Two genes that encode Ca2+-dependent protein kinases are induced by drought and high-salt stresses in Arabidopsis thaliana

Two cDNA clones, AATCDPK1 and cATCDPK2, encoding Ca²⁺-dependent, calmodulin-independent protein kinases (CDPK) were cloned from Arabidopsis thaliana and their nucleotide sequences were determined. Northern blot analysis indicated that the mRNAs corresponding to the ATCDPK1 and ATCDPK2 genes are rapidly induced by drought and high-salt stress but not by low-temperature stress or heat stress. Treatment of Arabidopsis plants with exogenous abscisic acid (ABA) had no effect on the induction of ATCDPK1 or ATCDPK2. These findings suggest that a change in the osmotic potential of the environment can serve as a trigger for the induction of ATCDPK1 and ATCDPK2. Putative proteins encoded by ATCDPK1 and ATCDPK2 which contain open reading frames of 1479 and 1488 bp, respectively, are designated ATCDPK1 and ATCDPK2 and show 52% identity at the amino acid sequence level. ATCDPK1 and ATCDPK2 exhibit significant similarity to a soybean CDPK (51 % and 73%, respectively). Both proteins contain a catalytic domain that is typical of serine/threonine protein kinases and a regulatory domain that is homologous to the Ca²⁺-binding sites of calmodulin. Genomic Southern blot analysis suggests the existence of a few additional genes that are related to ATCDPK1 and ATCDPK2 in the Arabidopsis genome. The ATCDPK2 protein expressed in Escherichia coli was found to phosphorylate casein and myelin basic protein preferentially, relative to a histone substrate, and required Ca²⁺ for activation.     

Influence of Potassium Concentration in Microdialysis Perfusate on Basal and Stimulated Striatal Dopamine Release: Effect of Ceruletide, a Cholecystokinin-Related Peptide

Abstract: The in vivo microdialysis method was used to study the effect of the cholecystokinin-related peptide, ceruletide, on extracellular levels of dopamine (DA) in the striatum following perfusion with various K⁺ concentrations. Increasing the K⁺ concentration in the perfusate from 4 to 15 or 17.5 m M did not change basal DA release or release evoked by electrical stimulation of the medial forebrain bundle (MFB). However, when the perfusing solution contained 20 or 30 m M K⁺, dose-dependent reductions of both basal and MFB-stimulated DA release occurred. Subcutaneous administration of ceruletide at 160 μg/kg had no influence on the basal or MFB-stimulated DA release with 4 or 15 m M K⁺ in the perfusate. However, after perfusion with 17.5 m M K⁺, ceruletide significantly attenuated the basal and MFB-stimulated DA release. Carbachol (10 μ M ) locally applied via the dialysis probe also attenuated MFB-stimulated DA release after perfusion with 17.5 m M K⁺. From these results, we conclude that under appropriate depolarization of striatal DA terminals, ceruletide induces further depolarization and inactivation of nigrostriatal DA terminals. The present data suggest that this effect may be mediated via intrinsic cholinergic neurons in the striatum.     

A model for feature linking via collective oscillations in the primary visual cortex

A neural network model for explaining experimentally observed neuronal responses in cat primary visual cortex is proposed. In our model, the basic functional unit is an orientation column which is represented by a large homogeneous population of neurons modeled as integrate-and-fire type excitable elements. The orientation column exhibits spontaneous collective oscillations in activity in response to suitable visual stimuli. Such oscillations are caused by mutual synchronization among the neurons within the column. Numerical simulation for various stimulus patterns shows that as a result of activity correlations between different columns, the amplitude and the phase of the oscillation in each column depend strongly on the global feature of the stimulus pattern. These results satisfactorily account for experimental observations.     

Cytotoxic cell function and phenotypic analysis of peripheral blood mononuclear cells in cancer patients treated with low-dose interleukin-2 and mitomycin C

We previously found that the ability of peripheral blood mononuclear cells (PBM) of cancer patients to generate lymphokine-activated killer (LAK) cells became remarkably augmented after mitomycin C administration. On the basis of the clinical finding, we designed a treatment regimen comprised of 12 mg/m² mitomycin C i. v. on day 1 and 700 U/m² recombinant interleukin-2 (IL-2) i.v. every 12 h from day 4 through day 8. Of 25 patients with advanced carcinoma, 9 had a partial response and 3 had a minor response. Cytotoxic cell function, including natural killer activity, lymphokine-activated killer (LAK) activity, and the ability to generate LAK cells, and lymphocyte subsets in PBM was measured 1 day before and after either the first or second course of this therapy. The relationship between these parameters and the clinical antitumor response to this treatment was examined. Although the cytotoxic activities were significantly augmented after either the first or second treatment course, no positive correlation was observed between the changes in these cytotoxic activities and the clinical response to this therapy, when patients who either showed a partial response or whose disease remission was partial or minor were defined as responders. Further, phenotypic analysis showed a significant increase in CD2⁺, CD3⁺ CD4⁺ and CD4⁺Leu8^– cells after the firs course, and CD25⁺ cells after either the first or second course of this treatment. The precentages of CD2⁺ and CD25⁺ cells were significantly elevated only in responders but not in nonresponders, suggesting the increase in these subsets was related to clinical response.     

Comparison of dispersal ability between the green leafhoppers,Nephotettix virescens andN. cincticeps (hemiptera: Cicadellidae) by tethered flight

Dispersal propensity of green leafhoppers was compared between a tropical species, Nephotettix virescens, and a temperate species, N. cincticeps. The flight ability was measured with tethered flight technique under laboratory conditions (25°C, 16L-8D). The pre-flight period was shorter and the flight duration was longer in N. virescens than in N. cincticeps in both sexes. No significant correlations were found between the flight activity and morphometric characters for either of the two species. The results suggested that dispersal propensity of N. virescens is higher than that of N. cincticeps.     

Tissue-Specific Isoforms of Catalase Subunits in Castor Bean Seedlings

Catalases purified from endosperm glyoxysomes and non-specializedmicrobodies from hypocotyls of castor bean seedlings differedin their specific activity [90–164 and 0.89–4.9kunits (mg protein)^–1, respectively] and in their constituentsubunits [two subunits of 54 and 56 kDa for the endosperm enzymeand only one of 56 kDa for the hypocotyl enzyme]. Immunoblotanalysis also showed that particulate fractions from the endospermsand from etiolated and green cotyledons contained two catalasesubunits of 54 and 56 kDa, whereas such fractions from the hypocotylsand roots contained only the 56-kDa subunit. Leaf peroxisomesfrom green leaves had two catalase subunits of around 55 kDaeach. Results of translation in vitro indicated that the 54-and 56-kDa subunits were translated from distinct mRNAs andlevels of both mRNAs increased in the endosperms during germination,prior to increases in levels of catalase proteins. In the hypocotyls,the 56-kDa subunit seemed to be synthesized constitutively. ¹Present addresses: YO, Toyota Central Institute, 31-9 Musashizuka,Nagabuchi, Nagakute, Aichi 480-11, Japan     

Suppression of Quantum Yield of Photosystem II by Hyperosmotic Stress in Chlamydomonas reinhardtii

Addition of ethylene glycol (EG) or NaCl to cells of Chlamydomonasreinhardtii induced transient non-photochemical quenching ofChl fluorescence correlated with the inhibition of photosyntheticoxygen evolution. The induction of the quenching and subsequentrecovery proceeded not only in the light but also in the dark.The quenching was almost unaffected by the protonophore nigericin,suggesting the involvement of a type of non-photochemical quenchingattributable to a state 2 transition. Higher concentrationsof EG or NaCl caused a delay of the recovery of the maximumfluorescence yield (Fm'). Dark reduction rate of P700⁺ afterthe application of a flash light in the presence of DCMU wasenhanced by the hyperosmotic shock, suggesting a stimulatedreduction of the intersystem electron carriers. It is proposedthat the osmotic stress stimulates electron donation from stromalcomponents via the NAD(P)H dehydrogenase, which results in thereduction of the intersystem chain and triggering of a state2 transition leading to stimulated cyclic PSI activity. (Received May 16, 1995; Accepted July 26, 1995)     

DIVERSITY OF HALOGENATED SECONDARY METABOLITES IN THE RED ALGA LAURENCIA NIPPONICA (RHODOMELACEAE,CERAMIALES)1,2

Many morphologically similar, but chemically distinct, populations have been found in the marine red alga Laurencia nipponica Yamada (Rhodomelaceae, Ceramiales) growing in Japan. Each chemical type is characterized by a specific end-product of halogenated secondaly metabolite synthesis: chamigrane-type sesquiterpenoids such as prepacifenol and halochamigrene epoxide and C₁₅ bromoethers such as laurencin, laureatin, isoprelaurefucin, epilaurallene, and kumausallene. These seven types of secondary metabolite syntheses remained the same in the wild and under various culture conditions. Because bromoethers and terpenoids are probably synthesized by different metabolic pathways, it is virtually certain that different sets of enzymes participate in their synthesis. Prepacifenol- and laureatin-producing populations were selected as representatives of terpenoid and bromoether groups, respectively. F₁ tetrasporophytes derived from crosses between reciprocal, female and male gametophytes of prepacifenol- and laureatin-producing strains bore both types of metabolites, suggesting that the genes Producing these enzyme systems are encoded by nuclear genomes. The F₁ gametophytes resulting from the reciprocal crosses produced either prepacifenol or laureatin, and the four individuals derived from spore tetrads (a set of tetraspores derived from a single tetrasporangium) produced either prepacifenol or laureatin in a 1:1 ratio, indicating that genes participating in terpenoid synthsis and those participating in bromoether synthesis are on different loci of homologous chromosomes and are segregated at meiosis (tetrasporogenesis). One individual of this interpopulational F₁ gamtophyte produced both parental types of metabolite, perhaps indicating the occurrence of a recombination type. Natural hybrid individuals, including such recombination-type gametophytes, were found in a sympatric locality at which these two chemical types occur. F₁ tetrasporophytes derived from crosses between respective prepacifenol- and laureatin-producing strains and their F₁ gametohytes produced only parental-type metabolite-producing plants. These results indicate that the diverse chemical types can be referred to as races (chemical races).     

Abscisic acid from Pinus densiflora pollen

(+)-Abscisic acid was isolated as the methyl ester from Pinus densiflora pollen and identified spectroscopically.