The shift from terrestrial to aquatic life by whales was a substantial evolutionary event. Here we report the whole-genome sequencing and de novo assembly of the minke whale genome, as well as the whole-genome sequences of three minke whales, a fin whale, a bottlenose dolphin and a finless porpoise. Our comparative genomic analysis identified an expansion in the whale lineage of gene families associated with stress-responsive proteins and anaerobic metabolism, whereas gene families related to body hair and sensory receptors were contracted. Our analysis also identified whale-specific mutations in genes encoding antioxidants and enzymes controlling blood pressure and salt concentration. Overall the whale-genome sequences exhibited distinct features that are associated with the physiological and morphological changes needed for life in an aquatic environment, marked by resistance to physiological stresses caused by a lack of oxygen, increased amounts of reactive oxygen species and high salt levels.

Tigers and their close relatives (Panthera) are some of the world’s most endangered species. Here we report the de novo assembly of an Amur tiger whole-genome sequence as well as the genomic sequences of a white Bengal tiger, African lion, white African lion and snow leopard. Through comparative genetic analyses of these genomes, we find genetic signatures that may reflect molecular adaptations consistent with the big cats’ hypercarnivorous diet and muscle strength. We report a snow leopard-specific genetic determinant in EGLN1 (Met39>Lys39), which is likely to be associated with adaptation to high altitude. We also detect a TYR260G>A mutation likely responsible for the white lion coat colour. Tiger and cat genomes show similar repeat composition and an appreciably conserved synteny. Genomic data from the five big cats provide an invaluable resource for resolving easily identifiable phenotypes evident in very close, but distinct, species.

SummaryDespite the fact that glycine-rich RNA-binding proteins (GRPs) have been implicated in the responses of plants to environmental stresses, their physiological functions and mechanisms of action in stress responses remain largely unknown. Here, we assessed the functional roles of GRP7, one of the eight GRP family members in Arabidopsis thaliana, on seed germination, seedling growth, and stress tolerance under high salinity, drought, or cold stress conditions. The transgenic Arabidopsis plants overexpressing GRP7 under the control of the cauliflower mosaic virus 35S promoter displayed retarded germination and poorer seedling growth compared with the wild-type plants and T-DNA insertional mutant lines under high salinity or dehydration stress conditions. By contrast, GRP7 overexpression conferred freezing tolerance in Arabidopsis plants. GRP7 is expressed abundantly in the guard cells, and has been shown to influence the opening and closing of the stomata, in accordance with the prevailing stress conditions. GRP7 is localized to both the nucleus and the cytoplasm, and is involved in the export of mRNAs from the nucleus to the cytoplasm under cold stress conditions. Collectively, these results provide compelling evidence that GRP7 affects the growth and stress tolerance of Arabidopsis plants under high salt and dehydration stress conditions, and also confers freezing tolerance, particularly via the regulation of stomatal opening and closing in the guard cells.

U12 introns are removed from precursor-mRNA by a U12 intron-specific spliceosome that contains U11 and U12 small nuclear ribonucleoproteins. Although several proteins unique to the U12-type spliceosome have been identified, the manner by which they affect U12-dependent intron splicing as well as plant growth and development remain largely unknown. Here, we assessed the role of U11/U12-31K, a U12-type spliceosomal protein in Arabidopsis thaliana. T-DNA-tagged homozygote lines for U11/U12-31K could not be obtained, and heterozygote mutants were defective for seed maturation, indicating that U11/U12-31K is essential for the normal development of Arabidopsis. Knockdown of U11/U12-31K by artificial microRNA caused a defect in proper U12 intron splicing, resulting in abnormal stem growth and development of Arabidopsis. This defect in proper splicing was not restricted to specific U12-type introns, but most U12 intron splicing was influenced by U11/U12-31K. The stunted inflorescence stem growth was recovered by exogenously applied gibberellic acid (GA), but not by cytokinin, auxin, or brassinosteroid. GA metabolism-related genes were highly downregulated in U11/U12-31K knockdown plants. Importantly, U11/U12-31K was determined to harbor RNA chaperone activity. We propose that U11/U12-31K is an RNA chapereone that is indispensible for proper U12 intron splicing and for normal growth and development of plants.

There are 68 CCCH zinc finger protein genes in the Arabidopsis genome. However, only a few of them have been characerized functionally. In this paper, we report the function of two Arabidopsis CCCH zinc finger proteins AtC3H49/AtTZF3 and AtC3H20/AtTZF2. To investigate their functions, we examined their expression patterns and analyzed their overexpression and knockout(KO)/RNA interference (RNAi) phenotypes. Both AtC3H49/AtTZF3 and AtC3H20/AtTZF2 genes were expressed in various vegetative tissues and in flowers, and their encoded proteins were localized in the cytoplasm. Overexpression of AtC3H49/AtTZF3 or AtC3H20/AtTZF2 conferred ABA hypersensitivity, reduced transpiration and enhanced drought tolerance. Their overexpression also altered the plant growth pattern. The transgenic plants grew slowly during the early stage of growth, but their growth rates were accelerated at later stages, and mature plants were larger than the wild-type plants. Moreover, the transgenic plants displayed delayed senescence and enhanced longevity. Subsequent experiments showed that jasmonic acid (JA)-induced senescence was also delayed. Microarray and quantitative reverse transcription-PCR analyses indicated that the expression of a number of genes involved in JA, ABA and biotic/abiotic stress responses was altered in the transgenic lines. Recombinant AtC3H49/AtTZF3 and AtC3H20/AtTZF2 proteins displayed RNase activity in vitro, suggesting that they may be involved in mRNA turnover process. The knockout/RNAi lines of AtC3H49/AtTZF3 and AtC3H20/AtTZF2 exhibited weak phenotypes, presumably because of their functional redundancy.