[Pathological changes in coal miner pneumoconiosis patients' larger airway mucosa]

OBJECTIVE

To study the pathological changes of the larger airway mucosa in coal miner pneumoconiosis patients.

METHOD

The 23 pneumoconiosis patients' specimens were observed under fibrobronchoscope and examined by optical microscope and transmission electron microscope, with 19 chronic bronchitis patients (all complicated with emphysema) and 5 workers who had the history of dust inhalation but no lesions in the lungs as the controls.

RESULTS

Scattered macular black areas, orifice stenoses and lumen abnormalities appeared in the larger airways of the pneumoconiosis patients and the controls who had the history of dust inhalation. Fibroplastic proliferation, smooth muscular distortion and lesions in various microstructures of columnar ciliated epithelial cells were also seen by microscopy among them.

CONCLUSION

The results showed that the above pathological changes were caused by the direct injuries of coal dust granules to the larger airways.

Low levels of erythroid and myeloid progenitors in thrombopoietin-and c-mpl-deficient mice

Thrombopoietin (TPO), the ligand for the c-mpl receptor, has been shown to be the major regulator of platelet production. Mice deficient in either c-mpl or TPO generated by homologous recombination show a dramatic decrease in platelet counts, but other blood cell counts are normal. Because TPO treatment of myelosuppressed mice not only enhances the recovery of platelets but also accelerates erythroid recovery, we investigated the levels of myeloid and erythroid progenitor cells in TPO-or c-mpl-deficient mice. Our results show that the number of megakaryocyte, granulocyte-macrophage, erythroid, and multilineage progenitors are significantly reduced in the bone marrow, spleen, and peripheral blood of either TPO-or c-mpl-deficient mice. Administration of recombinant murine TPO to TPO-deficient mice and control littermate mice significantly increased the absolute number of myeloid, erythroid, and mixed progenitors in bone marrow and spleen. This increase was especially apparent in TPO-deficient mice where numbers were increased to a level greater than in diluent-treated control mice and approached or equaled that in the TPO-treated control mice. Moreover, TPO-administration greatly increased the number of circulating progenitors as well as platelets in both TPO-deficient and control mice. Furthermore, the megakaryocytopoietic activity of other cytokines in the absence of a functional TPO or c-mpl gene was shown both in vitro and in vivo.

[The protective effects of dichloroacetate on cerebral ischemia after reperfusion of fed rats]

OBJECTIVE

To study the brain protective mechanisms of dichloroacetate (DCA) by observing the influence of DCA on the biochemical and pathological changes in ischemic brain tissues in different periods of reperfusion.

METHODS

The FED-RAT cerebral ischemic model induced by 4-vessel occlusion was applied. 55 mature male Sprague-Dawley rats were divided into the control group, normal saline and DCA-treated groups before ischemia, normal saline and DCA-treated groups after ischemia equally and randomly.

RESULTS

DCA could significantly lower the brain lactic acid, water content, and the diameter of cortical neurons, and protect the pathological damage of the membranaceous structure, before or after ischemia at a dose of 25 mg/kg, compared with the normal saline treated groups.

CONCLUSION

Lowering brain lactate, resisting brain edema and protecting the membranaceous structures are the main brain protective mechanisms of DCA in biochemistry and ultrastructure.

Relative reactivity of platelets from thrombopoietin- and interleukin-6-treated dogs

Previous reports have shown that interleukin-6 (IL-6) enhances the responsiveness of platelets to thrombin stimulation and has modest thrombocytopoietic effects in vivo. Thrombopoietin (TPO; mpl ligand) has been shown to have dramatic thrombocytopoietic effect in vivo, but little is known of its capacity to alter platelet function. In this study, a direct comparison of the effects of IL-6 and TPO on platelet function in dogs has been performed, with modest doses of TPO (1 microgram/kg/d) chosen to match or moderately exceed the platelet counts achieved with IL-6 (40 micrograms/kg/d) for 10 days. Platelet responsiveness to thrombin stimulation was assessed in TPO-treated, IL-6-treated, and control dogs by flow cytometric measurement of P-selectin expression. On day 5, the dose of thrombin promoting half maximal stimulation (EC50) of platelets was not significantly changed in TPO-treated dogs, whereas in IL-6-treated dogs the EC50 decreased to 73.1% +/- 6.1% (mean +/- 1 SD; n = 5) of control values (P < 0.01). These experiments were performed on both gel-filtered platelets and washed whole blood, indicating that the observed changes in EC50 were caused by cytokine-mediated alteration of platelets rather than plasma components. Because it has been shown that thiazole orange specifically labels a subpopulation of dog platelets that is less than 24 hours old, the thrombin responsiveness of these young, newly synthesized platelets was determined. The EC50 of thiazole orange-positive platelets from IL-6-treated dogs decreased dramatically by day 5 to 46.5% +/- 13.1% (n = 4) of control values (P < 0.001), whereas TPO-treated dogs did not significantly change. When TPO was directly incubated with platelets ex vivo, no effects on either thrombin-mediated P-selectin expression or adenosine diphosphate-induced fibrinogen binding were observed. These data show that IL-6 alters platelet function, as measured by reactivity to thrombin, whereas TPO does not. This divergence in function is observed even though TPO is equally, or more, effective at promoting platelet production under these experimental conditions.

[Changes of histamine receptors in the liver of the rat during the development of experimental cirrhosis]

It remains unknown whether changes of histamine H1 and H2 recepters in the liver occur during the development of cirrhosis. 48 male Wistar rats were divided, equally and randomly, into experiment and control groups, and the rats in the experiment group were induced by CCl4 to form experimental cirrhosis models. Then, at different stages during the development of experimental cirrhosis, the maximal binding capacity (Bmax), dissociation constants (Kd), and binding ability (BA = Bmax/Kd) of histamine H1 and H2 receptors in the livers of the two groups were analysed by radioligand binding assay. At early stage of the development of experimental cirrhosis, the Bmax of H2 receptor in the rat liver was not statistically different from that of normal control; at middle and advanced stages of the course, the Bmax of H2 recepter were significantly lower than normal. The Bmax of H1 receptor was obviously lower than normal at each stage. At middle stage, the Kd of H1 receptor was significantly higher than normal, whereas the Kd of H1 receptor at the other two stages and the Kd of H2 receptor at each stage were not remarkably different from those of the controls. At each stage of the development of experimental cirrhosis, the BA of H1 and H2 receptor was all significantly lower than that of the normal controls. It was concluded that the "down-regulation" of the receptors may be an important factor for the reduction of Bmax and BA of the two histamine receptors, and these changes of the receptors may possibly led to metabolic disorder of carbohydrates and phospholipid in the liver and lower the liver's ability to inactivate histamine.

[A sample survey and multiple factor analysis on asthma in urban area of Shanghai]

OBJECTIVE

To estimate the prevalence of asthma in urban residents of Shanghai in 1990 and evaluate the risk factors of asthma.

METHODS

A cluster uneven random survey of asthma was conducted among 36,872 urban residents, 5/1000 of the population of the city. The asthmatics were suspected based upon case history, and then confirmed by home visit and further investigation. Single factor and unconditional logistic regression analysis were employed to evaluate the risk factors of asthma.

RESULTS

The accumulative prevalence of asthma was 1.53% for age group 0-35 and it was higher in male (1.74%) than in female (1.31%). Sex, age and type of living house were possible risk factors. The prevalences were much higher among people with history of TB and pneumonia of which the values of relative risks were 2.53 and 4.95, respectively. Histories of food, drug and other kinds of hypersensitivity were significantly related to the history of asthma.

CONCLUSION

Several risk factors possibly associated with asthma were identified in Shanghai area.

An adaptive image segmentation method with visual nonlinearity characteristics

This correspondence is concerned with a method for image segmentation on the visual principle. The inconsistency between the conventional discriminating criterion and the human vision mechanism in perceiving an object and its background is analyzed and an improved discriminating criterion with visual nonlinearity is defined. A new model and an algorithm for image segmentation calculation are proposed based on the spatially adaptive principle of human vision and the relevant hypotheses about object recognition. This is a two-stage process of image segmentation. First, initial segmentation is realized with the bottom-up segmenting algorithm, followed by the goal-driven segmenting algorithm to improve the segmentation results concerning certain regions of interest. Experimental results show that, compared with some conventional and gradient-based segmenting methods, the new method has the excellent performance of extracting small objects from the images of natural scenes with a complicated background.

Multinuclear magnetic resonance studies of the interaction of inorganic cations with heparin

The interaction of Na+, Ca2+, Mg2+, Zn2+ and La3+ with heparin, a highly negatively charged glycosaminoglycan, was studied by 1H and 23Na nuclear magnetic resonance spectroscopy. 1H chemical shift and nuclear Overhauser effect (NOE) data indicate that the counter ions Na+, Ca2+ and Mg2+ interact with the low pH, carboxylic acid form of heparin by delocalized, long-range electrostatic interactions. At higher pH, 1H chemical shift and NOE data indicate that Na+ and Mg2+ continue to interact with heparin in the same manner, even upon deprotonation of the carboxylic acid group; however, there is a site-specific contribution to the binding of Ca2+, Zn2+ and La3+ under these conditions. Acid dissociation constants for heparin carboxylic acid groups and heparin-metal binding constants were determined from the pH dependence of 1H chemical shifts and 23Na spin-lattice (T1) relaxation times. Equilibrium constants for exchange of M2+ for heparin-bound Na+ were obtained from 23Na T1 data. The acid dissociation constants show a strong dependence on Na+ concentration due to the polyelectrolyte character of heparin.

Thrombocytopoietic properties of oncostatin M

Oncostatin M (OM) is a 28-kD glycoprotein that exhibits a panoply of biologic effects. Based on histologic observations of increased splenic megakaryocytes in nude mice implanted with an OM-secreting cell line, the thrombocytopoietic properties of OM in mice were investigated in culture and in vivo. Alone, OM did not induce megakaryocytic colony formation, but in combination with murine interleukin-3 (IL-3), OM markedly enhanced colony formation. The effects of OM on colony formation were similar to those of IL-6. OM alone augmented acetylcholinesterase in short-term marrow cultures. In normal mice, the administration of OM augmented platelet counts without increasing other circulating blood cell counts. The increment in counts exceeded that observed with IL-6. The kinetics of the OM response suggested that maximal increases in platelets occurred 3 days after the cessation of OM administration, irrespective of the duration of administration. In irradiated mice, OM administration accelerated platelet recovery and prevented the decrease in red blood cells observed in irradiated control animals. The data show that OM behaves as a megakaryocytic maturation factor in vitro and augments platelet production in vivo. Based on these animal data, OM may have potential clinical utility as a thrombocytopoietic agent.

The effect of the S14A mutation on the conformation and thermostability of Saccharomyces cerevisiae G-actin and its interaction with adenine nucleotides

The actin Ser14 hydroxyl is one of a number of ligands that binds to the gamma-phosphate of ATP thereby stabilizing the actin.ATP complex. In yeast actin, conversion of Ser14 to Ala (S14A), causes a temperature-sensitive phenotype in vivo and temperature-sensitive polymerization defects in vitro (Chen, X., and Rubenstein, P. A. (1995) J. Biol. Chem. 270, 11406-11414). Here, using a new luciferase-based procedure, we show that the mutation results in a 40-60-fold decrease in actin's affinity for ATP. The mutation causes a decrease in the intrinsic ATPase activity of both Ca- and Mg-G-actin at 30 degrees C and alters the protease susceptibility of sites on subdomain 2. Ca-S14A-actin but not Mg-S14A-actin binds etheno-ATP at 37 degrees C. Intrinsic tryptophan fluorescence measurements show that at 37 degrees C, Mg-S14A-actin but not the calcium form unfolds. CD measurements show the mutation causes a decrease in the apparent denaturation temperature for Ca-actin from 57 to 45 degrees C and for the magnesium form a decrease from 52 to 40 degrees C. Based on a re-examination of actin's crystal structure coordinates, we propose that the Ser14 hydroxyl forms a polar bridge between the ATP gamma-phosphate and the amide nitrogen of Gly74, thus conferring additional stability on the actin small domain.

Novel furostanol glycosides from Allium macrostemon

Further studies by means of preparative HPLC led to the isolation of two new furostanol saponins, macrostemonosides G (1) and I (3), along with an artifact, macrostemonoside H (2) from the bulbs of Allium macrostemon Bunge. On the basis of chemical evidence and spectral analyses (1H-,13C-NMR,1H-1H COSY,1H-13C COSY, HMBC and FAB-MS), the structure of 1 was established as 26-O-beta-D-glucopyranosyl-22-hydroxy-5 beta-furost-25(27)-ene-3 beta,12 beta,26 triol 3-O-beta-D-glucopyranosyl(1-->2)-beta-D-galactopyranoside and 2 as the 22-methoxy derivative of 1; 3 was deduced to be 26-O-beta-D-glucopyranosyl-22-hydroxy-5 beta-furost-25(27)-ene-12-one-3 beta,26- diol 3-O-beta-D-glucopyranosyl(1-->2)-beta-D-galactopyranoside. Preliminary pharmacological tests showed that macrostemonoside G (1) could inhibit ADP-induced human platelet aggregation in vitro (IC50 = 0.871 mM).

Isolation and preliminary characterization of gas1-1, a mutation causing partial suppression of the phenotype conferred by the gibberellin-insensitive (gai) mutation in Arabidopsis thaliana (L.) Heyhn

The semi-dominant gai mutation of arabidopsis confers a dark-green dwarf phenotype resembling that of gibberellin (GA)-deficient mutants. In contrast to GA-deficient mutants, gai mutants do not respond to GA treatments and accumulate higher levels of bioactive GAs than are found in wild-type controls. The gai mutation thus alters the responses of plant cells to GA, indicating that the GAI (wild-type) gene product is involved in GA reception and/or signal transduction. Here we describe the isolation and preliminary characterization of a mutation, gas1-1, which is not linked to gai and which partially suppresses the effect of the gai mutation. Double mutant, gai gas1-1, homozygotes are less severely dwarfed and lighter green than gai GAS1 controls. However, comparisons of the effects of treatments with exogenous GA demonstrate that gas1-1 does not increase the GA responsiveness of the gai mutant. Thus the gas1-1 mutation appears to reduce the GA-dependency of plant growth, and identifies a gene (GAS1) whose product is a candidate GA signal-transduction component.

Inheritance of gusA and neo genes in transgenic rice

Inheritance of foreign genes neo and gusA in rice (Oryza sativa L. cv. IR54 and Radon) has been investigated in three different primary (T0) transformants and their progeny plants. T0 plants were obtained by co-transforming protoplasts from two different rice suspension cultures with the neomycin phosphotransferase II gene [neo or aph (3') II] and the beta-glucuronidase gene (uidA or gusA) residing on separate chimeric plasmid constructs. The suspension cultures were derived from callus of immature embryos of indica variety IR54 and japonica variety Radon. One transgenic line of Radon (AR2) contained neo driven by the CaMV 35S promoter and gusA driven by the rice actin promoter. A second Radon line (R3) contained neo driven by the CaMV 35S promoter and gusA driven by a promoter of the rice tungro bacilliform virus. The third transgenic line, IR54-1, contained neo driven by the CaMV 35S promoter and gusA driven by the CaMV 35S. Inheritance of the transgenes in progeny of the transgenic rice was investigated by Southern blot analysis and enzyme assays. Southern blot analysis of genomic DNA showed that, regardless of copy numbers of the transgenes in the plant genome and the fact that the two transgenes resided on two different plasmids before transformation, the introduced gusA and neo genes were stably transmitted from one generation to another and co-inherited together in transgenic rice progeny plants derived from self-pollination. Analysis of GUS and NPT II activities in T1 to T2 plants provided evidence that inheritance of the gusA and neo genes was in a Mendelian fashion in one plant line (AR2), and in an irregular fashion in the two other plant lines (R3 and IR54-1). Homozygous progeny plants expressing the gusA and neo genes were obtained in the T2 generation of AR2, but the homozygous state was not found in the other two lines of transgenic rice.

[Retroviral-mediated transfer of human beta-globin gene and its enhancer into MEL cells]

The present result showed that human beta-globin gene has been integrated into amphotropic packaging cell line PA317 in 5/13 clones of PA317 beta and 1/14 clone of PA317 beta E0.4. Retrovirus titers of amphotropic recombinant retrovirus ranged from 10(3) to 10(4) CFU/ml. MEL cells were transfected by supernant of PA317 beta and PA317 beta E0.4. Northern blot showed that the expression of human beta-globin gene in MEL beta E0.4 was significantly higher than MEL beta in mRNA level. This result indicated that an enhancer which comes from HS II of human LCR can increase human beta-globin gene mRNA expression in transfected MEL. However, the retrovirus titers of PA317 beta and PA317 beta E0.4 in our experiment were low. When large fragment enhancer (0.4 kb) was inserted into retrovirus vector, it could bring about the human beta-globin gene deletion in amphotropic packing cells.

Further studies on new furostanol saponins from the bulbs of Allium macrostemon

Further studies by means of preparative HPLC led to the isolation of two new furostanol saponins, macrostemonoside J (1) and L (3), along with an artifact, macrostemonoside K (2) from the bulbs of Allium macrostemon. On the basis of chemical evidence and spectral analysis (1H-, 13C-NMR and FAB-MS), the structure of 1 was elucidated to be 26-O-beta-D-glucopyranosyl 2 beta,3 beta,22,26-tetrahydroxy-25(R)-5 beta-furostan 3-O-beta-D-glucopyranosyl (1-->2)-beta-D-galactopyranoside. 3 was deduced to be 26-O-beta-D-glucopyranosyl 2 beta,3 beta,26-trihydroxy-25(R)-5 beta-furostan- 20(22)-ene 3-O-beta-D-glucopyranosyl (1-->2)-beta-D-galactopyranoside.

Mammalian cell cultivation in space

In order to study the effect of microgravity on mammalian cell growth, proliferation and biosynthesis, the human T leukemia cells, human lung adenocarcinoma cells, EVI-H1 hybridoma cells and genetic engineering cells producing human growth hormone were flown on re-entry Scientific Satellite 90105 for a duration of eight days. The preliminary results indicate that the mammalian cells are sensitive to gravity. They might adapt to microgravity conditions leading to altered growth rate and subsequently, to altered biosynthesis and molecular secretion. In addition, their morphology may be affected in microgravity.

Alteration of platelet function in dogs mediated by interleukin-6

To determine if interleukin-6 (IL-6) administration influences platelet function, platelet activation was analyzed sequentially in IL-6-treated (80 micrograms/kg/d) and control dogs. Platelet activation was determined in whole blood by flow cytometry by quantitating the binding of a monoclonal antibody to platelet surface P-selectin after stimulation with graded doses of thrombin. Administration of IL-6 resulted in a twofold decrease in the thrombin concentration required for induction of half-maximal P-selectin expression (ED50) compared with control animals. The ED50 returned to normal after cessation of IL-6 administration. As measured by P-selectin expression, enhanced responsiveness to the strong agonist platelet activating factor (PAF) was also observed in the IL-6-treated dogs. IL-6 had no effect on the susceptibility of platelets to thrombin activation when incubated with anticoagulated dog blood. The data show that, in addition to augmenting the platelet count in normal dogs, IL-6 enhances the sensitivity of platelets to activation in response to thrombin and PAF.

Aged platelets have an impaired response to thrombin as quantitated by P-selectin expression

After the intravenous infusion of N-hydroxysuccinimido biotin into dogs, 80.6% +/- 9.7% (n = 5) of platelets were covalently labeled with biotin. The in vivo survival of the biotinylated platelets was monitored by flow cytometry and was normal as compared with previous reports for dog platelets. The ability of the biotinylated platelets to be activated was analyzed by measuring the expression of cell-surface P-selectin after incubation with graded concentrations of thrombin. When P-selectin expression was examined 3 hours after labeling, biotinylated platelets were indistinguishable from the nonlabeled population of platelets, indicating that biotinylation did not adversely affect the cells. On consecutive days after biotinylation, the thrombin dose-response curves for biotinylated and nonbiotinylated platelets were repeated, and as the biotinylated-platelets aged, they became less responsive to thrombin. On days 3, 4, and 5, the thrombin EC50 for the aged, biotinylated platelets as compared with the total population of platelets was 136%, 150%, and 178%, respectively. Increasing age clearly impairs the reactivity of platelets towards thrombin as quantitated by the expression of cell-surface P-selectin.

[Studies on the antitumor activity of organotin compounds]

Organotin compounds were found to obviously inhibit the activity of phospholipid/Ca(2+)-dependent protein kinase (PKC) in rat brain tissue and the proliferation of tumor cell lines in vitro. The results showed that a correlation exists between the effects on PKC and anti-proliferative and antitumor activities. The structure-activity relationship was shown to be as follows: (1) R, the organic group determines the biological activity; (2) electronegativity of the halogen can affect the activity. The organotin compounds inhibit tumor cells by its [SnR2]2+, and inhibit G1-->S phases of HL-60 cell cycle. The IC50 of [SnPh2F2], [SnPh2(CysOS)].H2O and [SnPh2Cl2.phen(CH3)2] are respectively 25, 15 and 20 mumol.L-1 on PKC, 0.5, 4.0 and 0.3 mumol.L-1 on HL-60 cells, 2.7, 9 and 1.5 mumol.L-1 on BEL-7402 cells, 2.2, 15 and 5.0 mumol.L-1 on KB cells. But no induction of differentiation of leukemic cell lines HL-60 and K562 was observed.

Nuclear magnetic resonance studies of the binding of captopril and penicillamine by serum albumin

The metabolism of the thiol-containing drugs penicillamine (beta,beta-dimethylcysteine) and captopril (D-3-mercapto-2-methylpropanoyl-L-proline) involves the formation of mixed disulfides, including mixed disulfides with serum albumin. The reactions of penicillamine and captopril with serum albumin in aqueous solution and in intact human blood plasma have been studied by 500 MHz 1H NMR spectroscopy. Penicillamine was found to react rapidly at the albumin-cysteine mixed disulfide bond to form penicillamine-cysteine mixed disulfide and to react more slowly at other albumin disulfide bonds. The amino acid cysteine was found to react with albumin by the same two pathways. In contrast, captopril rapidly associates with albumin to form noncovalent albumin-captopril complexes. Exchange of captopril between its free and noncovalently bound forms takes place on the NMR time scale. On a longer time scale, captopril reacts with albumin by thiol/disulfide interchange reactions. Noncovalently bound captopril displaced lactate from its albumin binding sites, both in aqueous solution and in human plasma. The results demonstrate that 1H NMR is a useful method for characterizing the state of drug molecules in human plasma and for detecting and monitoring perturbations by drugs of delicately balanced binding equilibria involving endogenous small molecules and macromolecules in plasma.

[Study on the relationship between two second-messenger pathways on the regulation of proliferation and differentiation in MGc 80-3 cells]

By using an inducer of differentiation (HMBA) and blockers of signal pathways, the relationship between two second-messenger pathways (DG-PKC, cAMP-PKA) in inducer-mediated MGc80-3 cell differentiation was studied. Cells were treated with HMBA for 24 h, levels of DG decreased by 64.7%, activity of PKC decreased by 28.7%, while levels of cAMP and rate of it's protein binding increased by 62% and 32.6% respectively (after treated for 48 h, the result was more remarkable). PKA-R II distributed in nuclei. H7 (PKC inhibitor) was used to substitute for HMBA to block the DG-PKC pathway. After treatment for 24 h, the levels of DG and activity of PCK both decreased, while the levels of cAMP increased 1.04 times. On the contrary, PKA inhibitor was added while HMBA was used to induce cell differentiation, cAMP-PKA pathway was blocked, levels of cAMP and rate of it's protein binding decreased. But levels of DG and activity of PKC both increased to the levels of control cells. At this time, PKA-R II distributed only in cytoplasm. These results suggest that harmonious relations of the positive and negative regulation of cAMP-PKA and DG-PKC systems in cells during the proliferation and differentiation of cells. It also showed that positive regulation of PI system may play a leading role in MGc80-3 cells. It let to normal regulation of two signal pathway out of control to remain malignant phenotype of these cells.

On the structure of calonyctin A, a plant growth regulator

The plant growth regulator calonyctin A, isolated from the dried leaves of Calonyction aculeatum L. House (Yue-Guang-Hua), was separated into two pure components by high performance liquid chromatography. By use of mass spectrometry based on various ionization techniques, one- and two-dimensional NMR spectroscopy, IR spectrometry, and chemical methods the molecular structures of the two homologous glycosides were determined. Each molecule contains two hydroxy fatty acid residues and four 6-deoxyhexose units. The fatty acids are 3-hydroxy-2-methylbutanoic acid and 11-hydroxytetradecanoic acid or 11-hydroxyhexadecanoic acid. The 6-deoxyhexose residues (three of quinovose and one of rhamnose) comprise a tetrasaccharide having the following structure: [formula: see text] The long-chain hydroxy acid is linked glycosidically through its O-11 to Qui D and esterified to O-2 of Qui C, forming a macrocyclic lactone. The 3-hydroxy-2-methylbutanoic acid is ester-linked to O-3 of Qui C.

Phytochrome A null mutants of Arabidopsis display a wild-type phenotype in white light

Phytochrome is a family of photoreceptors that regulates plant photomorphogenesis; the best-characterized member of this family is phytochrome A. Here, we report the identification of novel mutations at three Arabidopsis loci (fhy1, fhy2, and fhy3) that confer an elongated hypocotyl in far-red but not in white light. fhy2 mutants are phytochrome A deficient, have reduced or undetectable levels of PHYA transcripts, and contain structural alterations within the PHYA gene. When grown in white light, fhy2 mutants are morphologically indistinguishable from wild-type plants. Thus, phytochrome A appears to be dispensable in white light-grown Arabidopsis plants. fhy2 alleles confer partially dominant phenotypes in far-red light, suggesting that the relative abundance of phytochrome A can affect the extent of the far-red-mediated hypocotyl growth inhibition response. Plants homozygous for the recessive fhy1 and fhy3 mutations have normal levels of functional phytochrome A. The FHY1 and FHY3 gene products may be responsible for the transduction of the far-red light signal from phytochrome A to downstream processes involved in hypocotyl growth regulation.