BackgroundThe Chinese mitten crab, Eriocheir sinensis, is one of the most studied and economically important crustaceans in China. Its transition from a swimming to a crawling method of movement during early development, anadromous migration during growth, and catadromous migration during breeding have been attractive features for research. However, knowledge of the underlying molecular mechanisms that regulate these processes is still very limited.FindingsA total of 258.8 gigabases (Gb) of raw reads from whole-genome sequencing of the crab were generated by the Illumina HiSeq2000 platform. The final genome assembly (1.12 Gb), about 67.5 % of the estimated genome size (1.66 Gb), is composed of 17,553 scaffolds (>2 kb) with an N50 of 224 kb. We identified 14,436 genes using AUGUSTUS, of which 7,549 were shown to have significant supporting evidence using the GLEAN pipeline. This gene number is much greater than that of the horseshoe crab, and the annotation completeness, as evaluated by CEGMA, reached 66.9 %.ConclusionsWe report the first genome sequencing, assembly, and annotation of the Chinese mitten crab. The assembled draft genome will provide a valuable resource for the study of essential developmental processes and genetic determination of important traits of the Chinese mitten crab, and also for investigating crustacean evolution.

The present work showed that the inferior melting character of FJWC attributed to the lower WSP, higher TP or protopectins, higher cellulose and hemicellulose than those in the pulp of FJ72-1 at harvest time. Lower expression levels of PG, PME and Cel at harvest time might be associated with the inferior melting character.

No abstract

Roegneria C. Koch is a relatively large polyploid perennial genus with 130 species in the Triticeae, and consisting of the St and Y genomes. There are different opinions about whether Roegneria is an independent genus, or whether it should be included in the genus Elymus L. For many species of Roegneria, their genome constitution and phylogenetic relationship are still unknown. More research about the maternal genome donor of the Roegneria species is needed. To investigate the phylogenetic relationships and maternal genome donor of Roegneria and its affinitive genera, phylogenetic analyses of two chloroplast regions ndhF and trnH–psbA sequences were carried out in this study. The results showed that: (i) Campeiostachys Drobow (StYH) and all Roegneria (StY, StStY) species were scattered with Pseudoroegneria Á. Löve (St) species; (ii) R. sinica Keng, R. schugnanica (Nevski) Nevski, R. seriotina Keng, and Elymus calcicolus (Keng) Á. Löve containing the St genome; (iii) there was differentiation among species of Pseudoroegneria; and (iv) the St genome in diploid, tetraploid, and hexaploid species are divergent. Thus, it is suggested that: (i) Pseudoroegneria served as the maternal genome donor of Roegneria, including four species with unknown genomic constitutions (R. sinica, R. schugnanica, R. seriotina, and E. calcicolus); (ii) species of Roegneria or Pseudoroegneria might serve as the maternal genome donor of Campeiostachys; and (iii) the St genome has undergone differentiation during polyploidization in diploid, tetraploid, and hexaploid species.

The fruit mastication trait of C. reticulata was determined by the proportions of WSP and protopectin as well as lignin content, not by cellulose and hemicellulose contents. Pectin content could be a major contribution to the feeling of mastication trait, while PG and PME exhibited an important role in forming a given mastication trait according to the present results as well as previous results for C. sinensis.