The origin of the turtle body plan remains one of the great mysteries of reptile evolution. The anatomy of turtles is highly derived, which renders it difficult to establish the relationships of turtles with other groups of reptiles. The oldest known turtle, Proganochelys from the Late Triassic period of Germany, has a fully formed shell and offers no clue as to its origin. Here we describe a new 220-million-year-old turtle from China, somewhat older than Proganochelys, that documents an intermediate step in the evolution of the shell and associated structures. A ventral plastron is fully developed, but the dorsal carapace consists of neural plates only. The dorsal ribs are expanded, and osteoderms are absent. The new species shows that the plastron evolved before the carapace and that the first step of carapace formation is the ossification of the neural plates coupled with a broadening of the ribs. This corresponds to early embryonic stages of carapace formation in extant turtles, and shows that the turtle shell is not derived from a fusion of osteoderms. Phylogenetic analysis places the new species basal to all known turtles, fossil and extant. The marine deposits that yielded the fossils indicate that this primitive turtle inhabited marginal areas of the sea or river deltas.

The Bacillus subtilis group comprises eight closely related species that are indistinguishable from one another by 16S rRNA gene sequence analysis. Therefore, the gyrB gene, which encodes the subunit B protein of DNA gyrase, was selected as an alternative phylogenetic marker. To determine whether gyrB gene sequence analysis could be used for phylogenetic analysis and species identification of members of the B. subtilis group, the congruence of gyrB grouping with both 16S rRNA gene sequencing and DNA-DNA hybridization data was evaluated. Ranges of gyrB nucleotide and translated amino acid sequence similarities among the eight type strains were 75.4-95.0 % and 88.5-99.2 %, respectively, whereas 16S rRNA gene sequence similarities were 98.1-99.8 %. Results showed that gyrB gene sequences provide higher resolution than 16S rRNA gene sequences. The classification achieved by gyrB sequence analysis was in agreement with results obtained with DNA-DNA hybridization. It is concluded that the gyrB gene may be an efficient alternative target for identification and taxonomic analysis of members of the B. subtilis group.Bacillus subtilis is a Gram-positive, spore-forming, fermentative, aerobic, rod-shaped bacterium. The Bacillus subtilis group contains the closely related taxa Bacillus subtilis subsp. subtilis (Smith et al., 1964;Nakamura et al., 1999), Bacillus licheniformis (Skerman et al., 1980), Bacillus amyloliquefaciens (Priest et al., 1987), Bacillus atrophaeus (Nakamura, 1989), Bacillus mojavensis (Roberts et al., 1994), Bacillus vallismortis (Roberts et al., 1996), Bacillus subtilis subsp. spizizenii (Nakamura et al., 1999) and Bacillus sonorensis (Palmisano et al., 2001). These taxa can be differentiated from one another by fatty acid composition analysis, restriction digest analysis and DNA-DNA hybridization analysis, but are quite difficult to differentiate by phenotypic characteristics (Roberts et al., 1994;Nakamura et al., 1999).16S rRNA gene sequence analysis is the most commonly used method for identifying bacteria or for constructing bacterial phylogenetic relationships (Woese, 1987;Vandamme et al., 1996;Joung & Cote, 2002); however, its usefulness is limited because of the high percentage of sequence similarity between closely related species (Ash et al., 1991;Martínez-Murcia et al., 1992;Christensen et al., 1998). The use of protein-encoding genes as phylogenetic markers is now a common approach (Yamamoto & Harayama, 1998;Ko et al., 2004;Chelo et al., 2007). Detailed investigations have demonstrated that sequences from protein-encoding genes can accurately predict genome relatedness and may replace DNA-DNA hybridization for species identification and delineation in the future (Stackebrandt et al., 2002;Zeigler, 2003).The gyrB gene encodes the subunit B protein of DNA gyrase, a type II DNA topoisomerase, which plays an essential role in DNA replication and is distributed universally among bacterial species (Watt & Hickson, 1994;Huang, 1996). The rate of molecular evolution inferred from gyrB gene sequences ...

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Background: Aberrant expression of circular RNAs contributes to the initiation and progression of cancers, but the underlying mechanism remains elusive. Methods: RNA-seq and qRT-PCR were performed to screen differential expressed circRNAs between gastric cancer tissues and adjacent normal tissues. Candidate circRNA (circMRPS35) was screened out and validated by qRT-PCR. Cell proliferation and invasion ability were determined by CCK-8 and cell invasion assays. RNA-seq, GO-pathway, RNA pull-down and ChIRP were further applied to search for detailed mechanism. Results: Here, a novel circRNA named circMRPS35, was screened out by RNA-seq in gastric cancer tissues, whose expression is related to clinicopathological characteristics and prognosis in gastric cancer patients. Biologically, circMRPS35 suppresses the proliferation and invasion of gastric cancer cells in vitro and in vivo. Mechanistically, circMRPS35 acts as a modular scaffold to recruit histone acetyltransferase KAT7 to the promoters of FOXO1 and FOXO3a genes, which elicits acetylation of H4K5 in their promoters. Particularly, circMRPS35 specifically binds to FOXO1/3a promoter regions directly. Thus, it dramatically activates the transcription of FOXO1/3a and triggers subsequent response of their downstream target genes expression, including p21, p27, Twist1 and E-cadherin, resulting in the inhibition of cell proliferation and invasion. Moreover, circMRPS35 expression positively correlates with that of FOXO1/3a in gastric cancer tissues. Conclusions: Our findings not only reveal the pivotal roles of circMRPS35 in governing histone modification in anticancer treatment, but also advocate for triggering circMRPS35/KAT7/FOXO1/3a pathway to combat gastric cancer.

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