真菌发育过程中的蓝光诱导

本文对多种真菌在发育过程中受蓝光诱导的现象进行了综述。蓝光可以诱导多种真菌的形态发生和发育,包括孢子的产生和菌丝的延伸等。此外,蓝光还可引起真菌的生理和生化改变,如细胞膜对离子的通透性的变化、类胡萝卜素的合成等。真菌也存在一个蓝光信号系统,通过蓝光受体接受蓝光信号,导致了真菌的一系列形态发生和生理生化的变化。     

Influences of Blue and Red Light on the Photosynthetic Apparatus of Chlorella kessleri*

In white light of 33.2 μmol . m^?2 . s^?1 oxygen evolution of Chlorella kessleri is about 30 % higher after growth in blue light than after growth in red light of the same quantum fluence rate. When determined by the light-induced absorbance change at γ 820 nm, blue light-adapted cells possess about 60% more reaction centres per total chlorophyll in photosystem II. Correspondingly, the cells exhibit about 30% more Hill activity of PS II. Conversely, red light-adapted cells contain relatively more reaction centres and higher electron flow capacities of photosystem I. The distribution of total chlorophyll among the pigment-protein complexes, CPI, CPIa, CPa, and LHC II, corresponds to these data. There is more chlorophyll associated with the light-harvesting complex of PS II, LHC II, in cells under blue light conditions, but more chlorophyll bound to both complexes of PS I, CPI and CPIa, in cells under red light conditions. The respective ratios of chlorophyll a/chlorophyll b of all complexes are identical for blue and red light-adapted cells. This results in a higher relative amount of chlorophyll b in blue light-adapted cells. Total carotenoids per total chlorophyll are increased by 20% in red light-adapted cells. Their distribution among the pigment-protein complexes is unknown, however the ratios of lutein, neoxanthin and violaxanthin extractable from LHC II are different in blue (32.1:35.9:32.0) and in red (51.4:26.7:21.9) light-adaptod cells.     

Phototropism and Protein Phosphorylation in Higher Plants: Unilateral Blue Light Irradiation Generates a Directional Gradient of Protein Phosphorylation Across the Oat Coleoptile

Blue light induces the phosphorylation of a 116 kDa oat protein found in plasma membrane preparations from coleoptile tips. We developed a very sensitive in vitro method that allowed us to determine the tissue distribution of protein phosphorylation after applying unilateral and bilateral blue light pulses in vivo. We found that following unilateral in vivo irradiation the degree in phosphorylation of the 116 kDa protein is significantly higher at the irradiated than at the shaded side of the coleoptile tip. This asymmetry can be considered as previously missing criterion that protein phosphorylation represents an early event within the transduction chain for phototropism.     

Photoregulation of the Greening Process of Wheat Seedlings Grown in Red Light*

Wheat seedling grown with their shoot bottom exposed to red light (400 μmol m⁻² s⁻¹) either with constant illumination or light-dark cycles did not accumulate chlorophyll. This near-etiolation response was manifested by a critical threshold intensity of red light and did not need continuous illumination. The inhibition of the greening process resulted from reduced synthesis of glutamate-1-semialdehyde and consequent reduction in tetrapyrrole precursor 5-aminolevulinic acid. Red light perceived by the shoot bottom down regulated the protein and/or gene expression of enzymes involved in the biosynthesis of tetrapyrroles. The contents of endogenous cytokinins, i.e., isopentenyl-adenosine and dihydrozeatinriboside, were reduced in seedlings grown in red light having their shoot bottom exposed. Application of exogenous cytokinin and its analogue to roots of seedlings grown in red light reversed the down regulation of the greening process. The reversal of red-light-induced near-etiolation morphogenesis by far-red (200 μmol m⁻² s⁻¹) or blue (25 μmol m⁻² s⁻¹) light suggests that it could be a very high red-irradiance response of phytochrome, in the meristematic layers of the shoot bottom, that works in concert with blue light receptor(s). This work was supported by a competitive grant from the Department of Science and Technology, Govt. of India (DST/SP/SO/A-49/95) to BCT. Suchi Sood Varsha Gupta: Equal contributors     

蓝光对水稻幼苗生长及内源激素水平的影响

研究表明：与白光对照相比,蓝光明显抑制水稻幼苗的生长,并使幼苗体内的自由态IAA、GA1、玉米素和二氢玉米素含量下降,ABA含量和乙烯释放量则明显增加。说明蓝光对水稻幼苗生长的影响与其体内激素状况有关。     

Both phytochrome A and phytochrome B are required for the normal expression of phototropism in Arabidopsis thaliana seedlings

The role of phytochrome A (phyA) and phytochrome B (phyB) in phototropism was investigated by using the phytochrome-deficient mutants phyA-101 , phyB-1 and a phyA/phyB double mutant. The red-light-induced enhancement of phototropism, which is normally observed in wild-type seedlings, could not be detected in the phyA/phyB mutant at fluences of red light between 0.1 and 19 000 μmol m⁻². The loss of phyB has been shown to have no apparent effect on enhancement, while the loss of phyA resulted in a loss of enhancement only in the low fluence range (Janoudi et al. 1997). The conclusions of the aforementioned study can now be modified based on the current results which indicate that phototropic enhancement in the high fluence range is mediated by either phyA or phyB, and that other phytochromes have no role in enhancement. First positive phototropism was unaffected in phyA-101 and phyB-1 However, the magnitude of first positive phototropism in the phyA/phyB mutant was significantly lower than that of the wild-type Landsberg parent. Thus, the presence of either phyA or phyB is required for normal expression of first positive phototropism. The time threshold for second positive phototropism is unaltered in the phyA-101 and phyB mutants. However, the time threshold in the phyA/phyB mutant is about 2 h, approximately six times that of the wild type. Finally, the magnitude of second positive phototropism in both phyA-101 and phyB-1 is diminished in comparison with the wild-type response. Thus, phyA and phyB, acting independently or in combination, regulate the magnitude of phototropic curvature and the time threshold for second positive phototropism. We conclude that the presence of phyA and phyB is required, but not sufficient, for the expression of normal phototropism.     

Blue light-induced orientation movements of chloroplasts in higher plants: Recent progress in the study of their mechanisms

The discovery of phototropins, photoreceptors for chloroplast responses in Arabidopsis thaliana, brought about renewed interest in these blue light-controlled movements. Recent progress in research on their mechanisms in higher plants is briefly summarized. Phototropins mediate phototropism, chloroplast relocations and stomatal movements. Their functions are partially overlapping, with phot1 active predominantly in weak light and phot2 active in strong light. The accumulation response of chloroplasts appears to be mediated by phot1 and phot2 whereas the avoidance response is controlled by phot2. The role of Ca²⁺ as a potential intracellular messenger has been discussed in view of the recently demonstrated blue light-induced transient increases in the cytosolic Ca²⁺ mediated differently by phot1 and phot2. Differential inhibition of accumulation and avoidance responses by wortmannin, the inhibitor of phosphoinositide-3 kinases, in Lemna trisulca points to an important role of these enzymes in the signal transduction. A new, multi-domain component controlling chloroplast positioning and movement, CHUP1, encodes an actin-binding protein in Arabidopsis.     

Coaction of blue/ultraviolet-A light and light absorbed by phytochrome in controlling the appearance of ferredoxin-dependent glutamate synthase in the Scots pine (Pinus sylvestris L.) seedling

The appearance of NADH- and ferredoxin (Fd)-dependent glutamate synthases (GOGATs) was investigated in the major organs (roots, hypocotyl and cotyledonary whorl) of the Scots pine seedling. It was found that cytosolic NADH-GOGAT (EC 1.4.1.14) dropped to a low level during the experimental period (from 4 to 12 d after sowing) and was not significantly affected by light. On the other hand, plastidic Fd-GOGAT (EC 1.4.7.1) increased strongly in response to light. Whereas similar amounts of NADH-GOGAT were found in the different organs, Fd-GOGAT was mainly found in the cotyledons even in the presence of nitrate. Protein chromatography revealed only a single Fd-GOGAT peak. No isoforms were detected. Experiments to investigate regulation of the appearance of Fd-GOGAT in the cotyledonary whorl yielded the following results: (i) In darkness, neither nitrate (15 mM KNO₃) nor ammonium (15 mM NH₄Cl) had an effect on the appearance of Fd-GOGAT. In the light, nitrate stimulated Fd-GOGAT activity by 30% whereas ammonium had no effect. The major controlling factor is light. (ii) The action of long-term white light (100 W · m^–2) could be replaced quantitatively by blue light (B, 10 W · m^–2). Since the action of long-term far-red light was very weak, operation of the High Irradiance Reaction of phytochrome is excluded. On the other hand, light-pulse experiments with dark-grown seedlings showed the involvement of phytochrome. (iii) Red light, operating via phytochrome, could fully replace B, but only up to 10 d after sowing. Thereafter, there was an absolute requirement for B for a further increase in the enzyme level. It appears that the operation of phytochrome was replaced by the operation of cryptochrome (B/UV-A photoreceptor). (iv) However, dichromatic experiments (simultaneous treatment of the seedlings with two light beams to vary the level of the far-red-absorbing form of phytochrome (Pfr) in blue light) showed that B does not affect enzyme appearance if the Pfr level is low. It is concluded that B is required to maintain responsiveness of Fd-GOGAT synthesis to phytochrome (Pfr) beyond 10 d after sowing.Abbreviations and Symbols B blue light - c continuous - D darkness - Fd-GOGAT ferredoxin-dependent glutamate synthase (EC 1.4.7.1) - FR far-red light - HIR high-irradiance reaction of phytochrome - NADH-GOGAT nicotinamide-dinucleotide-dependent glutamate synthase (EC 1.4.1.14) - R red light - RG9 long-wavelength far-red light defined by the properties of the Schott glass filter (_RG9<0.01) - Pfr/Ptot far-red-absorbing form of phytochrome/total phytochrome, wavelength-dependent photoequilibrium of the phytochrome system Research supported by Deutsche Forschungsgemeinschaft (SFB 46 und Schwerpunkt Physiologie der Bäume). We thank E. Fernbach for his help with the dichromatic experiments.     

蓝光对水稻幼苗碳水化合物和蛋白质代谢的调节

分别以白光和黑暗处理为对照,蓝光处理１０ｄ的水稻幼苗碳水化合物含量下降,蛋白质含量增加,亚胺环已酮可抑制蓝光引起的蛋白质含量增加。蓝光处理的水稻幼苗总氨基酸含量比白光和黑暗处理分别提高１２％和３６％,游离态Ｇｌｕ、Ａｓｐ含量也比对照增加。蓝光处理促进水稻幼苗的呼吸作用,对丙酮酸激酶、硝酸还原酶、谷氨酰胺合成酶、谷氨酸合酶和转氨酶的活性表现出一致的促进效应。     

长波紫外线与8-甲氧基补骨脂素复合选育天蓝淡红链霉菌(S.coeruleorubidus) 高产株的研究

首次报道长波紫外线(near ultraviole)与8-甲氧基补骨脂素(8-methoxypsoralen)复合选育天蓝淡红链霉菌(S. coeruleorubidus)的研究结果,曾获柔红霉素较出发株稳增6.7%的高产株。