(+)-Strigol,a witchweed seed germination stimulant,from Menispermum dauricum root culture

(+)-Strigol was isolated from Menispermum dauricum root culture filtrate. Its identity was confirmed by HPLC, 1H NMR, UV and MS, and on the basis of its CD spectrum. This is the first report on isolation of strigolactone from aseptic plant culture.     

Two lignan dimers from bamboo stems (Phyllostachys edulis)

Phyllostadimers A and B, two bis-lignans in which the two lignan units are directly connected by a C-C bond, were isolated from stems of bamboo, Phyllostachys edulis. Their structures were determined on the basis of spectral evidence. In addition, 14 known compounds were also obtained throughout the investigation. Phyllostadimer A significantly inhibited liposomal lipid peroxidation.     

Possible involvement of leaf gibberellins in the clock-controlled expression of XSP30, a gene encoding a xylem sap lectin, in cucumber roots

Root-produced organic compounds in xylem sap, such as hormones and amino acids, are known to be important in plant development. Recently, biochemical approaches have revealed the identities of several xylem sap proteins, but the biological functions and the regulation of the production of these proteins are not fully understood. XYLEM SAP PROTEIN 30 kD (XSP30), which is specifically expressed in the roots of cucumber (Cucumis sativus), encodes a lectin and is hypothesized as affecting the development of above-ground organs. In this report, we demonstrate that XSP30 gene expression and the level of XSP30 protein fluctuate in a diurnal rhythm in cucumber roots. The rhythmic gene expression continues for at least two or three cycles, even under continuous light or dark conditions, demonstrating that the expression of this gene is controlled by a circadian clock. Removal of mature leaves or treatment of shoots with uniconazole-P, an inhibitor of gibberellic acid (GA) biosynthesis, dampens the amplitude of the rhythmic expression; the application of GA negates these effects. These results suggest that light signals perceived by above-ground organs, as well as GA that is produced, possibly, in mature leaves, are important for the rhythmic expression of XSP30 in roots. This is the first demonstration of the regulation of the expression of a clock-controlled gene by GA.     

Role of SODD in regulation of tumor necrosis factor responses

Signaling from tumor necrosis factor receptor type 1 (TNFR1) can elicit potent inflammatory and cytotoxic responses that need to be properly regulated. It was suggested that the silencer of death domains (SODD) protein constitutively associates intracellularly with TNFR1 and inhibits the recruitment of cytoplasmic signaling proteins to TNFR1 to prevent spontaneous aggregation of the cytoplasmic death domains of TNFR1 molecules that are juxtaposed in the absence of ligand stimulation. In this study, we demonstrate that mice lacking SODD produce larger amounts of cytokines in response to in vivo TNF challenge. SODD-deficient macrophages and embryonic fibroblasts also show altered responses to TNF. TNF-induced activation of NF-kappaB is accelerated in SODD-deficient cells, but TNF-induced c-Jun N-terminal kinase activity is slightly repressed. Interestingly, the apoptotic arm of TNF signaling is not hyperresponsive in the SODD-deficient cells. Together, these results suggest that SODD is critical for the regulation of TNF signaling.     

An in vitro evolved precursor tRNA with aminoacylation activity

A set of catalysts for aminoacyl-tRNA synthesis is an essential component for translation. The RNA world hypothesis postulates that RNA catalysts could have played this role. Here we show an in vitro evolved precursor tRNA consisting of two domains, a catalytic 5'-leader sequence and an aminoacyl-acceptor tRNA. The 5'-leader sequence domain selectively self-charges phenylalanine on the 3'-terminus of the tRNA domain. This cis-acting ribozyme is susceptible to RNase P RNA, generating the corresponding 5'-leader segment and the mature tRNA. Moreover, the 5'-leader segment is able to aminoacylate the mature tRNA in trans. Mutational studies have revealed that C(74) and C(75) at the tRNA aminoacyl-acceptor end form base pairs with G71 and G70 of the trans-acting ribozyme. Such Watson-Crick base pairing with tRNA has been observed in RNase P RNA and 23S rRNA, suggesting that all three ribozymes use a similar mechanism for the recognition of the aminoacyl-acceptor end. Our demonstrations indicate that catalytic precursor tRNAs could have provided the foundations for the genetic coding system in the proto-translation system.     

Double-labeled donor probe can enhance the signal of fluorescence resonance energy transfer (FRET) in detection of nucleic acid hybridization

A set of fluorescently-labeled DNA probes that hybridize with the target RNA and produce fluorescence resonance energy transfer (FRET) signals can be utilized for the detection of specific RNA. We have developed probe sets to detect and discriminate single-strand RNA molecules of plant viral genome, and sought a method to improve the FRET signals to handle in vivo applications. Consequently, we found that a double-labeled donor probe labeled with Bodipy dye yielded a remarkable increase in fluorescence intensity compared to a single-labeled donor probe used in an ordinary FRET. This double-labeled donor system can be easily applied to improve various FRET probes since the dependence upon sequence and label position in enhancement is not as strict. Furthermore this method could be applied to other nucleic acid substances, such as oligo RNA and phosphorothioate oligonucleotides (S-oligos) to enhance FRET signal. Although the double-labeled donor probes labeled with a variety of fluorophores had unexpected properties (strange UV-visible absorption spectra, decrease of intensity and decay of donor fluorescence) compared with single-labeled ones, they had no relation to FRET enhancement. This signal amplification mechanism cannot be explained simply based on our current results and knowledge of FRET. Yet it is possible to utilize this double-labeled donor system in various applications of FRET as a simple signal-enhancement method.     

Postextrasystolic contractile decay always contains exponential and alternans components in canine heart

In isolated, blood-perfused canine hearts, postextrasystolic potentiation (PESP) decays monotonically after a noncompensatory pause following a spontaneous extrasystole (ES). The monotonic PESP decay yields myocardial internal Ca(2+) recirculation fraction (RF). We have found that after a compensatory pause (CP), PESP decays in alternans, consisting of an exponential and a sinusoidal decay component. We have proposed that this exponential component also yields RF. In the present study, we examined the reliability of this alternative method by widely changing the ES coupling interval (ESI), CP, and heart rate in the canine excised, cross-circulated left ventricle. We found that all PESP decays consisted of the sum of an exponential and a sinusoidal decay component of variable magnitudes whether a CP existed or not. Their decay constants as well as the calculated RF were independent of the ESI and CP. This confirmed the utility of our alternative RF determination method regardless of the ESI, CP, and heart rate. Direct experimental evidence of Ca(2+) dynamics supportive of this alternative method, however, remains to be obtained.