PubMed · 13928913
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J LEBLANC. Peripheral tissue adaptation to cold.. https://pubmed.ncbi.nlm.nih.gov/13928913/
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Understanding the genetic bases and modes of adaptation to current climatic conditions is essential to accurately predict responses to future environmental change. We conducted a genome-wide scan to identify climate-adaptive genetic loci and pathways in the plant Arabidopsis thaliana. Amino acid-changing variants were significantly enriched among the loci strongly correlated with climate, suggesting that our scan effectively detects adaptive alleles. Moreover, from our results, we successfully predicted relative fitness among a set of geographically diverse A. thaliana accessions when grown together in a common environment. Our results provide a set of candidates for dissecting the molecular bases of climate adaptations, as well as insights about the prevalence of selective sweeps, which has implications for predicting the rate of adaptation.
To investigate the possibility that environmental temperature may exert physiologically significant direct, local effects on subcutaneous adipose tissue temperatures, and its secretion of leptin, we exposed healthy males ( n=12) to repeated cold-water immersion (study 1), and also incubated surgically removed human subcutaneous adipose tissue samples ( n=7) at 27 degrees, 32 degrees and 37 degrees C (study 2). In vivo immersions were conducted over 15 days (60-90 min at 18 degrees C). Regional body temperatures and plasma leptin concentrations were measured before and during immersion. Acute cold exposure suppressed plasma leptin concentration (25 min: -14%, 60 min: -22%, P=0.0001), whilst repeated cold-water immersion was associated with an increase of plasma leptin concentration relative to test day 1 (+19% day 8, +13% day 15, overall P=0.03). Leptin secretion in vitro decreased 3.7-fold as the incubation temperature decreased from 37 degrees to 27 degrees C ( P=0.001). In a compartmental model of leptin turnover in vivo, the measured (local) temperature effect on leptin secretion in vitro was more than able to account for the observed cold-induced decrease in leptin concentration in vivo. We therefore conclude that acute and repeated cold-water immersions have separate and opposing effects on circulating leptin concentrations in humans. Under our experimental conditions, the local effects of reduced subcutaneous adipose tissue temperature may be a more important contributor to the acute effects observed in vivo, than the sympathetically mediated suppression of leptin secretion.
Within their natural habitat, plants are subjected to a combination of abiotic conditions that include stresses such as drought and heat. Drought and heat stress have been extensively studied; however, little is known about how their combination impacts plants. The response of Arabidopsis plants to a combination of drought and heat stress was found to be distinct from that of plants subjected to drought or heat stress. Transcriptome analysis of Arabidopsis plants subjected to a combination of drought and heat stress revealed a new pattern of defense response in plants that includes a partial combination of two multigene defense pathways (i.e. drought and heat stress), as well as 454 transcripts that are specifically expressed in plants during a combination of drought and heat stress. Metabolic profiling of plants subjected to drought, heat stress, or a combination of drought and heat stress revealed that plants subject to a combination of drought and heat stress accumulated sucrose and other sugars such as maltose and glucose. In contrast, Pro that accumulated in plants subjected to drought did not accumulate in plants during a combination of drought and heat stress. Heat stress was found to ameliorate the toxicity of Pro to cells, suggesting that during a combination of drought and heat stress sucrose replaces Pro in plants as the major osmoprotectant. Our results highlight the plasticity of the plant genome and demonstrate its ability to respond to complex environmental conditions that occur in the field.