SummaryPre-harvest sprouting (PHS) or vivipary in cereals is an important agronomic trait that results in significant economic loss. A considerable number of mutations that cause PHS have been identified in several species. However, relatively few viviparous mutants in rice (Oryza sativa L.) have been reported. To explore the mechanism of PHS in rice, we carried out an extensive genetic screening and identified 12 PHS mutants (phs). Based on their phenotypes, these phs mutants were classified into three groups. Here we characterize in detail one of these groups, which contains mutations in genes encoding major enzymes of the carotenoid biosynthesis pathway, including phytoene desaturase (OsPDS), f-carotene desaturase (OsZDS), carotenoid isomerase (OsCRTISO) and lycopene b-cyclase (b-OsLCY), which are essential for the biosynthesis of carotenoid precursors of ABA. As expected, the amount of ABA was reduced in all four phs mutants compared with that in the wild type. Chlorophyll fluorescence analysis revealed the occurrence of photoinhibition in the photosystem and decreased capacity for eliminating excess energy by thermal dissipation. The greatly increased activities of reactive oxygen species (ROS) scavenging enzymes, and reduced photosystem (PS) II core proteins CP43, CP47 and D1 in leaves of the Oscrtiso/phs3-1mutant and OsLCY RNAi transgenic rice indicated that photo-oxidative damage occurred in PS II, consistent with the accumulation of ROS in these plants. These results suggest that the impairment of carotenoid biosynthesis causes photo-oxidation and ABA-deficiency phenotypes, of which the latter is a major factor controlling the PHS trait in rice.

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Selenium is an important trace element that occurs in proteins in the form of selenocysteine (Sec) and in tRNAs in the form of selenouridine. Recent large-scale metagenomics projects provide an opportunity for understanding global trends in trace element utilization. Herein, we characterized the selenoproteome of the microbial marine community derived from the Global Ocean Sampling (GOS) expedition. More than 3,600 selenoprotein gene sequences belonging to 58 protein families were detected, including sequences representing 7 newly identified selenoprotein families, such as homologs of ferredoxin–thioredoxin reductase and serine protease. In addition, a new eukaryotic selenoprotein family, thiol reductase GILT, was identified. Most GOS selenoprotein families originated from Cys-containing thiol oxidoreductases. In both Pacific and Atlantic microbial communities, SelW-like and SelD were the most widespread selenoproteins. Geographic location had little influence on Sec utilization as measured by selenoprotein variety and the number of selenoprotein genes detected; however, both higher temperature and marine (as opposed to freshwater and other aquatic) environment were associated with increased use of this amino acid. Selenoproteins were also detected with preference for either environment. We identified novel fusion forms of several selenoproteins that highlight redox activities of these proteins. Almost half of Cys-containing SelDs were fused with NADH dehydrogenase, whereas such SelD forms were rare in terrestrial organisms. The selenouridine utilization trait was also analyzed and showed an independent evolutionary relationship with Sec utilization. Overall, our study provides insights into global trends in microbial selenium utilization in marine environments.

Metazoans use diverse and rapidly evolving mechanisms to determine sex. In Drosophila melanogaster an X-chromosome-counting mechanism determines the sex of an individual by regulating the master switch gene, Sex-lethal (Sxl). The X-chromosome dose is communicated to Sxl by a set of X-linked signal elements (XSEs), which activate transcription of Sxl through its 'establishment' promoter, SxlPe. Here we describe a new XSE called sisterlessC (sisC) whose mode of action differs from that of previously characterized XSEs, all of which encode transcription factors that activate SxlPe directly. In contrast, sisC encodes a secreted ligand for the Drosophila Janus kinase (JAK) and 'signal transducer and activator of transcription' (STAT) signal transduction pathway and is allelic to outstretched (os, also called unpaired). We conclude that sisC works indirectly on Sxl through this signalling pathway because mutations in sisC or in the genes encoding Drosophila JAK or STAT reduce expression of SxlPe similarly. The involvement of os in sex determination confirms that secreted ligands can function in cell-autonomous processes. Unlike sex signals for other organisms, sisC has acquired its sex-specific function while maintaining non-sex-specific roles in development, a characteristic that it shares with all other Drosophila XSEs.

Cross-language transfer of awareness of the structure of compound words was investigated among native speakers of Chinese who were learning English as a second language. Chinese fifth graders received instruction in the morphology of four types of compound words in either Chinese or English. They then completed both the Chinese and English versions of a compound word structure analogy task. Compared with children who received no instruction, children who received instruction in Chinese were able to transfer knowledge they had acquired of compound types in Chinese to comparable types in English. Reverse transfer from English to Chinese was found among children with high reading proficiency.

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The genetic diversity and population genetic structure of the small yellow croaker (Larimichthys polyactis) were investigated. One hundred and fourteen individuals were sampled from 8 localities of the Yellow Sea and the northern East China Sea. Genetic variation in DNA sequences were examined from the first hypervariable region (HVR-1) of the mitochondrial DNA control region. High levels of haplotype diversity (h=0.98±0.87%) in the HVR-1 region were detected, indicating a high level of genetic diverstiy. A total of 84 polymorphic sites were found, and 87 haplotypes were defined. The pairwise nucleotide differences between samples ranged from 3.83±2.19 to 6.56±3.25. The demographic history of L. polyactis was examined by using neutrality tests and mismatch distribution analysis, which indicated a Pleistocene population expansion at about 49,300-197,000 years. The star burst structure of the minimum spanning tree also suggestted a very recent origin for most haplotypes. Hierarchical molecular variance analysis (AMOVA) and conventional population Fst comparisons revealed no significant genetic structure throughout the examined range, which is inconsistent with previous findings based on the morphological and ecological studies. Long-term dispersal and high gene flow likely have contributed to the genetically homogeneous population structure of the species. The knowledge on genetic diversity and genetic structure will be crucial to establish appropriate fishery management stocks for the species.