Division‐site localization of RodZ is required for efficient Z ring formation in Escherichia coli

Bacteria such as Escherichia coli must coordinate cell elongation and cell division. Elongation is regulated by an elongasome complex containing MreB actin and the transmembrane protein RodZ, which regulates assembly of MreB, whereas division is regulated by a divisome complex containing FtsZ tubulin. These complexes were previously thought to function separately. However, MreB has been shown to directly interact with FtsZ to switch to cell division from cell elongation, indicating that these complexes collaborate to regulate both processes. Here, we investigated the role of RodZ in the regulation of cell division. RodZ localized to the division site in an FtsZ‐dependent manner. We also found that division‐site localization of MreB was dependent on RodZ. Formation of a Z ring was delayed by deletion of rodZ, suggesting that division‐site localization of RodZ facilitated the formation or stabilization of the Z ring during early cell division. Thus, RodZ functions to regulate MreB assembly during cell elongation and facilitates the formation of the Z ring during cell division in E. coli.     

Diversity and evolution of photosynthetic antenna systems in green plants

Photosynthetic antenna systems are mainly involved in the absorption of light energy required for photosynthesis. The typical green plants arrange chlorophylls a and b and carotenoids, including lutein and 9′‐cis neoxanthin, in their antenna systems; such antenna systems have prospered on earth. Therefore, these antenna systems should be highly evolved and should adapt to the photoenvironments in which plants grow. However, little information is available on the diversity and evolution of antenna systems in green plants as a whole. To approach this, the present study focused on the antenna systems in the Prasinophyceae, an assemblage of early diverging lineages of green plants and analyzed their photosynthetic pigments in detail. In the present study, various novel blue–green light‐absorbing siphonaxanthin series were detected in the early diverging species of the Prasinophyceae and the distribution of these carotenoids was revealed. Additionally, to clarify the evolution of antenna systems in the Ulvophyceae, a highly developed green algal group that specializes in inhabiting various aquatic environments, members of the Cladophorales belonging to this class were selected and their carotenoid compositions were determined to compare them with the molecular phylogenetic tree constructed on the basis of the 18S rRNA gene sequences of the Cladophorales. In this review, these data will be summarized and the remarkable variation of photosynthetic pigments will be presented. A possible scenario detailing the evolution of antenna systems in green plants will be elucidated.     

Effect of opioid agonist-antagonist interaction on morphine dependence in rats

Morphine dependence was induced by treatment with morphine-admixed food (0.25mg/g of food) for 7 days. Withdrawal was precipitated by injecting naloxone (0.5mg/kg, s.c.). Rats treated with morphine exhibited body weight loss upon the naloxone injection. When morphine-dependent rats were injected subcutaneously with morphine, codeine, meperidine and pentazocine 30 min before the naloxone injection, these drugs significantly suppressed the naloxone-precipitated loss of body weight in a dose-dependent manner. However, body weight loss induced through coadministration of naloxone and Mr-2266 BS were not suppressed by morphine pretreatment. These results suggest that opioids protect against naloxone-precipitated loss of body weight, and that mu and kappa opiate receptors play an important role in the protection against naloxone-precipitated withdrawal.     

Regulation of Auxin-induced Ethylene Biosynthesis. Repression of Inductive Formation of 1-Aminocyclopropane-1-carboxylate Synthase by Ethylene

Changes in the 1-aminocyclopropane-1-carboxylate (ACC) synthaseactivity which regulates auxin-induced ethylene production werestudied in etiolated mung bean hypocotyl segments. Increasesboth in ethylene production and ACC synthase activity in tissuetreated with IAA and BA were severely inhibited by cycloheximide(CHI), 2-(4-methyl-2,6-dinitroanilino)-N-methylpropionamide,actinomycin D and -amanitin. Aminoethoxyvinylglycine (AVG),a potent inhibitor of the ACC synthase reaction, increased theactivity of the enzyme in the tissue 3- to 4-fold. This stimulationalso was severely inhibited by the above inhibitors. Stimulationof the increase in the enzyme content by AVG was partially suppressedby an exogenous supply of ACC or ethylene. Suppression of theincrease in the enzyme took place with 0.3 µl/liter ethylene,and inhibition was increased to 10 µl/liter, which caused65% suppression. Air-flow incubation of the AVG-treated tissue,which greatly decreased the ethylene concentration surroundingthe tissue, further increased the amount of enzyme. Thus, oneeffect of AVG is to decrease the ethylene concentration insidethe tissue. The apparent half life of ACC synthase activity,measured by the administration of CHI, was estimated as about25 min. AVG lengthened the half life of the activity about 2-fold.Feedback repression by ethylene in the biosynthetic pathwayof auxin-induced ethylene is discussed in relation to the effectof AVG. (Received January 22, 1982; Accepted March 26, 1982)     

The role of proteoglycan synthesis in the development of sea urchins : II. The effect of administration of exogenous proteoglycan

The role of proteoglycan synthesis in the early development of sea urchins was studied by treating the embryos with a variety of inhibitors of proteoglycan synthesis and also with proteoglycan of exogenous origin. Developmental arrest at the blastula stage caused by p-nitrophenyl-β- -xyloside (p-NP-xyl) was cancelled by the administration of proteoglycan of exogenous origin. Proteoglycan of post-gastrular origin was effective for cancellation, but proteoglycan of blastular origin was not effective. This suggests that the hindrance of development by p-NP-xyl was due to the lack of proteoglycan synthesis at the late blastula stage. On the other hand, developmental arrest caused by 2-deoxy- -glucose (deoxy-glucose) and Na-selenate was not cancelled by the administration of proteoglycan under any condition tested. Apart from the cancelling action of proteoglycan, solely administered proteoglycan caused a blockage in development at a stage corresponding to the stage from which it was extracted, indicating that proteoglycan may be characterized by a kind of stage specificity.     

CAROTENOID COMPOSITIONS OF CLADOPHORA BALLS (AEGAGROPILA LINNAEI) AND SOME MEMBERS OF THE CLADOPHORALES (ULVOPHYCEAE,CHLOROPHYTA): THEIR TAXONOMIC AND EVOLUTIONARY IMPLICATION1

Photosynthetic pigments were analyzed by HPLC for 27 samples of the Cladophorales (Ulvophyceae, Chlorophyta). The carotenoid compositions of the examined algae were classified into three types based on the final compound of biosynthesis of the α‐carotene branch: lutein type, characterized by containing lutein as a major carotenoid and lacking loroxanthin and siphonaxanthin; loroxanthin type, characterized by containing loroxanthin and lacking siphonaxanthin; and siphonaxanthin type, characterized by containing siphonaxanthin. We constructed molecular phylogenetic tree of the species examined in the present study using 18S rRNA gene sequences and mapped the carotenoid types of the species onto the tree. The molecular phylogenetic analysis divided the Cladophorales into two major clades, clade 1 and Aegagropila‐clade (clade 2), and divided clade 1 into subclade 1‐1 and subclade 1‐2. All the examined species positioned in the Aegagropila‐clade and those of the subclade 1‐1 belonged to the loroxanthin type, whereas both lutein type and siphonaxanthin type appeared only in the subclade 1‐2. The clades delineated by molecular phylogenetic analysis were congruent with distribution of the carotenoid types, indicating that the carotenoid types are of taxonomic significance in the Cladophorales. Considering the distribution pattern of these carotenoid types and minimum state changes in the Cladophorales, we concluded that the loroxanthin type was the primitive (plesiomorphic) state and the siphonaxanthin type and lutein type appeared in the subclade 1‐2 as advanced (apomorphic) state within this order and suggested that the cladophoralean siphonaxanthin type would have been secondarily acquired.