Separation of magnetic affinity biopolymer adsorbents in a Davis tube magnetic separator

A Davis tube (a matrix-free, flow-through magnetic separator used mainly in mineral processing) has been tested for separation of magnetic affinity biopolymer adsorbents from larger volumes of suspensions. Both magnetic chitosan and magnetic cross-linked erythrocytes could be efficiently separated from litre volumes of suspensions. Up to 90% adsorbent recovery was achieved under optimised separation conditions.     

A Ds-insertion mutant of OSH6 (Oryza sativa Homeobox 6) exhibits outgrowth of vestigial leaf-like structures, bracts, in rice

OSH6 (Oryza sativa Homeobox6) is an ortholog of lg3 (Liguleless3) in maize. We generated a novel allele, termed OSH6-Ds, by inserting a defective Ds element into the third exon of OSH6, which resulted in a truncated OSH6 mRNA. The truncated mRNA was expressed ectopically in leaf tissues and encoded the N-terminal region of OSH6, which includes the KNOX1 and partial KNOX2 subdomains. This recessive mutant showed outgrowth of bracts or produced leaves at the basal node of the panicle. These phenotypes distinguished it from the OSH6 transgene whose ectopic expression led to a “blade to sheath transformation” phenotype at the midrib region of leaves, similar to that seen in dominant Lg3 mutants. Expression of a similar truncated OSH6 cDNA from the 35S promoter (35S::ΔOSH6) confirmed that the ectopic expression of this product was responsible for the aberrant bract development. These data suggest that OSH6-Ds interferes with a developmental mechanism involved in bract differentiation, especially at the basal nodes of panicles. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Role of alternative telomere lengthening unmasked in telomerase knock-out mutant plants

Telomeres in many eukaryotes are maintained by telomerase in whose absence telomere shortening occurs. However, telomerase-deficient Arabidopsis thaliana mutants (Attert ^−/−) show extremely low rates of telomere shortening per plant generation (250–500 bp), which does not correspond to the expected outcome of replicative telomere shortening resulting from ca. 1,000 meristem cell divisions per seed-to-seed generation. To investigate the influence of the number of cell divisions per seed-to-seed generation, Attert ^−/− mutant plants were propagated from seeds coming either from the lower-most or the upper-most siliques (L- and U-plants) and the length of their telomeres were followed over several generations. The rate of telomere shortening was faster in U-plants, than in L-plants, as would be expected from their higher number of cell divisions per generation. However, this trend was observed only in telomeres whose initial length is relatively high and the differences decreased with progressive general telomere shortening over generations. But in generation 4, the L-plants frequently show a net telomere elongation, while the U-plants fail to do so. We propose that this is due to the activation of alternative telomere lengthening (ALT), a process which is activated in early embryonic development in both U- and L-plants, but is overridden in U-plants due to their higher number of cell divisions per generation. These data demonstrate what so far has only been speculated, that in the absence of telomerase, the number of cell divisions within one generation influences the control of telomere lengths. These results also reveal a fast and efficient activation of ALT mechanism(s) in response to the loss of telomerase activity and imply that ALT is probably involved also in normal plant development.     

Diverse mechanisms adopted by fluorescent <Emphasis Type="Italic">Pseudomonas</Emphasis> PGC2 during the inhibition of <Emphasis Type="Italic">Rhizoctonia solani</Emphasis> and <Emphasis Type="Italic">Phytophthora capsici</Emphasis>

Rhizoctonia solani and Phytophthora capsici are two of the most destructive phytopathogens occurring worldwide and are only partly being managed by traditional control strategies. Fluorescent Pseudomonas isolates PGC1 and PGC2 were checked for the antifungal potential against R. solani and P. capsici. Both the isolates were screened for the ability to produce a range of antifungal compounds. The results of this study indicated the role of chitinase and β-1,3-glucanase in the inhibition of R. solani, however, antifungal metabolites of a non-enzymatic nature were responsible for inhibition of P. capsici. The study confirmed that multiple and diverse mechanisms are adopted by the same antagonist to suppress different phytopathogens, as evidenced in case of R. solani and P. capsici.     

Screening and Mutagenesis of Aspergillus niger for the Improvement of Glucose-6-Phosphate Dehydrogenase Production

The Aspergillus niger strain ZBY-7 was selected as the original strain of glucose-6-phosphate dehydrogenase production. After mutagenesis of the strain by means of UV irradiation and nitrosoguanidine, mutants of Aspergillus niger resistant to a certain metabolic inhibitor were obtained. Five of the mutants showed increased glucose-6-phosphate dehydrogenase production. The mutant resistant to antimycin A (Aspergillus niger AM-23) produced the highest level of glucose-6-phosphate dehydrogenase (695.9% of that produced by the original strain).     

Effects of habitat fragmentation on genetic diversity and gene flow among the Homidia socia (Collembola: Entomobryidae) populations in the Thousand Island Lake

In the present study, partial sequences of the mitochondrial cytochrome oxidase subunit I (COI) gene of 22 island populations of the springtail Homidia socia in the Thousand Island Lake were sequenced. Across all sequences, 37 haplotypes were identified for the 510‐bp mitochondrial (mt) DNA COI gene. Haplotype 2 was the most common, and was distributed in the most of the 22 island populations. Haplotype diversity ranged from 0.065 to 0.733, and the total genetic diversity was 0.56216. The genetic characteristics of the 22 island populations were analyzed using the fixation index and gene flow, with values of 0.00043–0.94900 and 0.02703–703.72540, respectively. Comparison between (island area and isolations) with population genetic diversity revealed that there were no significant correlations between them, except for a significant correlation between the number of haplotypes and island area. Mantel tests showed that there was no significant correlation between geographic distance and genetic distance among various groups. All the results indicated that there were no obvious relationships between island characteristics and the genetic diversity of the springtails. We consider that the low dispersal capacity of springtails and the island patches surrounded by water in the Thousand Island Lake are the major factors affecting the genetic diversity of H. socia.