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The biomineralization mechanism of mollusc shell has been studied for a long time, but there is a lack of understanding about the relationship between the shell formation in vitro and the signaling system in vivo. In this study, we cloned a novel shell matrix protein gene (hc-temptin), which only be characterized as a water-borne protein pheromone of molluscs in previous studies, from the freshwater mussel Hyriopsis cumingii. By bioinformatics analysis we found that temptin was a gene unique to the clade Lophotrochozoa, and it exists in all mollusc taxa except Cephalopoda. The current data supported the premise that temptin was generated in the early emergence of molluscs and that it maintained a high mutation rate to evolve relative independently. The specificity of hc-temptin expression in the mantle tissue suggests its potential to participate in biomineralization. Its sequence contained typical Ca2+ binding sites. Our experiments involving the pearl formation process, damaged shell repair process, and RNAi experiment showed that hc-temptin was a shell matrix protein that plays an important role in formation of the prismatic layer. The results of this study provided new insights about the origin of the temptin gene and its role in molluscs.

The possible effect of filtered cultures of flagellate Ochromonas sp. on colony formation in M. aeruginosa was investigated in this paper. The results show that filtered cultures of flagellates fed with M. aeruginosa could induce colony formation in M. aeruginosa. Furthermore, induction strength is clearly dependent on the concentration of flagellates and filtered cultures. However, no colonial M. aeruginosa was found in the treatments of filtered cultures of flagellates fed with Microcystis wesenbergii, filtered cultures of flagellate fed with Chlorella pyrenoidosa, and algae homogenates. This suggests that infochemicals released from flagellates fed with M. aeruginosa may be a trigger for colony formation in M. aeruginosa. The clearance rates of flagellates on algae were markedly decreased when they were cultivated with induced colonial M. aeruginosa. These indicate that colony formation in M. aeruginosa is a predator-induced defense which could reduce predation risk from flagellates (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Colonial Microcystis aeruginosa were obtained when the unicellular algae were exposed to flagellate Ochromonas sp. filtrate. To investigate the benefit of this morphological change, flagellates were added into cultures of unicellular and colonial M. aeruginosa, respectively. The clearance rates of flagellates on algae were markedly decreased when they were cultivated with induced colonial M. aeruginosa. This result indicated that colony formation in M. aeruginosa was a predator-induced defense, which could reduce predation risk from flagellate. The increased content of soluble extracellular polysaccharide (sEPS) and bound extracellular polysaccharide (bEPS) may play an important role in adhering M. aeruginosa cells together to form colonies. The decrease of WPS II and the increase of sinking rates of induced colonial M. aeruginosa showed that the costs of grazed-induced colony formation in M. aeruginosa may reflect in the photosystem II efficiency, and in the sinking rates.

In order to monitor the changes of Microcystis along with temporal and spatial variations, seasonal variation of Microcystis in Lake Taihu was investigated by 16S-23S rRNA internal transcribed spacer denaturing gradient gel electrophoresis (16S-23S rRNA-ITS DGGE) and microscopic evaluation. Samples were collected quarterly at four sites (River Mouth, Meiliang Bay, Cross Area, and Lake Center) from August 2006 to April 2007. Results showed that Microcystis dominated total phytoplankton abundance at the four sites in all seasons except winter. The average annual abundance of Microcystis was relatively high at River Mouth and Meiliang Bay, reaching 81.22 x 10(6) and 61.32 x 10(6) cells/L, respectively. For temporal variations, Shannon-Wiener diversity index (H') according to DGGE profile revealed the richness of Microcystis in summer (H' = 1.375 +/- 0.034) and winter (H' = 1.650 +/- 0.032) was lower than that in spring (H' = 2.078 +/- 0.031) and autumn (H' = 2.365 +/- 0.032) (P0.05). While for spatial variations, the richness of Microcystis at River Mouth (H' = 2.015 +/- 0.074) was higher than at other sites during four seasons (P0.01). Very few differences of Microcystis diversity in the same season were observed among the other three sites (P0.05). Canonical correspondence analysis (CCA) was performed to elucidate the relationships between Microcystis operational taxonomic units (OTUs) composition and the environmental factors. Results of CCA revealed that temperature was strongly positively correlated with the first axis (r = 0.963), while TSS was negative correlated with the second axis (r = -0.716). Phylogenetic tree based on the sequencing results of target bands on DGGE gel indicated that samples collected in summer and winter constituted two separated clusters.

The effects of pyrophosphate and polyphosphate on the growth of Microcystis aeruginosa and Chlorella pyrenoidosa were studied in unialgal cultures and in cultures separated by a dialysis membrane. M. aeruginosa and C. pyrenoidosa were able to similarly utilize pyrophosphate and polyphosphate, but their growth rates and cell densities were low in comparison with those in the orthophosphate controls. C. pyrenoidosa had a higher growth rate than M. aeruginosa in both unialgal and the separated cultures; moreover, C. pyrenoidosa had a greater ability to utilize phosphorus than M. qeruginosa. But because the C. pyrenoidosa population developed early but then declined, M. aeruginosa eventually became dominant in the separated cultures. Therefore, the interaction between M. aeruginosa and C. aeruginosa might be complex because of an allelopathy effect, and nutrient competition is not the only factor determining species dominance in the phytoplankton assemblage.

Some characteristics of the rice (Oryza sativa L.) root were found in the experiment of unilaterally irradiating the roots which were planted in water: (i) All the seminal roots, adventitious roots and their branched roots bent away from light, and their curvatures ranged from 25 degrees to 60 degrees . The curvature of adventitious root of the higher node was often larger than that of the lower node, and even larger than that of the seminal root, (ii) The negative phototropic bending of the rice root was mainly due to the larger growth increment of root-tip cells of the irradiated side compared with that of the shaded side, (iii) Root cap was the site of light perception. If root cap was shaded while the root was irradiated the root showed no negative phototropism, and the root lost the characteristic of negative phototropism when root cap was divested. Rice root could resume the characteristic of negative phototropism when the new root cap grew up, if the original cells of root cap were well protected while root cap was divested, (iv) The growth increment and curvature of rice root were both influenced by light intensity. Within the range of 0-100 mumol . m(2) -s(-1), the increasing of light intensity resulted in the decreasing of the growth increment and the increasing of the curvature of rice root, (v) The growth increment and the curvature reached the maximum at 30 degrees C with the temperature treatment of 10-40 degrees C. (vi) Blue-violet light could prominently induce the negative phototropism of rice root, while red light had no such effect. (vii) The auxin (IAA) in the solution, as a very prominent influencing factor, inhibited the growth, the negative phototropism and the gravitropism of rice root when the concentration of IAA increased. The response of negative phototropism of rice root disappeared when the concentration of IAA was above 10 mg . L(-1).

The growth of Microcystis aeruginosa and Chlorella pyrenoidosa in three dissolved organic phosphorus sources (glucose-1- phosphate, adenosine triphosphate, cyclic-adenosine monophosphate) were studied in cultures separated by a dialysis membrane. Results showed that M. aeruginosa and C. pyrenoidosa could utilize those three forms of organic phosphorus, but their growth rates and cell abundances were low in comparison with those in the orthophosphate control. M. aeruginosa had a higher growth rate than C. pyrenoidosa in glucose-1-phosphate, and then became dominate in the separate cultures. In contrast, those two algal species didn’t show any significant differences in the growth rate and cell abundance in the medium with adenosine triphosphate and cyclicadenosine monophosphate. Alkaline phosphatase was an important enzyme for hydrolyzing glucose-1-phosphate, adenosine triphosphate and cyclic-adenosine monophosphate, the activity of which was positively correlated with the growth rate of algae. Considering the big proportion of glucose-1-phosphate in the Lake Taihu, the capability of M. aeruginosa to efficiently utilize this type of organic phosphorus source might be one of reason that why M. aeruginosa is the dominant species in this hyper-eutrophic lake.