Reactivation of hedonic but not sensory representations in human emotional learning

Learning which stimuli in our environment co-occur with painful or pleasurable events is critical for survival. Previous research has established the basic neural and behavioural mechanisms of aversive and appetitive conditioning; however, it is unclear what precisely is learned. Here we examined what aspects of the unconditioned stimulus (US), sensory and hedonic, are transferred to the conditioned stimulus (CS). To decode the content of brain activation patterns elicited during appetitive (soft touch) and aversive (painful touch) conditioning of faces, a novel variation of representational similarity analysis (RSA) based on theoretically driven representational patterns of interest (POIs) was applied to fMRI data. Once face associations were learned through conditioning, globally the CS reactivated US representational patterns showing conditioning dependent reactivation. More specifically, in higher order brain regions, the CS only reactivated hedonic but not sensory aspects of the US, suggesting that affective conditioning primarily carries forward the valence of the experience rather than its sensory origins.

Characterization of a naturally occurring early-flowering rice mutant resulting from a novel variation in the Ghd7 locus

Rice is one of the main staple food crops and is consumed by more than half of the global population. Optimizing the flowering time may help to maximize grain production. In this study, we characterized a rice mutant, Zixiangnuo early-flowering mutant (ZXN-E). Compared with the wild-type variety, Zixiangnuo (ZXN), the mutant plants flowered earlier, were shorter and produced smaller panicles. Bulked segregant analysis revealed a 7-bp deletion in the first exon of the Grain number, plant height, and heading date 7 (Ghd7) locus. The allele with the 7-bp deletion was not detected in the rice varieties included in the 3 000 Rice Genomes Project. Thus, the 7-bp deletion identified in the naturally occurring mutant ZXN-E is a novel variation. Our findings suggest that ZXN-E may be a useful germplasm for breeding new rice varieties.

Extensive transgressive gene expression in a homoploid hybrid species

Hybridization is increasingly recognized as an important evolutionary force contributing novel variation for selection to act on. While mis-expression in F1 hybrids is well documented, how gene expression evolves in stabilized hybrid taxa and contributes novel variation remains an open question, especially for hybrid species without an increase in ploidy. As gene expression evolves in a stabilizing manner, break-up of co-evolved cis- and trans-regulatory elements could lead to transgressive patterns of gene expression in hybrids. Here, we address to what extent gonad gene expression has evolved in an old homoploid hybrid, Italian sparrow, Passer italiae. Through comparing the gene expression of parental species and F1 hybrids to that of the Italian sparrow, we find evidence for strongly transgressive expression in the Italian sparrow, with 22% of the testis genes exhibiting expression patterns outside the range of both parent species, compared to only 0.37% in the F1s. In contrast, Italian sparrow ovary expression was similar to that of one parent species, the house sparrow (P. domesticus). Moreover, the Italian sparrow testis transcriptome is 26.2 -26.6 times as diverged from those of the parent species compared to how divergent their transcriptomes are in spite of it being genetically intermediate. This highlights the potential for regulation of gene expression to produce novel variation following hybridization. Genes involved in energy production and protein synthesis are enriched in the subset that is over-dominantly expressed in Italian sparrow testis, suggesting that selection on key functions have molded the hybrid transcriptome.