Cloning and characterization of an allene oxide cyclase,PpAOC3, in <Emphasis Type="Italic">Physcomitrella patens</Emphasis>

Allene oxide cyclase (AOC) is a key enzyme in the octadecanoid pathway of flowering plants that synthesizes 12-oxo-phytodienoic acid (OPDA), which is a biosynthetic precursor of the signal molecule jasmonic acid (JA). A database search of the Physcomitrella patens genome revealed the presence of an AOC gene unique from the two previously reported AOC genes, PpAOC1 and PpAOC2. After cloning the identified AOC gene, designated PpAOC3, the obtained cDNA sequence (897 bp) was larger than the predicted AOC gene (765 bp) in the database because a speculated intron was not fully deleted. Although PpAOC3 did not display high similarity with AOC proteins from other species, recombinant PpAOC3 exhibited AOC activity and translocated to chloroplasts, as is observed for other AOC proteins. Notably, the expression profile of PpAOC3 differed from the other PpAOCs, as its expression in protonemata was higher than that in gametophores. Although the function of oxylipins such as OPDA and JA remains elusive in P. patens, further characterization of the enzymes in the octadecanoid pathway and the role of oxylipin will aid in the elucidation of physiological processes in this model bryophyte.     

On some basic laws in physiological systems

Summary By the application of a new concept of activity, which is an extension of excitability in physiology, it was possible to establish the activity cycle in relation to the interstimulus interval as an extension of excitability cycle. It was proved also that the response area and audiogram in the auditory system, as well as the spectral response curve in the visual system can be described in uniform fashion as a special situation of activity.It was further found that Fechner's law and Stevens' power function are none other than one of the laws of activity in the semi-logarithmic and in the double logarithmic domains, respectively.     

Replication origin of bacteriophage f1: Two signals required for its function

Plus strand synthesis in bacteriophage f1 initiates in a region of dyad symmetry at a specific site (plus origin) recognized and nicked by the viral gene II protein. In this paper we describe several small deletions on the 5′ side of the f1 plus origin which disrupt the region of dyad symmetry and extend up to only four nucleotides from the gene II protein nicking site. These deletions do not impair the ability of gene II protein in vitro to nick this site. However, they do inhibit in vivo plus strand synthesis. We conclude that the nucleotide sequence at the f1 plus origin contains at least two specific signals that are required for efficient plus strand synthesis.     

Vimentin Expression Pattern is Different between the Flank Region and Limb Regions of Somatopleural Mesoderm in the Chicken Embryo

It is known that the chicken flank somatopleure also has a limb-forming potential at early stages of development, but loses this potential later. Molecular changes during this process is, however, not well known. We obtained a monoclonal antibody which reacts to the flank somatopleure, but not to the wing bud, the leg bud and the neck somatopleure in the stage 22 chicken embryo. Further study revealed that this antibody is specific to vimentin. Time course of vimentin expression in the somatopleural mesoderm during the development was studied. It was revealed to be biphasic. Somatopleural mesoderm expressed vimentin at stage 10, but not at stage 16. Flank somatopleural mesoderm began to express vimentin again at stage 18, whereas limb bud mesenchymal cells did not until stage 27. The earlier re-expression of vimentin at the flank somatopleure suggests that certain physiological changes take place in cells at this region.     

Endogenous thiol protease inhibitor from rat liver

A thiol protease inhibitor was purified from rat liver by a rapid procedure involving heat treatment of the post-lysosomal fraction, affinity chromatography on papain-Sepharose 4B and Sephadex G-75. The purified inhibitor appeared homogeneous on sodium dodecyl sulfate electrophoresis. The inhibitor had a molecular weight of about 11,500 and consisted of three forms (pI 4.9, 5.2 and 5.6). The preparation inhibited thiol proteases, such as papain, cathepsin H, cathepsin B and cathepsin L, but not serine proteases (trypsin, chymotrypsin, mast cell protease and cathepsin A) or cathepsin D.     

Update on the possible mode of action of the jasmonates: Focus on the metabolism of cell wall polysaccharides in relation to growth and development

Jasmonic acid (JA) and its related compounds (jasmonates) applied to plant tissues exert either inhibitory or promotive effects in growth and developmental processes, which in some ways are similar to abscisic acid. However, little is known about the mode of action of the jamonates at the tissue or organ levels. Here, we review partial evidence for the physiological action of the jasmonates on cell elongation and abscission.
Jasmonates inhibit the IAA-induced cell elongation of oat coleoptile segments not by affecting energy production, osmoregulation and cell wall loosening, but by inhibiting the synthesis of cell wall polysaccharides. The inhibition is partially reversed by simultaneous application of sucrose. Inhibition of IAA-induced elongation by JA is only observed in monocotyledons, not in dicotyledons. These effects suggest that jasmonates exert their inhibitory effect on cell elongation by affecting the metabolism of the cell wall polysaccharides in monocotyledons.
Jasmonates promote the abscission of bean petiole explants without enhancing ethylene production. Cells in the petiole adjacent to the abscission zone expand during abscission. In the abscission zone, jasmonates decrease the amount of cellulosic but not that of noncellulosic polysaccharides. Jasmonates increase the activities of cellulase and decrease the levels of UDP-sugars, which are important intermediates for the synthesis of cell wall polysaccharides in the abscission zone, probably resulting in the decreased level of cellulose and the mechanical weakness of cell walls.
Thus, it is suggested that jasmonates exert their multiple physiological effects by affecting the metabolic processes of cell wall polysaccharides.