Untranslated yet indispensable - UTRs act as key regulators in the environmental control of gene expression

To survive and thrive in a dynamic environment, plants must continuously monitor their surroundings and adjust their development and physiology accordingly. Changes in gene expression underlie these developmental and physiological adjustments and are traditionally attributed to widespread transcriptional reprogramming. Growing evidence, however, suggests that post-transcriptional mechanisms also play a vital role in tailoring gene expression to a plant's environment. Untranslated regions (UTRs) act as regulatory hubs for post-transcriptional control, harbouring cis elements that affect an mRNA's processing, localisation, translation and stability and thereby tune the abundance of the encoded protein. Here, we review recent advances made in understanding the critical function UTRs exert in the post-transcriptional control of gene expression in the context of a plant's abiotic environment. We summarise the molecular mechanisms at play, present examples of UTR-controlled signalling cascades and discuss the potential that resides within UTRs to render plants more resilient to a changing climate.</p

Genetic and Biochemical Characterisation of Light Signalling Events during Arabidopsis Seedling and Stomata Development

Plants have evolved a complex regulatory network to perceive and transmit light signals. In Arabidopsis, the COP1/SPA complex acts as a central repressor within this network. It forms part of a ubiquitin ligase that targets activators of the light response for degradation and thereby regulates processes such as seedling development, stomata differentiation, vegetative plant growth and the induction of flowering. But while light signal transduction has been extensively studied over the past decades, light regulation of the COP1/SPA complex is still not fully understood and in some aspects of plant development, additional regulators of the light response are yet to be identified. In the first part of this study, I investigated the role of the SPA proteins within the COP1/SPA complex and their regulation by light. Light controls COP1 nucleocytoplasmic partitioning, but monitoring COP1 subcellular localisation in a spa quadruple mutant showed that its nuclear accumulation in darkness is not changed by the absence of the SPA proteins. However, analysis of protein levels revealed that SPA1 and SPA2 are themselves regulated by rapid, light-induced proteasomal degradation, suggesting that light inactivates COP1/SPA complexes in part by reducing SPA protein levels. SPA2 is more strongly degraded than SPA1, which correlates with the fact that SPA2, but not SPA1, loses its repressor function when seedlings are exposed to light. However, degradation is not the sole reason for the lack of SPA2 function in light-grown seedlings, implying that an additional post-translational mechanism must inactivate the remaining SPA2 protein in the cell. In the second part of this study, I characterised the Aux/IAA protein AXR3, a repressor of auxin signalling, as a novel regulator of light-dependent stomatal development. The axr3-1 gain-of-function mutant displays enhanced stomata formation in darkness, which results from increased cell divisions in the stomatal lineage. Epistasis analysis demonstrated that AXR3 acts genetically upstream of the YDA MAP kinase cascade, but in parallel with COP1, TMM and members of the ER family to regulate stomatal development. Furthermore, this study showed that auxin is required for the suppression of stomata formation in darkness while light appears to counteract its effect. Taken together, these results imply that AXR3 regulates stomatal development in response to light and auxin signals although the mechanism of this regulation remains elusive

Developing a method for customized induction of flowering

<p>Abstract</p> <p>Background</p> <p>The ability to induce flowering on demand is of significant biotechnological interest. FT protein has been recently identified as an important component of the mobile flowering hormone, florigen, whose function is conserved across the plant kingdom. We therefore focused on manipulation of both endogenous and heterologous <it>FT </it>genes to develop a floral induction system where flowering would be inhibited until it was induced on demand. The concept was tested in the model plant <it>Arabidopsis thaliana </it>(Arabidopsis).</p> <p>Results</p> <p>Our starting point was plants with strongly delayed flowering due to silencing of <it>FT </it>with an artificial microRNA directed at <it>FT </it>(<it>amiR-FT</it>) <abbrgrp><abbr bid="B1">1</abbr></abbrgrp>. First, we showed that constitutive expression of a heterologous <it>FT </it>gene (<it>FTa1</it>), from the model legume <it>Medicago truncatula</it>, (Medicago) was able to rescue the <it>amiR-FT </it>late-flowering phenotype. In order to induce flowering in a controlled way, the <it>FTa1 </it>gene was then expressed under the control of an alcohol-inducible promoter in the late flowering <it>amiR-FT </it>plants. Upon exposure to ethanol, <it>FTa1 </it>was rapidly up regulated and this resulted in the synchronous induction of flowering.</p> <p>Conclusions</p> <p>We have thus demonstrated a controlled-inducible flowering system using a novel combination of endogenous and heterologous <it>FT </it>genes. The universal florigenic nature of FT suggests that this type of system should be applicable to crops of economic value where flowering control is desirable.</p

DEK influences the trade-off between growth and arrest via H2A.Z-nucleosomes in Arabidopsis

The decision of whether to grow and proliferate or to restrict growth and develop resilience to stress is a key biological trade-off. In plants, constitutive growth results in increased sensitivity to environmental stress1,2. The underlying mechanisms controlling this decision are however not well understood. We used temperature as a cue to discover regulators of this process in plants, as it both enhances growth and development rates within a specific range and is also a stress at extremes. We found that the conserved chromatin-associated protein DEK plays a central role in balancing the response between growth and arrest in Arabidopsis, and it does this via H2A.Z-nucleosomes. DEK target genes show two distinct categories of chromatin architecture based on the distribution of H2A.Z in +1 nucleosome and gene body, and these predict induction or repression by DEK. We show that these chromatin signatures of DEK target genes are conserved in human cells, suggesting that DEK may act through an evolutionarily conserved mechanism to control the balance between growth and arrest in plants and animals

Building the New Europe: Western and Eastern Roads to Social Partnership

[Excerpt] While the ways in which neoliberalism and economic integration undermine social partnership and the welfare state have been extensively studied, less attention has been given to the ways in which such economic forces may push actors together, in reinvigorated bargaining relationships, to find workable solutions to difficult problems. In his article, we examine the contemporary status of social partnership in four case study countries—Germany, the United Kingdom, Bulgaria and Poland—as well as for Europe as a whole. In the west, while Germany presents a case of established social partnership under pressure, the United Kingdom has stood over the past two decades on the opposite neoliberal side. In the east, Bulgaria is one of the more developed cases of post-communist tripartism, while Poland exemplifies a weaker tripartism that emerged at a later stage of the transformation process. In selecting more and less developed social partnership cases in both west and east, we test the argument that the rise of Thatcher/Reagan/ Friedman ‘free market economics’ is paradoxically driving a resurgence and consolidation of social partnership relations across the new (both western and eastern) Europe

25 Years of thermomorphogenesis research: milestones and perspectives

In 1998, Bill Gray and colleagues showed that warm temperatures trigger arabidopsis hypocotyl elongation in an auxin-dependent manner. This laid the foundation for a vibrant research discipline. With several active members of the 'thermomorphogenesis' community, we here reflect on 25 years of elevated ambient temperature research and look to the future