Functional characterisation of Arabidopsis SPL7 conserved protein domains suggests novel regulatory mechanisms in the Cu deficiency response

BACKGROUND: The Arabidopsis SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE (SPL) transcription factor SPL7 reprograms cellular gene expression to adapt plant growth and cellular metabolism to copper (Cu) limited culture conditions. Plant cells require Cu to maintain essential processes, such as photosynthesis, scavenging reactive oxygen species, cell wall lignification and hormone sensing. More specifically, SPL7 activity promotes a high-affinity Cu-uptake system and optimizes Cu (re-)distribution to essential Cu-proteins by means of specific miRNAs targeting mRNA transcripts for those dispensable. However, the functional mechanism underlying SPL7 activation is still to be elucidated. As SPL7 transcript levels are largely non-responsive to Cu availability, post-translational modification seems an obvious possibility. Previously, it was reported that the SPL7 SBP domain does not bind to DNA in vitro in the presence of Cu ions and that SPL7 interacts with a kin17 domain protein to raise SPL7-target gene expression upon Cu deprivation. Here we report how additional conserved SPL7 protein domains may contribute to the Cu deficiency response in Arabidopsis. RESULTS: Cytological and biochemical approaches confirmed an operative transmembrane domain (TMD) and uncovered a dual localisation of SPL7 between the nucleus and an endomembrane system, most likely the endoplasmic reticulum (ER). This new perspective unveiled a possible link between Cu deficit and ER stress, a metabolic dysfunction found capable of inducing SPL7 targets in an SPL7-dependent manner. Moreover, in vivo protein-protein interaction assays revealed that SPL7 is able to homodimerize, probably mediated by the IRPGC domain. These observations, in combination with the constitutive activation of SPL7 targets, when ectopically expressing the N-terminal part of SPL7 including the SBP domain, shed some light on the mechanisms governing SPL7 function. CONCLUSIONS: Here, we propose a revised model of SPL7 activation and regulation. According to our results, SPL7 would be initially located to endomembranes and activated during ER stress as a result of Cu deficiency. Furthermore, we added the SPL7 dimerization in the presence of Cu ions as an additional regulatory mechanism to modulate the Cu deficiency response. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12870-014-0231-5) contains supplementary material, which is available to authorized users

A Conserved KIN17 Curved DNA-Binding Domain Protein Assembles with SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE7 to Adapt Arabidopsis Growth and Development to Limiting Copper Availability

Proper copper (Cu) homeostasis is required by living organisms to maintain essential cellular functions. In the model plant Arabidopsis (Arabidopsis thaliana), the SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE7 (SPL7) transcription factor participates in reprogramming global gene expression during Cu insufficiency in order to improve the metal uptake and prioritize its distribution to Cu proteins of major importance. As a consequence, spl7 null mutants show morphological and physiological disorders during Cu-limited growth, resulting in lower fresh weight, reduced root elongation, and chlorosis. On the other hand, the Arabidopsis KIN17 homolog belongs to a well-conserved family of essential eukaryotic nuclear proteins known to be stress activated and involved in DNA and possibly RNA metabolism in mammals. In the study presented here, we uncovered that Arabidopsis KIN17 participates in promoting the Cu deficiency response by means of a direct interaction with SPL7. Moreover, the double mutant kin17-1 spl7-2 displays an enhanced Cu-dependent phenotype involving growth arrest, oxidative stress, floral bud abortion, and pollen inviability. Taken together, the data presented here provide evidence for SPL7 and KIN17 protein interaction as a point of convergence in response to both Cu deficiency and oxidative stress

Goldilocks and Journal Publication: Finding a Fit That\u27s Just Right

Getting your work published in journals in ways that will help to advance your scholarly record is a complex and multifaceted process. This article is written for early career researchers and graduate and postgraduate students, providing practical advice about what to consider when developing a research and publication profile and establishing yourself within a research community. It explains a range of criteria that are useful to consider when choosing the best journal “fit” for each publication and for your academic trajectory. We hope that considering the elements identified and explained in this article will help you to find a fit that is “just right” for each of your future publications

Exploring the views of students on the use of Facebook in university teaching and learning

Facebook use among students is almost ubiquitous; however, its use for formal academic purposes remains contested. Through an online survey monitoring student use of module Facebook pages and focus groups, this study explores students’ current academic uses of Facebook and their views on using Facebook within university modules. Students reported using Facebook for academic purposes, notably peer–peer communication around group work and assessment – a use not always conceptualised by students as learning. Focus groups revealed that students are not ready or equipped for the collaborative style of learning envisaged by the tutor and see Facebook as their personal domain, within which they will discuss academic topics where they see a strong relevance and purpose, notably in connection with assessment. Students use Facebook for their own mutually defined purposes and a change in student mind- and skill-sets is required to appropriate the collaborative learning benefits of Facebook in formal educational contexts