Molecular cloning and differential expression of the glucocorticoid receptorgene in the estuarine tapertail anchovy Coilia nasus.

To understand the regulation of the glucocorticoid receptor gene (Gcr) during loading and transport stress in fish, the Gcr gene of Coilia nasus was cloned. Gcr in C. nasus is expressed strongly in the liver and muscle, and less stronglyin the gills, brain, spleen, intestine, trunk kidney, and head kidney. Gcr expression in both the liver and muscle was increased by loading and transport stress. NaCl reduced the death rate caused by loading and transport stress, and the expression of Gcr in liver and muscle differed significantly between the NaCl and non-NaCl groups. To investigate whether the elevated Gcr transcripts were translated into protein, proteins extracted from the liver and muscle were analyzed. In both tissues, C. nasus GCR protein expression patterns paralleled those of Gcr mRNA during stress.

Species delimitation and biogeography of two fir species (Abies) in central China: cytoplasmic DNA variation.

It remains unclear how speciation history might contribute to species-specific variation and affect species delimitation. We examined concordance between cytoplasmic genetic variation and morphological taxonomy in two fir species, Abies chensiensis and A. fargesii, with overlapping distributions in central China. Range-wide genetic variation was investigated using mitochondrial (mt) and plastid (pt) DNA sequences, which contrast in their rates of gene flow. Four mtDNA haplotypes were recovered and showed no obvious species' bias in terms of relative frequency. In contrast, a high level of ptDNA variation was recorded in both species with 3 common ptDNA haplotypes shared between them and 21 rare ptDNA haplotypes specific to one or other species. We argue that the lack of concordance between morphological and molecular variation between the two fir species most likely reflects extensive ancestral polymorphism sharing for both forms of cytoplasmic DNA variation. It is feasible that a relatively fast mutation rate for ptDNA contributed to the production of many species-specific ptDNA haplotypes, which remained rare due to insufficient time passing for their spread and fixation in either species, despite high levels of intraspecific ptDNA gene flow. Our phylogeographic analyses further suggest that polymorphisms in both organelle genomes most likely originated during and following glacial intervals preceding the last glacial maximum, when species distributions became fragmented into several refugia and then expanded in range across central China.