Genetic architecture underlying the evolutionary change of competitive ability in Asian cultivated and wild rice

Breeding of competitive cultivars has long been fraught with difficulty owing to limited knowledge of the genetic basis of competitive ability. In this study, we examined the diversity of competitive ability in Asian rice and the genetic basis of this variation. Cultivated strains and wild perennial strains have higher competitive ability than wild annual strains. Quantitative trait locus (QTL) analysis of competitive ability for three weed species was conducted in the cross between cultivated and wild annual strains, and three QTLs for general competitive ability (GCA) were identified. GCA-QTLs conferred higher competitive ability by the cultivated rice alleles and were co-located with QTLs for plant architecture and root growth, detected in the same mapping population. Furthermore, a significant change in GCA was achieved by accumulation and epistatic interaction of three QTLs. Further studies on the genetic control of competitive ability would facilitate the breeding of competitive cultivars in rice.     

Strikingly different effects of cholesterol and 7-ketocholesterol on lipid bilayer-mediated aggregation of amyloid beta (1-42)

Oxidized cholesterol has been widely reported to contribute to the pathogenesis of Alzheimer's disease (AD). However, the mechanism by which they affect the disease is not fully understood. Herein, we aimed to investigate the effect of 7-ketocholesterol (7keto) on membrane-mediated aggregation of amyloid beta (Aβ-42), one of the critical pathogenic events in AD. We have shown that when cholesterol is present in lipid vesicles, kinetics of Aβ nuclei formation is moderately hindered while that of fibril growth was considerably accelerated. The partial substitution of cholesterol with 7keto slightly enhanced the formation of Aβ-42 nuclei and remarkably decreased fibril elongation, thus maintaining the peptide in protofibrillar aggregates, which are reportedly the most toxic species. These findings add in understanding of how cholesterol and its oxidation can affect Aβ-induced cytotoxicity.     

Isolation, Properties and a Possible Function of a Water-Soluble Chlorophyll a/b-Protein from Brussels Sprouts

A water-soluble Chl a/b-protein (CP673) was isolated and purifiedfrom Brussels sprouts (Brassica oleracea L. var. gemmifera DC).The protein had a molecular mass of 78 kDa and an isoelectricpoint of 4.7, consisted of three or four subunits of 22 kDaand was extremely heat-stable. Although CP673 contained aboutone Chl a per protein, the blue and red absorption bands ofChl a that consisted of three or four Chl a forms with differentabsorption maxima suggested that there are several differentmodes or sites of binding for Chl a. Chl a/b ratio of largerthan 10 also indicated that Chl b is present only in a smallfraction of CP673. The heterogeneity of CP673 in terms of compositionand binding of Chl suggests that Chl is not an intrinsic componentof the Chl-protein. Homology search showed that the N-terminalamino acid sequence of CP673 is highly homologous with thatof a 22 kDa protein that accumulates in water-stressed leavesof two Brassicaceae plants, rapeseed and radish, but not withthose of the light-harvesting Chl a/b-proteins of photosynthesis.A possible function of the water-soluble Chl-protein was discussed. (Received September 17, 1996; Accepted November 18, 1996)     

Photoconversion of a Water-Soluble Chlorophyll Protein from Chenopodium Album: Resonance Raman and Fourier Transform Infrared Study of Protein and Pigment Structures

A water-soluble Chl a/b-protein complex, CP668, from Chenopodiumalbum converts to another form of protein complex, CP743, uponlight illumination. Structural changes of pigments and proteinsupon photoconversion were studied using resonance Raman (RR)and Fourier transform infrared (FTIR) spectroscopies. RR spectraof CP668 and CP743 and a light-induced FTIR difference spectrumshowed that the macrocyle C=C bands of Chl a in CP668 considerablychanged upon conversion to the pigment (not chemically identifiedyet) in CP743. The C=C band pattern of the RR spectrum of CP743was similar to that of bacteriochlorophyll a, suggesting thatthe conjugated system of the CP743 pigment resembles a bacteriochlorinring. Judging from the C=O frequencies, the 13¹-keto C=O groupsof Chl a and b in CP668 are free from hydrogen bonding, whereasthe 13²-ester C=O groups of both Chl a and b and the 7-formylC=O of Chl b in CP668 are hydrogen bonded. Upon conversion toCP743, interactions of the 13¹-keto and 13²-ester C=O groupswere basically unaffected, demonstrating no drastic changesaround these C=O groups. FTIR spectra in the amide I' regionof CP668 and CP743 in D₂O buffer showed a peak at 1,633 cm^–1,which represents a major component of ß-sheet conformation.Second-derivative spectra of the amide I' bands as well as alight-induced FTIR difference spectrum suggested that drasticchange in the protein conformation does not occur upon photoconversion. (Received November 1, 1998; Accepted December 24, 1998)     

Inactivation or removal of the budded particles of a nuclear polyhedrosis virus of a silkworm, Bombyx mori L. (Lep., Bombycidae)

Effective methods to inactivate or remove budded particles of a nuclear polyhedrosis virus of Bombyx mori (BmNPV) from a cell-cultured media or from host haemolymph that is infected by this virus have been developed. Two types of suspensions containing BmNPV budded virus particles, TC-100 media that cultured BmN4 cells infected by this virus and haemolymph of B. mori larvae infected by this virus, were treated by 6% (w/v) polyethylene glycol (PEG), 0.01% (w/v) chitosan, 0.05% (v/v) linoleic acid (an emulsion), and/or diethylether. Treatment by linoleic acid followed by PEG-precipitation and treatment by diethylether followed by PEG-precipitation were so effective that these treatments suppressed the viral titre of BmNPV-infected larval haemolymph from an original titre (> 10⁹ TCID₅₀ units/ml) to below a detectable limit. These methods are suggested as being potentially useful in an insect factory system; that is, a protein production system utilizing a baculovirus vector and its insect host or cultured cells on a large scale.     

The hemodynamic effects of acute myocardial ischemia and reperfusion in Clawn miniature pigs.

Acute myocardial ischemia was induced by occluding the LAD in Clawn miniature pigs. Eight pigs (group 1) were subjected to 6 h ischemia and nine pigs (group 2) were subjected to 20 min ischemia, followed by reperfusion for 340 min. Three animals of the group 1 died due to ventricular fibrillation after occlusion and in group 2, four animals died due to the arrhythmia after reperfusion. Though the ischemic area of group 2 (15.6% of the ventricle) was narrower than that of group 1 (21.7%), the survival rate was lower. We supposed that ischemia-reperfusion injuries were strongly connected with the hemodynamics of group 2. Clawn miniature pigs are useful experimental animals for myocardial ischemic researches.     

Effects of pre- and pro-sequence of thaumatin on the secretion by Pichia pastoris

Thaumatin is a 22-kDa sweet-tasting protein containing eight disulfide bonds. When thaumatin is expressed in Pichia pastoris using the thaumatin cDNA fused with both the alpha-factor signal sequence and the Kex2 protease cleavage site from Saccharomyces cerevisiae, the N-terminal sequence of the secreted thaumatin molecule is not processed correctly. To examine the role of the thaumatin cDNA-encoded N-terminal pre-sequence and C-terminal pro-sequence on the processing of thaumatin and efficiency of thaumatin production in P. pastoris, four expression plasmids with different pre-sequence and pro-sequence were constructed and transformed into P. pastoris. The transformants containing pre-thaumatin gene that has the native plant signal, secreted thaumatin molecules in the medium. The N-terminal amino acid sequence of the secreted thaumatin molecule was processed correctly. The production yield of thaumatin was not affected by the C-terminal pro-sequence, and the pro-sequence was not processed in P. pastoris, indicating that pro-sequence is not necessary for thaumatin synthesis.     

Excitatory and inhibitory actions of norepinephrine on the Ba2+ current through L-type Ca2+ channels of smooth muscle cells of guinea-pig vas deferens

The effect of norepinephrine (NE) was examined on the whole-cell Ba²⁺ current through L-type Ca²⁺ channels of freshly isolated smooth muscle cells of guinea-pig vas deferens. The magnitude of maximum Ba²⁺ current [IBa(max)] varied in different cells, although the capacitance of the cell membrane was similar (∼50 pF). Application of dbcAMP augmented IBa(max) by 37%, which was canceled by Rp-cAMPs, while PMA decreased the current by 32%, which was canceled by staurosporine. NE increased IBa(max) of the cells which originally showed relatively small IBa(max), and decreased the current of the cells which showed larger IBa(max). In the presence of phentolamine, NE increased IBa(max), and this effect was remarkable in cells showed smaller IBa(max). In the presence of propranolol, NE decreased IBa(max). The excitatory β-adrenoceptor activation was canceled by Rp-cAMPs, and the inhibitory α-adrenoceptor effect was canceled by staurosporine. It is suggested that NE shows dual (excitatory and inhibitory) actions on the L-type Ca²⁺ channels of smooth muscle of guinea-pig vas deferens. The excitatory β-adrenoceptor action mediated through cAMP/PKA is predominant in cells with lower density of the Ca²⁺ channels, while inhibitory α-adrenoceptor action mediated through PKC is predominant in cells with higher channel density. © 1996 Wiley-Liss, Inc.     

Identification and characterization of integrin-binding sialoprotein (IBSP) genes in reptile and amphibian

Integrin-binding sialoprotein (IBSP) is a member of the small integrin-binding ligand N-linked glycoprotein (SIBLING) family; and the whole SIBLING family is further included in a larger secretory calcium-binding phosphoprotein (SCPP) family. SIBLING proteins are known to construct a part of the non-collagenous extracellular matrices of calcified tissues, and considered to have arisen by duplication and subsequent divergent evolution of a single ancient gene. To understand the alterations of SIBLING molecules associated with the evolution of calcified tissues in vertebrates, we initiated a search for lower vertebrate orthologs of SIBLING genes. In the present study, an IBSP ortholog from a reptile (caiman) and two distinct orthologs from an amphibian (African clawed toad) were identified and characterized. As expected, the toad IBSP genes were transcribed only in calcified tissue (jaw and tibia), as also seen in mammals. The caiman, toad, avian, and mammalian IBSPs share several unique features specific for IBSP and apparently have similar properties. Furthermore, analysis of the sequences suggested that the IBSP molecule might have gradually intensified its functions related to calcification during its evolutionary process through tetrapods.