Phenotypic flexibility of thermogenesis in the hwamei (Garrulax canorus): responses to cold acclimation.

Cold acclimation in birds involves a comprehensive array of physiological and morphological adjustment ranging from changes in aerobic enzyme activity to metabolic rate and organ mass. In the present study, we investigated phenotypic variation in thermogenic activity in the hwamei (Garrulax canorus) under normal (35°C) or cold (15°C) ambient temperature conditions. Acclimation to an ambient temperature of 15°C for 4 wk significantly increased the body mass, basal metabolic rate (BMR), and energy intake, including both gross energy intake and digestible energy intake, compared with birds kept at 35°C. Furthermore, birds acclimated to 15°C increased the dry mass of their liver and kidneys, but not their heart and pectoral muscles, and displayed higher state-4 respiration in the liver, kidneys, heart, and pectoral muscles, and higher cytochrome-c oxidase (COX) activity in liver, kidney, and pectoral muscle, compared with those kept at 35°C. There was a positive correlation between BMR and state-4 respiration in all of the above organs except the liver, and between BMR and COX activity in all of the above organs. Taken together, these data illustrate the morphological, physiological, and enzymatic changes associated with cold acclimation, and support the notion that the hwamei is a bird species from temperate climates that exhibits high phenotypic flexibility of thermogenic capacity.

Seasonal variation in body mass, body temperature and thermogenesis in the Hwamei, Garrulax canorus.

The basal thermogenesis of birds is beginning to be viewed as a highly flexible physiological trait influenced by environmental fluctuations, particularly changes in ambient temperature (Ta). Many birds living in regions with seasonal fluctuations in Ta typically respond to cold by increasing their insulation and adjusting their metabolic rate. To understand these metabolic adaptations, body temperature (Tb), metabolic rate (MR), thermal neutral zone (TNZ) and thermal conductance were measured within a range of temperatures from 5 to 40°C in free-living Hwamei, Garrulax canorus, in both winter and summer. Body mass was 61.2±0.3g in winter and 55.5±1.0g in summer, and mean Tb was 41.6±0.1°C in winter and 42.3±0.1°C in summer. TNZ was between 28.3 and 35.1°C in winter and between 28.7 and 33.2°C in summer. The mean basal metabolic rate (BMR) within TNZ was 203.32±11.81ml O2 h(-1) in winter and 168.99±6.45ml O2 h(-1) in summer. Minimum thermal conductance was 3.73±0.09joulesg(-1)h(-1)°C(-1) in winter and 3.26±0.06joulesg(-1)h(-1)°C(-1) in summer. Birds caught in winter had higher body mass, MR, and more variable TNZ than those in summer. The increased winter BMR indicates improved ability to cope with cold and maintenance of a high Tb. These results show that the Hwamei's metabolism is not constant, but exhibits pronounced seasonal phenotypic flexibility associated with maintenance of a high Tb.

Genomic Features of Open Chromatin Regions (OCRs) in Wild Soybean and Their Effects on Gene Expressions.

Transcription activation is tightly associated with the openness of chromatin, which allows direct contact between transcriptional regulators, such as transcription factors, and their targeted DNA for downstream gene activation. However, the annotation of open chromatin regions (OCRs) in the wild soybean (Glycine soja) genome is limited. We performed assay for transposase-accessible chromatin using sequencing (ATAC-seq) and successfully identified 22,333 OCRs in the leaf of W05 (a wild soybean accession). These OCRs were enriched in gene transcription start sites (TSS) and were positively correlated with downstream gene expression. Several known transcription factor (TF)-binding motifs were also enriched at the OCRs. A potential regulatory network was constructed using these transcription factors and the OCR-marked genes. Furthermore, by overlapping the OCR distribution with those of histone modifications from chromatin immunoprecipitation followed by sequencing (ChIP-seq), we found that the distribution of the activation histone mark, H3K4me3, but not that of the repressive H3K27me3 mark, was closely associated with OCRs for gene activation. Several putative enhancer-like distal OCRs were also found to overlap with LincRNA-encoding loci. Moreover, our data suggest that homologous OCRs could potentially influence homologous gene expression. Hence, the duplication of OCRs might be essential for plant genome architecture as well as for regulating gene expression.

Effects of temperature acclimation on body mass and energy budget in the Chinese bulbul Pycnonotus sinensis.

Chinese bulbuls (Pycnonotus sinensis) are small passerine birds that inhabit areas of central, southern and eastern China. Previous observations suggest that free-living individuals of this species may change their food intake in response to seasonal changes in ambient temperature. In the present study, we randomly assigned Chinese bulbuls to either a 30℃ or 10℃ group, and measured their body mass (BM), body temperature, gross energy intake (GEI), digestible energy intake (DEI), and the length and mass of their digestive tracts over 28 days of acclimation at these temperatures. As predicted, birds in the 30℃ group had lower body mass, GEI and DEI relative to those in the 10℃ group. The length and mass of the digestive tract was also lower in the 30℃ group and trends in these parameters were positively correlated with BM, GEI and DEI. These results suggest that Chinese bulbuls reduced their absolute energy demands at relatively high temperatures by decreasing their body mass, GEI and DEI, and digestive tract size.