Effects of Gibberellin on Auxin-Induced Hyperpolarization of Cell Membranes in Hypocotyls of Vigna unguiculata

Auxin activates pumping of protons from the symplast to theapoplast and causes hyperpolarization of the symplast membranein the elongation zone of Vigna stems prior to the accelerationof growth. This auxin-induced hyperpolarization has been studiedin most cases in hypocotyl segments excised from the elongationzone. In the present study, mature-zone segments were perfusedwith IAA by the xylem perfusion technique in an effort to determinewhether or not IAA has any effects in the mature zone. Althoughno hyperpolarization of the symplast membrane was observed uponthe perfusion with auxin alone, auxin-induced hyperpolarizationwas observed when mature-zone segments had been pretreated withGA₃, in the absence of an increase in the growth rate. Theseresults suggest that cells in the mature zone have lost theability to activate the proton-pumping machinery in responseto auxin but that this ability can be restored by treatmentwith GA₃. This effect of GA₃ suggests the possibility that theconcentration of gibberellin in a tissue controls one of thecell's responses to auxin, namely, activation of the protonpump. (Received January 10, 1994; Accepted June 11, 1994)     

Phytochrome-mediated control of respiratory activities of mitochondria in cotyledons of dark-grown cucumber seedlings

Mitochondria isolated from cotyledons of dark-grown cucumber ( Cucumber sativus L., cv. Shimotsuki-Aonaga) seedlings after illumination with continuous far-red light showed an increased capacity for oxidation of malate or α-ketoglutarate, as compared with those from cotyledons of non-illuminated seedlings. This increase is supposed to be caused by phytochrome action (high irradiance response). Exogenous NAD⁺ had no effect on the rate of the oxidation of α-ketoglutarate or malate by mitochondria isolated from far-red light-treated cotyledons, but it enhanced the oxidation rate of mitochondria from control cotyledons to the level of mitochondria from light-treated ones. The NAD (NAD⁺+ NADH) content was higher in mitochondria isolated from continuously far-red light-treated cotyledons than in mitochondria from controls. The NAD content was also increased by the treatment with a red light pulse and this response was reversed by a subsequent far-red light pulse. It is proposed that phytochrome controls respiratory activities of cucumber mitochondria by changing the size of the NAD pool in the mitochondria.     

Localization of the vegetative cell wall hydrolases LytC, LytE, and LytF on the Bacillus subtilis cell surface and stability of these enzymes to cell wall-bound or extracellular proteases

LytF, LytE, and LytC are vegetative cell wall hydrolases in Bacillus subtilis. Immunofluorescence microscopy showed that an epitope-tagged LytF fusion protein (LytF-3xFLAG) in the wild-type background strain was localized at cell separation sites and one of the cell poles of rod-shaped cells during vegetative growth. However, in a mutant lacking both the cell surface protease WprA and the extracellular protease Epr, the fusion protein was observed at both cell poles in addition to cell separation sites. This suggests that LytF is potentially localized at cell separation sites and both cell poles during vegetative growth and that WprA and Epr are involved in LytF degradation. The localization pattern of LytE-3xFLAG was very similar to that of LytF-3xFLAG during vegetative growth. However, especially in the early vegetative growth phase, there was a remarkable difference between the shape of cells expressing LytE-3xFLAG and the shape of cells expressing LytF-3xFLAG. In the case of LytF-3xFLAG, it seemed that the signals in normal rod-shaped cells were stronger than those in long-chain cells. In contrast, the reverse was found in the case of LytE-3xFLAG. This difference may reflect the dependence on different sigma factors for gene expression. The results support and extend the previous finding that LytF and LytE are cell-separating enzymes. On the other hand, we observed that cells producing LytC-3xFLAG are uniformly coated with the fusion protein after the middle of the exponential growth phase, which supports the suggestion that LytC is a major autolysin that is not associated with cell separation.     

4-benzyl-3-phenyl-5H-furan-2-one, a vasodilator isolated from Malbranchea filamentosa IFM 41300

Screening of Malbranchea filamentosa IFM 41300 for bioactive compounds led to the identification of 4-benzyl-3-phenyl-5H-furan-2-one (1) as a vasodilator and erythroglaucin (2). The structure of 1 was established on the basis of spectroscopic and chemical investigations. Compound 1 inhibited Ca2+-induced vasocintraction in aortic rings pretreated with high K+ (60mM) or norepinephrine. Finally, compound 1 did not exhibit activity against human pathogenic microorganisms.     

Trap catches of the small brown planthopper, <Emphasis Type="Italic">Laodelphax striatellus</Emphasis> (Fallén) (Hemiptera: Delphacidae), in northern Kyushu district,Japan in relation to weather conditions

Abstract  

The pattern of overseas immigration of Laodelphax striatellus (Fallén) into northern Kyushu district in relation to weather conditions was analyzed using trap catch data, weather data, and backward trajectory analysis. The investigation covered the period May 21 to June 10 of each year between 2000 and 2009. One peak trap catch was recorded on May 27–28, 2006 and was associated with strong westerly winds at 850 and 925 hPa levels to the south of a cold vortex that passed over the southern part of the Korean peninsula. The backward trajectory analysis suggested Jiangsu Province, China, as possible migration source. Another peak catch on June 5, 2008 has already been reported as an overseas migration from Jiangsu Province, China. This study revealed that a cold vortex passing the southern Korean peninsula was also associated with insect migration in 2008. Thus, there is evidence of at least 2 overseas migrations from Jiangsu Province, China, over a 10-year period that coincided with strong westerly winds in the lower atmosphere that were associated with cold vortices.     

Annual fluctuations in the immigrant density of rice planthoppers, Sogatella furcifera and Nilaparvata lugens (Hemiptera: Delphacidae), in the Kyushu district of Japan, and associated meteorological conditions

We analyzed overseas immigrations of rice planthoppers in Kyushu, Japan, based on trap data collected during June?CJuly in 2000?C2011. The immigrant density was high in 2006, whereas it was low in 2008 and 2011. To understand these annual fluctuations, we investigated the relationships among trap catches and the following three meteorological conditions: (1) the average temperature during January?CFebruary in North Vietnam (T _NV), where planthoppers successfully overwinter; (2) the strong upper wind from North Vietnam to South China in April?CMay (UW_VC), when the first stage of migration occurs; (3) the strong upper wind from South China to Kyushu in June?CJuly (UW_CJ), when the second stage of migration occurs. In 2008 and 2011, T _NV values were 2.4?C3.0?°C below the 2000?C2011 average of 17.4?°C, and there were 9?C13 fewer days with a strong upper wind (UW_VC?+?UW_CJ) in April?CJuly compared with the 2000?C2011 average of 25?days. This study showed that the rice planthopper immigrant density during the last 12?years correlated significantly with T _NV and the number of days with a strong upper wind (UW_VC?+?UW_CJ) in April?CJuly. Thus, the meteorological conditions affected the immigrant density of rice planthoppers in Kyushu.     

Phosphorylation of Ser166 in RGS5 by protein kinase C causes loss of RGS function

RGS5 is a member of regulators of G protein signaling (RGS) proteins that attenuate heterotrimeric G protein signaling by functioning as GTPase-activating proteins (GAPs). We investigated phosphorylation of RGS5 and the resulting change of its function. In 293T cells, transiently expressed RGS5 was phosphorylated by endogenous protein kinases in the basal state. The phosphorylation was enhanced by phorbol 12-myristate 13-acetate (PMA) and endothelin-1 (ET-1), and suppressed by protein kinase C (PKC) inhibitors, H7, calphostin C and staurosporine. These results suggest involvement of PKC in phosphorylation of RGS5. In in vitro experiments, PKC phosphorylated recombinant RGS5 protein at serine residues. RGS5 protein phosphorylated by PKC showed much lower binding capacity for and GAP activity toward Galpha subunits than did the unphosphorylated RGS5. In cells expressing RGS5, the inhibitory effect of RGS5 on ET-1-induced Ca(2+) responses was enhanced by staurosporine. Mass spectrometric analysis of the phosphorylated RGS5 revealed that Ser166 was one of the predominant phosphorylation sites. Substitution of Ser166 by aspartic acid abolished the binding capacity to Galpha subunits and the GAP activity, and markedly reduced the inhibitory effect on ET-1-induced Ca(2+) responses. These results indicate that phosphorylation at Ser166 of RGS5 by PKC causes loss of the function of RGS5 in G protein signaling. Since this serine residue is conserved in RGS domains of many RGS proteins, the phosphorylation at Ser166 by PKC might act as a molecular switch and have functional significance.