as mesenteric thickening and fat wrapping. Fibrocytes are a precursor cell type that can differentiate into fibroblasts or adipocytes [1]. They have previously been identified in the mesentery in inflammatory conditions such as mesenteric panniculitis [2]. This study aimed to investigate the role of fibrocytes in Crohn’s mesenteric disease manifestations