不同育秧方式和插植密度下晚籼稻群体动态结构的研究

不同育秧方式和插植密度下晚籼稻群体动态结构存在差异。旱育秧群体分蘖速度快,分蘖能力强。稀植可促进个体分蘖多发、有效穗数增多,但旱育稀植并无分蘖早发的优势。旱育稀植使主茎基部叶片变短而上部叶片变长,生育后期叶面积消长平稳,地上部干物质积累较多。旱育秧、稀植都使主茎叶总数增多,全生育期延长。     

Polymerization of Actin from Maize Pollen

Here we describe the in vitro polymerization of actin from maize (Zea mays) pollen. The purified actin from maize pollen reported in our previous paper (X. Liu, L.F. Yen [1992] Plant Physiol 99: 1151-1155) is biologically active. In the presence of ATP, KCl, and MgCl2 the purified pollen actin polymerized into filaments. During polymerization the spectra of absorbance at 232 nm increased gradually. Polymerization of pollen actin was evidently accompanied by an increase in viscosity of the pollen actin solution. Also, the specific viscosity of pollen F-actin increased in a concentration-dependent manner. The ultraviolet difference spectrum of pollen actin is very similar to that of rabbit muscle actin. The activity of myosin ATPase from rabbit muscle was activated 7-fold by the polymerized pollen actin (F-actin). The actin filaments were visualized under the electron microscope as doubly wound strands of 7 nm diameter. If cytochalasin B was added before staining, no actin filaments were observed. When actin filaments were treated with rabbit heavy meromyosin, the actin filaments were decorated with an arrowhead structure. These results imply that there is much similarity between pollen and muscle actin.     

An unusual Group 2 LEA gene family in citrus responsive to low temperature

Six cDNAs representing unique cold-induced sequences have been cloned from the hardy citrus relative Poncirus trifoliata. Among these, pBCORc115 and pBCORc119 were found to belong to the same gene family. Sequencing data indicated that pBCORc115 and pBCORc119 each contained an open reading frame, coding for a 19.8 kDa protein (COR19) and a smaller 11.4 kDa protein (COR11) respectively. Inspection of the deduced amino acid sequences revealed three large repeats in COR19, but only one was present in the COR11. Two elements: a Q-clustered tract and a K-rich motif were identified in each repeat. The K-rich motifs were similar to those of cotton D-11 and Group 2 LEA proteins. A Serine-cluster, a common feature in many Group 2 LEA-like proteins, was also found in these proteins, but it was in an unusual position at the carboxy-terminus. A bipartite motif of basic residues, similar to known nuclear targeting sequences, was also present in COR19 and COR11, suggesting that members of this protein family may have a nuclear targeting function. The expression of COR19 mRNA in response to cold acclimation, drought, flooding, and salinization was examined. COR19 expression in leaf tissue was induced in response to cold acclimation, but repressed during drought and flooding stress.     

The serum response factor nuclear localization signal: general implications for cyclic AMP-dependent protein kinase activity in control of nuclear translocation.

We have identified a basic sequence in the N-terminal region of the 67-kDa serum response factor (p67SRF or SRF) responsible for its nuclear localization. A peptide containing this nuclear localization signal (NLS) translocates rabbit immunoglobulin G (IgG) into the nucleus as efficiently as a peptide encoding the simian virus 40 NLS. This effect is abolished by substituting any two of the four basic residues in this NLS. Overexpression of a modified form of SRF in which these basic residues have been mutated confirms the absolute requirement for this sequence, and not the other basic amino acid sequences adjacent to it, in the nuclear localization of SRF. Since this NLS is in close proximity to potential phosphorylation sites for the cAMP-dependent protein kinase (A-kinase), we further investigated if A-kinase plays a role in the nuclear location of SRF. The nuclear transport of SRF proteins requires basal A-kinase activity, since inhibition of A-kinase by using either the specific inhibitory peptide PKIm or type II regulatory subunits (RII) completely prevents the nuclear localization of plasmid-expressed tagged SRF or an SRF-NLS-IgG conjugate. Direct phosphorylation of SRF by A-kinase can be discounted in this effect, since mutation of the putative phosphorylation sites in either the NLS peptide or the encoded full-length SRF protein had no effect on nuclear transport of the mutants. Finally, in support of an implication of A-kinase-dependent phosphorylation in a more general mechanism affecting nuclear import, we show that the nuclear transport of a simian virus 40-NLS-conjugated IgG or purified cyclin A protein is also blocked by inhibition of A-kinase, even though neither contains any potential sites for phosphorylation by A-kinase or can be phosphorylated by A-kinase in vitro.     

Transmitter-Induced Calcium Responses Differ in Astrocytes Acutely Isolated from Rat Brain and in Culture

Abstract: Glial fibrillary acid protein (GFAP)-positive astrocytes isolated from the cerebral cortices of 3–10-day-old rats frequently showed increased intracellular Ca²⁺ concentration responses to l -glutamate and glutamate analogues. However, few of the acutely isolated cells responded to ATP, and no such cells responded to serotonin [5-hydroxytryptamine (5-HT)]. The same cell that failed to respond to ATP or 5-HT often responded to glutamate. Culturing acutely isolated cells in media containing horse serum decreased Ca²⁺ responses to glutamate but increased the responses to ATP and induced responses to 5-HT. In primary cultures prepared from the cerebral cortices of 1-day-old rats and cultured in horse serum, fewer of the cells responded to glutamate, but almost all cells responded to ATP and 5-HT. The lack of, or limited response to, 5-HT or ATP in the acutely isolated cells seems unlikely to be due to selective damage to the respective receptors because acutely isolated GFAP-negative cells showed responses to ATP, several different proteases and mechanical dissociation yielded cells that also responded to glutamate but not to ATP, and exposure of primary cultures to papain did not abolish Ca²⁺ responses to several transmitters. The responses of the acutely isolated cells to glutamate but limited or lack of responses to ATP and 5-HT also correspond to what has been seen so far for astrocytes in situ. Thus, the present studies provide direct evidence that some of the receptors seen in primary astrocyte cultures may reflect a response to culture conditions and that, in the context of the relevant information so far available, acutely isolated astrocytes seem to reflect better the in vivo state.     

Studying dynamic process of photosensitization by ESR method

By kinetic methods, functional relation of TAN radical, produced in the process of TEMPONE trapping O2, vs. time during photosensitization was established. Accordingly relative rate constants of generating all kinds of active intermediates through types I and II mechanism of photosensitization can be calculated. Using the formula and experimental results, the relative rate constants of generating O2, O2 and PS2 of three kinds of perylenequinone photosensitizer: HA, HB and CP in DMF-H20 and DMSO-H2O system were calculated, and then the structure-activity relationship of perylenequinone photosensitizer and the relation between photosensitivity and solvent was studied.     

为害枣树一菱纹叶蝉新种

为害枣树一菱纹叶蝉新种蔡平（安徽农学院园艺系合肥２３００３６）崔士英（河北师范大学生物系石家庄０５００１６）葛钟麟（安徽农学院植保系合肥２３００３６）菱纹叶蝉属（Ｈｉｓｈｉ。。ｏｎｕｓＩｓｈｉｈａｒａ。１９５３）隶属于同翅目（ＨｏｍｏＰｔｅｒａ）ｎ十...     

内皮素－1对缺氧肺动脉平滑肌细胞的增殖作用

内皮素（ＥＴ）是至今所发现的最强的内源性血管收缩肽,近年来发现ＥＴ－１能促进血管平滑肌细胞增殖。本研究表明ＥＴ－１对缺氧培养的肺动脉平滑肌细胞（ＰＡＳＭＣ）有剂量依赖的增殖作用,缺氧可促进ＰＡＳＭＣ的ＤＮＡ合成且增加ＥＴ－１的丝裂原作用。ＥＴ－１的丝裂原作用主要由其Ａ型受体（ＥＴＲ＿Ａ）所介导,ＥＴＲ＿Ａ的特异拮抗剂ＢＱ１２３可显著抑制缺氧以及缺氧与ＥＴ－１协同所产生的增殖作用,而且发现ＥＴＲ＿Ａ在缺氧培养的ＰＡＳＭＣ中的表达显著高于常氧对照组ＰＡＳＭＣ。本研究表明ＥＴ－１参与了缺氧性肺动脉结构重组,而缺氧可增强ＰＡＳＭＣ对ＥＴ－１的增殖反应性。