Phototaxis in Cryptomonas sp. under condition suppressing photosynthesis

Effects of 3-(3, 4-dichlorophenyl)-l, 1-dimethylurea (DCMU)on photosynthetic oxygen evolution, respiratory oxygen uptake,phototactic response and swimming rate in Cryptomonas sp. weredetermined and compared. Photosynthetic oxygen evolution wascompletely inhibited in the presence of 10^–5 M DCMU. Thetreatment did not significantly affect the rates of respiratoryoxygen uptake, phototaxis, and swimming, indicating that directparticipation of photosynthesis in the phototaxis of this algacan be ruled out. Wavelength dependency of photosynthetic oxygen evolution wasalso determined in the range of 560 to 700 nm. The rate of photosyntheticoxygen evolution at 680 nm was as high as that at 560 nm, butno phototactic activity was seen at 680 nm although it was maximumat 560 nm. This is consistent with the above conclusion. (Received February 16, 1976; )     

Stereoselective synthesis of 5-O-carbamoylpolyoxamic acid (2-amino-5-O-carbamoyl-2-deoxy-l-xylonic acid

One of the constituents of polyoxin J, 2-amino-5-O-carbamoyl-2-deoxy-l-xylonic acid (3), has been synthesized stereoselectively from l-sorbopyranose. The amino acid function of 3 was formed in the final stage of the synthesis by reduction of the corresponding α-azido carboxylic acid.     

Arabinosylnucleoside 5'-triphosphate inhibits DNA primase of calf thymus

It has been shown that DNA primase activity is tightly associated with 10S DNA polymerase alpha from calf thymus and that the ribonucleotide-dependent DNA synthesis is more sensitive to araCTP than DNA-primed DNA synthesis (Yoshida, S., et al. (1983) Biochim. Biophys. Acta 741, 348-357). Here we measured DNA primase activity using poly(dT) template or M13 bacteriophage single-stranded DNA template and primer RNA synthesis was coupled to the reaction by Escherichia coli DNA polymerase I Klenow fragment. By this method, the primer RNA synthesis can be measured independently of the associating DNA polymerase alpha. Using poly(dT) template, it was found that arabinosyladenine 5'-triphosphate (araATP) strongly inhibited DNA primase in competition with rATP. The apparent Ki for araATP was 21 microM and the ratio of Ki/Km (for rATP) was as low as 0.015. With poly(dI, dT) or M13 DNA, it was shown that araCTP also inhibited DNA primase in the similar manner. Product analysis using [alpha-32P]rATP showed that araATP inhibited the elongation of primer RNA. However, it is not likely that arabinosylnucleotides act as chain-terminators, since incubation of primer RNA with araATP did not abolish its priming activity. From these results, it is suggested that arabinosylnucleotide inhibits the initiation as well as elongation of Okazaki fragments in mammalian cells.     

Environmental DNA analysis shows high potential as a tool for estimating intraspecific genetic diversity in a wild fish population

Environmental DNA (eDNA) analysis has recently been used as a new tool for estimating intraspecific diversity. However, whether known haplotypes contained in a sample can be detected correctly using eDNA‐based methods has been examined only by an aquarium experiment. Here, we tested whether the haplotypes of Ayu fish (Plecoglossus altivelis altivelis) detected in a capture survey could also be detected from an eDNA sample derived from the field that contained various haplotypes with low concentrations and foreign substances. A water sample and Ayu specimens collected from a river on the same day were analysed by eDNA analysis and Sanger sequencing, respectively. The 10 L water sample was divided into 20 filters for each of which 15 PCR replications were performed. After high‐throughput sequencing, denoising was performed using two of the most widely used denoising packages, unoise3 and dada2 . Of the 42 haplotypes obtained from the Sanger sequencing of 96 specimens, 38 (unoise3 ) and 41 (dada2 ) haplotypes were detected by eDNA analysis. When dada2 was used, except for one haplotype, haplotypes owned by at least two specimens were detected from all the filter replications. Accordingly, although it is important to note that eDNA‐based method has some limitations and some risk of false positive and false negative, this study showed that the eDNA analysis for evaluating intraspecific genetic diversity provides comparable results for large‐scale capture‐based conventional methods. Our results suggest that eDNA‐based methods could become a more efficient survey method for investigating intraspecific genetic diversity in the field.     

Survival rate and environmental response of current-year seedlings of the temperate liana Wisteria floribunda across a heterogeneous environment

Journal of Plant Research - Lianas have a huge influence on forest structure and function. However, it is unclear how the surrounding environment affects the establishment of liana seedlings in...     

Proteomic Study to Understand Promotive Effects of Plant-Derived Smoke on Soybean (Glycine max L.) Root Growth Under Flooding Stress

Plant-derived smoke plays a key role in plant growth. Proteomic technique was used for underlying mechanisms of plant-derived smoke on the growth of soybean (Glycine max L.) under flooding stress. The length and weight of soybean root increased with 2000 parts per million plant-derived smoke under flooding stress within 4 days. Altered proteins by plant-derived smoke treatment under flooding stress were mainly related to protein metabolism, stress, and redox. Furthermore, proteins related to mitochondrial electron transport chain decreased by flooding stress; however, they increased by addition of plant-derived smoke under flooding stress. Based on the results of proteomic analysis, confirmation experiments were performed. ATPase abundance and ATP content increased with the treatment of plant-derived smoke under flooding stress. Furthermore, the ascorbate/glutathione cycle was activated with the treatment of plant-derived smoke under flooding stress. These results suggest that plant-derived smoke improves the root growth of soybean with energy production and reactive oxygen scavenging even if it is under flooding stress, which might positively regulate soybean tolerance towards flooding stress.

     

Plant stem cell research is uncovering the secrets of longevity and persistent growth

Plant stem cells have several extraordinary features: they are generated de novo during development and regeneration, maintain their pluripotency, and produce another stem cell niche in an orderly manner. This enables plants to survive for an extended period and to continuously make new organs, representing a clear difference in their developmental program from animals. To uncover regulatory principles governing plant stem cell characteristics, our research project ‘Principles of pluripotent stem cells underlying plant vitality’ was launched in 2017, supported by a Grant-in-Aid for Scientific Research on Innovative Areas from the Japanese government. Through a collaboration involving 28 research groups, we aim to identify key factors that trigger epigenetic reprogramming and global changes in gene networks, and thereby contribute to stem cell generation. Pluripotent stem cells in the shoot apical meristem are controlled by cytokinin and auxin, which also play a crucial role in terminating stem cell activity in the floral meristem; therefore, we are focusing on biosynthesis, metabolism, transport, perception, and signaling of these hormones. Besides, we are uncovering the mechanisms of asymmetric cell division and of stem cell death and replenishment under DNA stress, which will illuminate plant-specific features in preserving stemness. Our technology support groups expand single-cell omics to describe stem cell behavior in a spatiotemporal context, and provide correlative light and electron microscopic technology to enable live imaging of cell and subcellular dynamics at high spatiotemporal resolution. In this perspective, we discuss future directions of our ongoing projects and related research fields.     

Site-directed mutagenesis by biolistic transformation efficiently generates inheritable mutations in a targeted locus in soybean somatic embryos and transgene-free descendants in the T1 generation

The clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated endonuclease 9 (Cas9) system is being rapidly developed for mutagenesis in higher plants. Ideally, foreign DNA introduced by this system is removed in the breeding of edible crops and vegetables. Here, we report an efficient generation of Cas9-free mutants lacking an allergenic gene, Gly m Bd 30K, using biolistic transformation and the CRISPR/Cas9 system. Five transgenic embryo lines were selected on the basis of hygromycin resistance. Cleaved amplified polymorphic sequence analysis detected only two different mutations in e all of the lines. These results indicate that mutations were induced in the target gene immediately after the delivery of the exogenous gene into the embryo cells. Soybean plantlets (T₀ plants) were regenerated from two of the transgenic embryo lines. The segregation pattern of the Cas9 gene in the T₁ generation, which included Cas9-free plants, revealed that a single copy number of transgene was integrated in both lines. Immunoblot analysis demonstrated that no Gly m Bd 30K protein accumulated in the Cas9-free plants. Gene expression analysis indicated that nonsense mRNA decay might have occurred in mature mutant seeds. Due to the efficient induction of inheritable mutations and the low integrated transgene copy number in the T₀ plants, we could remove foreign DNA easily by genetic segregation in the T₁ generation. Our results demonstrate that biolistic transformation of soybean embryos is useful for CRISPR/Cas9-mediated site-directed mutagenesis of soybean for human consumption.