The dynamics of strigolactone perception in Striga hermonthica: a working hypothesis

Plant-derived strigolactones have diverse functions at ecological scale, including effects upon the growth of plants themselves. The parasitic plants from the family Orobanchaceae interfere with the ecological and hormonal functions of strigolactones to generate unique germination abilities based on the sensing of host-derived strigolactones. Although the recent discovery of strigolactone receptors has enabled us to begin elucidating the mechanism of strigolactone perception, how perception relates to plant parasitism is still a mystery. In this review, we explore emerging questions by introducing recent advances in strigolactone research in parasitic plants. We also attempt to construct a conceptual framework for the unique in planta dynamics of strigolactone perception uncovered through the use of fluorescent probes for strigolactone receptors. Understanding the mechanisms of strigolactone-related processes is essential for controlling the parasitic plant Striga hermonthica, which has caused devastating damage to crop production in Africa.

Discovery of Shoot Branching Regulator Targeting Strigolactone Receptor DWARF14

DWARF14 (D14) is a strigolactone receptor that plays a central role in suppression of shoot branching, and hence is a potential target to increase crop productions and biomass. Recently, we reported a fluorescence turn-on probe, Yoshimulactone Green (YLG), which generates a strong fluorescence upon the hydrolysis by D14-type strigolactone receptors. Herein, we applied a YLG-based in vitro assay to a high-throughput chemical screening and identified a novel small molecule DL1 as a potent inhibitor of D14. DL1 competes with endogenous strigolactones, thereby increasing the number of shoot branching in a model plant Arabidopsis as well as in rice. Thus, DL1 is expected to be useful not only as a tool to understand the biological roles of D14 receptors in plant growth and development, but also as a potent agrochemical to improve the crop yield.

Discovery of synthetic small molecules that enhance the number of stomata: C–H functionalization chemistry for plant biology

The first-in-class synthetic small molecules enhancing the number of stomata in Arabidopsis thaliana have been discovered.

Key Structural Elements of Unsymmetrical Cyanine Dyes for Highly Sensitive Fluorescence Turn-On DNA Probes

Unsymmetrical cyanine dyes, such as thiazole orange, are useful for the detection of nucleic acids with fluorescence because they dramatically enhance the fluorescence upon binding to nucleic acids. Herein, we synthesized a series of unsymmetrical cyanine dyes and evaluated their fluorescence properties. A systematic structure-property relationship study has revealed that the dialkylamino group at the 2-position of quinoline in a series of unsymmetrical cyanine dyes plays a critical role in the fluorescence enhancement. Four newly designed unsymmetrical cyanine dyes showed negligible intrinsic fluorescence in the free state and strong fluorescence upon binding to double-stranded DNA (dsDNA) with a quantum yield of 0.53 to 0.90, which is 2 to 3 times higher than previous unsymmetrical cyanine dyes. A detailed analysis of the fluorescence lifetime revealed that the dialkylamino group at the 2-position of quinoline suppressed nonradiative decay in favor of increased fluorescence quantum yield. Moreover, these newly developed dyes were able to stain the nucleus specifically in fixed HeLa cells examined by using a confocal laser-scanning microscope.

PARASITIC PLANTS. Probing strigolactone receptors in Striga hermonthica with fluorescence

Elucidating the signaling mechanism of strigolactones has been the key to controlling the devastating problem caused by the parasitic plant Striga hermonthica. To overcome the genetic intractability that has previously interfered with identification of the strigolactone receptor, we developed a fluorescence turn-on probe, Yoshimulactone Green (YLG), which activates strigolactone signaling and illuminates signal perception by the strigolactone receptors. Here we describe how strigolactones bind to and act via ShHTLs, the diverged family of α/β hydrolase-fold proteins in Striga. Live imaging using YLGs revealed that a dynamic wavelike propagation of strigolactone perception wakes up Striga seeds. We conclude that ShHTLs function as the strigolactone receptors mediating seed germination in Striga. Our findings enable access to strigolactone receptors and observation of the regulatory dynamics for strigolactone signal transduction in Striga.

Development of the crosslinking reactions to RNA triggered by oxidation

In this paper, we have reported a novel oxidation triggered crosslinking nucleobase ATVP (1) and demonstrated that the oxidized form ASVP (2) showed a very fast and selective crosslinking reaction to cytosine in RNA.

The Crosslink formation of 2'-OMe oligonucleotide containing 2-amino-6-vinylpurine protects mRNA from miRNA-mediated silencing

Masking the miRNA binding site: Crosslink-forming oligonucleotide (CFO) was used for target gene-specific inhibition of microRNA (miRNA) functions. This method can interfere with specific miRNA-mRNA interactions by recognizing sequences unique to the 3'-UTR that are inherent in each mRNA.

Synthesis of 6-amino-2-vinylpurine derivatives for cross-linking and evaluation of the reactivity

Oligodeoxynucleotides (ODNs) have been widely used for inhibiting the gene expression in antisense or antigene methods, and the interstrand cross-linking (ICL) forming ODNs have been expected to ensure the inhibition by these methods. Previously, we reported a highly efficient and selective ICL reaction toward cytosine using the 2-amino-6-vinylpurine derivative under acidic conditions. In this Letter, we report the synthesis of ODN containing 6-amino-2-vinylpurine derivatives and evaluation of the cross-linking reactivity.

Morphological and physiological changes of female tropical eels, Anguilla celebesensis and Anguilla marmorata, in relation to downstream migration

The morphological and physiological characteristics of migrating and non-migrating female tropical eels, Anguilla celebesensis and Anguilla marmorata were examined in relation to their downstream migration on central Sulawesi Island, Indonesia. Migrating eels (64 A. celebesensis and 37 A. marmorata) were obtained from weirs set near the outlet area of Poso Lake and non-migrating eels (21 A. celebesensis and 21 A. marmorata) were sampled by set-lines and eel pots in Poso Lake, its inlet rivers, and in the La River system during February 2009 to October 2010. In both species, values of eye index, pectoral-fin length index, gonado-somatic index (I(G)), hepato-somatic index, swimbladder-somatic index and cardio-somatic index of migrating eels were significantly higher than those of non-migrating eels and the gut-somatic index values of the migrating eels were significantly lower than that of non-migrating eels. When silvering stages of eels were classified by the silvering index for Anguilla japonica, in A. celebesensis, all non-migrating eels were Y1 stage and the migrating eels consisted of Y2, S1 and S2 stages eels. In A. marmorata, the non-migrating eels consisted of Y1 and Y2 eels, and the migrating eels consisted of Y2 and S1 eels, but there were no S2 eels. Results of principal component analysis (PCA) of morphological and physiological variables suggested that these characteristics changed drastically between the Y1 and Y2 stages in A. celebesensis, while A. marmorata showed a gradual change with silvering, which differs from the temperate species A. japonica. The mean ±S.D. I(G) value of migrating A. celebesensis (6.9 ± 1.8, 3.3-11.4) was very high and that of A. marmorata (3.1 ± 0.8, 1.8-5.7) was comparatively low. The very different rates of maturation that were found between these two species provide support for the hypothesis that the reproductive characteristics of silver eels can reflect their migration scale.

Production of truncated protein by the crosslink formation of mRNA with 2'-OMe oligoribonucleotide containing 2-amino-6-vinylpurine

The development of convenient methods for controlling the protein expression is an important challenge in the postgenomic era. We applied the crosslink forming oligonucleotide (CFO) as a terminator of the ribosomal translation. In this study, we demonstrated that the improved reactivity of our CFO under physiological conditions enabled the sequence-specific introduction of a steric block for a ribosome on mRNAs. In vitro and in cell translation experiments revealed that the crosslinked mRNA can produce the truncated proteins in which the translation terminates at the desired position.

Alteration of cross-linking selectivity with the 2'-OMe analogue of 2-amino-6-vinylpurine and evaluation of antisense effects

We previously reported that oligodeoxynucleotides containing 2-amino-6-vinylpurine (2-AVP: 1) exhibit efficient selective cross-linking to cytosine. In this study, the 2'-OMe nucleoside analogue (2) of 2-AVP was designed in order to increase its affinity to RNA and enhance metabolic stability. It has been demonstrated that 2'-OMe oligonucleotides bearing 2 achieve highly selective cross-linking to the thymine base in DNA and show higher antisense effect on luciferase production in cell lysate.

Sympatric spawning of Anguilla marmorata and Anguilla japonica in the western North Pacific Ocean

Extensive collections were made of the larvae of the temperate Japanese eel Anguilla japonica and the tropical giant mottled eel Anguilla marmorata in an overlapping area of the North Equatorial Current region of the western North Pacific Ocean. Collections of 189 A. marmorata and > 2500 A. japonica larvae during nine surveys from 1991 to 2007 showed that these two anguillid eels have similar spawning areas just west of the southern West Mariana Ridge. In July to August 2006 and August 2007, morphologically and genetically identified A. marmorata preleptocephali were mainly collected between 14.5-15 degrees N and 142-142.5 degrees E, where A. japonica preleptocephali were also caught in some of the same net tows. Fewer A. marmorata preleptocephali, however, were collected (n = 31) compared to those of A. japonica (n = c. 165), and fewer small larvae of A. marmorata were collected per tow than A. japonica (n = 1-10 and 1-294, respectively), suggesting relatively smaller spawning aggregations of A. marmorata. The distribution of preleptocephali and small larvae was wider in longitude in A. marmorata (131- 143 degrees E) than in A. japonica (137-143 degrees E), while the latitudinal range was almost the same (12-17 degrees N). Although spawning by these two species overlaps both spatially and temporally, the tropical eels of the North Pacific population of A. marmorata probably have a much longer spawning season with fewer spawners, at least in summer, and recruit to a much wider latitudinal range of growth habitats.

Fabrication of gravity-driven microfluidic device

We have studied the micro total analysis system as a blood test. A microfluidic device with a three-pronged microchannel and artificial capillary vessels was fabricated. The microchannel is to transport blood, focus blood cells, and line them up. The vessels are to observe red blood cell deformation. An excimer laser was used to form grooves and so on. Numbers of thermosetting resin film and fluororesin were piled up on a cover glass. A laser fabricated part of the channel at the each film every lamination, and then a three-dimensional structure microchannel was fabricated. The channel sizes have widths of 50-150 microm and depths of 45 mum. Through holes used as artificial capillary vessels are made in the fluororesin having a minimum diameter of 5 microm and a length of 100 microm. As blood and a physiological saline are injected into the microchannel, the device stands upward facing the channel, and blood cells go into the vessels by the force of gravity and sheath flow of the saline. By gravity various groove patterns were made changing the width and length for measurement of blood focusing. Moreover, the red blood cell deformation was observed in the vessels with a microscope.

Systematic synthesis and inhibitory activity of haloacetamidyl oligosaccharide derivatives toward cytoplasmic peptide:N-glycanase

A series of glycosyl haloacetamides were synthesized as potential inhibitors of cytoplasmic peptide:N-glycanase (PNGase), an enzyme that removes N-glycans from misfolded glycoproteins. Chloro-, bromo-, and iodoacetamidyl chitobiose and chitotetraose derivatives exhibited a significant inhibitory activity. No inhibitory activity was observed with of fluoroacetamididyl derivatives. Moreover, N-acetylglucosamine derivatives, beta-chloropropionamidyl chitobiose, and chloroacetamidyl cellooligosaccharide derivatives did not show any activity. These results underscore the importance of the N-acetyl groups of chitobiose for PNGase recognition. In addition, reactivity and position of the leaving group at the reducing end are also important factors.