A CRY-BIC negative-feedback circuitry regulating blue light sensitivity of Arabidopsis.

Cryptochromes are blue light receptors that regulate various light responses in plants. Arabidopsis cryptochrome 1 (CRY1) and cryptochrome 2 (CRY2) mediate blue light inhibition of hypocotyl elongation and long-day (LD) promotion of floral initiation. It has been reported recently that two negative regulators of Arabidopsis cryptochromes, Blue light Inhibitors of Cryptochromes 1 and 2 (BIC1 and BIC2), inhibit cryptochrome function by blocking blue light-dependent cryptochrome dimerization. However, it remained unclear how cryptochromes regulate the BIC gene activity. Here we show that cryptochromes mediate light activation of transcription of the BIC genes, by suppressing the activity of CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1), resulting in activation of the transcription activator ELONGATED HYPOCOTYL 5 (HY5) that is associated with chromatins of the BIC promoters. These results demonstrate a CRY-BIC negative-feedback circuitry that regulates the activity of each other. Surprisingly, phytochromes also mediate light activation of BIC transcription, suggesting a novel photoreceptor co-action mechanism to sustain blue light sensitivity of plants under the broad spectra of solar radiation in nature

Morphology, molecular phylogeny and okadaic acid production of epibenthic Prorocentrum (Dinophyceae) species from the northern South China Sea

Around 30 epibenthic Prorocentrum species have been described, but information about their biogeography is limited. Some species are able to produce okadaic acid (OA) and its derivatives, which are responsible for diarrheic shellfish poisoning (DSP). In the present study, we examined the diversity of epibenthic Prorocentrum in the northern South China Sea by isolating single cells from sand, coral, and macroalgal samples collected from 2012 to 2015. Their morphology was examined using light microscopy and scanning electron microscopy. Among 47 Prorocentrum strains, seven morphospecies were identified as P. lima, P. rhathymum, P. concavum, P. cf. emarginatum, P. fukuyoi, P. cf. maculosum and P. panamense. The latter five species have not been previously reported in Chinese waters, and this is the first record of P. panamense outside its type locality. Partial large subunit (LSU) ribosomal DNA and internal transcribed spacer region sequences were obtained and molecular phylogenetic analysis was carried out using maximum likelihood and Bayesian inference. Chinese P. cf. maculosum strains share 99.5% similarity of LSU sequences with the strain from Cuba (close to the type locality), but Chinese P. lima strains share only 96.7% similarity of LSU sequences with the strain from the type locality. P. cf. emarginatum differs from P. fukuyoi mainly in the presence/absence of marginal pores and they form a well-resolved clade together with P. sculptile. OA was detected in all Chinese strains of P. lima and P. cf. maculosum based on liquid chromatography-mass spectrometry analysis, but dinophysistoxin was produced only by two P. lima strains. Chinese strains of P. concavum, P. rhathymum, and P. panamense do not produce detectable level of OA. Our results support the wide distribution of epibenthic Prorocentrum species and highlight the potential risk of DSP in the northern South China Sea

Cryptic diversity within the harmful dinoflagellate Akashiwo sanguinea in coastal Chinese waters is related to differentiated ecological niches

Blooms of the harmful dinoflagellate Akashiwo sanguinea are responsible for the mass mortality of fish and invertebrates in coastal waters. This cosmopolitan species includes several genetically differentiated clades. Four clonal cultures were established by isolating single cells from Xiamen Harbour (the East China Sea) for morphological and genetic analyses. The cultures displayed identical morphology but were genetically different, thus revealing presence of cryptic diversity in the study area. New details of the apical structure complex of Akashiwo sanguinea were also found. To investigate whether the observed cryptic diversity was related to environmental differentiation, 634 cells were obtained from seasonal water samples collected from 2008 to 2012. These cells were sequenced by single-cell PCR. For comparison with Chinese material, additional large subunit ribosomal DNA sequences were obtained for three established strains from Malaysian and French waters. To examine potential ecological differentiation of the distinct genotypes, growth responses of the studied strains were tested under laboratory conditions at temperatures of 12 °C to 33 °C. These experiments showed four distinct ribotypes of A. sanguinea globally, with the ribotypes A and B co-occuring in Xiamen Harbour. Ribotype A of A. sanguinea was present year-round in Xiamen Harbour, but it only bloomed in the winter and spring, thus corresponding to the winter type. In contrast, A. sanguinea ribotype B bloomed only in the summer, corresponding to the summer type. This differentiation supports the temperature optimum conditions that were established for these two ribotypes in the laboratory. Ribotype A grew better at lower temperatures compared to ribotype B which preferred higher temperatures. These findings support the idea that various ribotypes of A. sanguinea correspond to distinct ecotypes and allopatric speciation occurred in different climatic regions followed by dispersal

Morphological, Genome and Gene Expression Changes in Newly Induced Autopolyploid Chrysanthemum lavandulifolium (Fisch. ex Trautv.) Makino

Autopolyploidy is widespread in higher plants and plays an important role in the process of evolution. The present study successfully induced autotetraploidys from Chrysanthemum lavandulifolium by colchicine. The plant morphology, genomic, transcriptomic, and epigenetic changes between tetraploid and diploid plants were investigated. Ligulate flower, tubular flower and leaves of tetraploid plants were greater than those of the diploid plants. Compared with diploid plants, the genome changed as a consequence of polyploidization in tetraploid plants, namely, 1.1% lost fragments and 1.6% novel fragments occurred. In addition, DNA methylation increased after genome doubling in tetraploid plants. Among 485 common transcript-derived fragments (TDFs), which existed in tetraploid and diploid progenitors, 62 fragments were detected as differentially expressed TDFs, 6.8% of TDFs exhibited up-regulated gene expression in the tetraploid plants and 6.0% exhibited down-regulation. The present study provides a reference for further studying the autopolyploidization role in the evolution of C. lavandulifolium. In conclusion, the autopolyploid C. lavandulifolium showed a global change in morphology, genome and gene expression compared with corresponding diploid