The Arabidopsis Mediator complex subunits MED16, MED14 and MED2 regulate Mediator and RNA polymerase II recruitment to CBF-responsive cold-regulated genes

The Mediator16 (MED16; formerly termed SENSITIVE TO FREEZING6 [SFR6]) subunit of the plant Mediator transcriptional coactivator complex regulates cold-responsive gene expression in Arabidopsis thaliana, acting downstream of the C-repeat binding factor (CBF) transcription factors to recruit the core Mediator complex to cold-regulated genes. Here, we use loss-of-function mutants to show that RNA polymerase II recruitment to CBF-responsive cold-regulated genes requires MED16, MED2, and MED14 subunits. Transcription of genes known to be regulated via CBFs binding to the C-repeat motif/drought-responsive element promoter motif requires all three Mediator subunits, as does cold acclimation–induced freezing tolerance. In addition, these three subunits are required for low temperature–induced expression of some other, but not all, cold-responsive genes, including genes that are not known targets of CBFs. Genes inducible by darkness also required MED16 but required a different combination of Mediator subunits for their expression than the genes induced by cold. Together, our data illustrate that plants control transcription of specific genes through the action of subsets of Mediator subunits; the specific combination defined by the nature of the stimulus but also by the identity of the gene induced

The Mediator subunit SFR6/MED16 controls defence gene expression mediated by salicylic acid and jasmonate responsive pathways

Arabidopsis SENSITIVE TO FREEZING6 (SFR6) controls cold- and drought-inducible gene expression and freezing- and osmotic-stress tolerance. Its identification as a component of the MEDIATOR transcriptional co-activator complex led us to address its involvement in other transcriptional responses. • Gene expression responses to Pseudomonas syringae, ultraviolet-C (UV-C) irradiation, salicylic acid (SA) and jasmonic acid (JA) were investigated in three sfr6 mutant alleles by quantitative real-time PCR and susceptibility to UV-C irradiation and Pseudomonas infection were assessed. • sfr6 mutants were more susceptible to both Pseudomonas syringae infection and UV-C irradiation. They exhibited correspondingly weaker PR (pathogenesis-related) gene expression than wild-type Arabidopsis following these treatments or after direct application of SA, involved in response to both UV-C and Pseudomonas infection. Other genes, however, were induced normally in the mutants by these treatments. sfr6 mutants were severely defective in expression of plant defensin genes in response to JA; ectopic expression of defensin genes was provoked in wild-type but not sfr6 by overexpression of ERF5. • SFR6/MED16 controls both SA- and JA-mediated defence gene expression and is necessary for tolerance of Pseudomonas syringae infection and UV-C irradiation. It is not, however, a universal regulator of stress gene transcription and is likely to mediate transcriptional activation of specific regulons only.</p

Robot pressure : the impact of robot eye gaze and lifelike bodily movements upon decision-making and trust

Between people, eye gaze and other forms of nonverbal communication can influence trust. We hypothesised similar effects would occur during human-robot interaction, predicting a humanoid robot’s eye gaze and lifelike bodily movements (eye tracking movements and simulated “breathing”) would increase participants’ likelihood of seeking and trusting the robot’s opinion in a cooperative visual tracking task. However, we instead found significant interactions between robot gaze and task difficulty, indicating that robot gaze had a positive impact upon trust for difficult decisions and a negative impact for easier decisions. Furthermore, a significant effect of robot gaze was found on task performance, with gaze improving participants’ performance on easy trials but hindering performance on difficult trials. Participants also responded significantly faster when the robot looked at them. Results suggest that robot gaze exerts “pressure” upon participants, causing audience effects similar to social facilitation and inhibition. Lifelike bodily movements had no significant effect upon participant behaviour