Differences between Spinach and Kidney Bean Plants in Terms of Sensitivity to Fumigation with NO2

Fumigation of plants of five species with NO₂ in darkness causedvisible injuries to leaves, with the most severe injuries inkidney bean plants and the least severe in spinach plants. Fumigationof these plants in the light caused virtually no visible injuries.NO₂-fumigated leaves accumulated nitrite in the darkness butnot in the light. The level of accumulated NO₂^– was decreasedby light much more rapidly in spinach leaves than in those ofkidney bean, with much less injury to spinach leaves than tothose of kidney bean. A larger amount of NO₂^– accumulatedin the trifoliate leaves of kidney bean plants cultivated withNO₃^– as a main source of nitrogen than in those of plantscultivated with NH₄⁺, and the former plants were more susceptibleto injury from NO₂ than the latter. Administration of NO₂^–to leaves of spinach and kidney bean plants induced the destructionof Chi in the light. The extent of the destruction of Chi wassmaller in spinach than in kidney bean, consistent with theirrespective responses to NO₂. The NO₂^–-induced destructionof Chi was inhibited to some extent by scavengers of free radicals.Activities of superoxide dismutase (SOD) were higher in leavesof spinach than in those of kidney bean. These results indicatethat NO₂^– is the toxic species generated by fumigationwith NO₂ and that spinach has a greater tolerance for NO₂ thankidney bean, probably as a result both of a higher capacityfor reduction of NO₂^– and a higher level of activity ofSOD. (Received June 5, 1991; Accepted January 27, 1992)     

Accumulation of Species-Specific Amino Acid Replacements That Cause Loss of Particular Protein Functions in Buchnera, an Endocellular Bacterial Symbiont

Endosymbiotic bacteria live in animal cells and are transmitted vertically at the time of the host's reproduction. In view of their small and asexual populations with infrequent chances of recombination, these endocellular bacteria are expected to accumulate mildly deleterious mutations. Previous studies showed that the DNA sequences of these bacteria evolved faster than those of free-living bacteria. In this study, we compared all the ORFs of Buchnera, an endocellular bacterial symbiont of aphids, with those of 34 other prokaryotic organisms and estimated the effect of the accelerated evolution of Buchnera on the functions of its proteins. It was revealed that Buchnera proteins contain many mutations at the sites where sequences are conserved in their orthologues in many other organisms. In addition, amino acid replacements at the conserved sites are mostly changes to physicochemically different amino acids. These results suggest that functions and conformations of Buchnera proteins have been seriously impaired or strongly modified. Indeed, extensive loss of functional motifs was observed in some Buchnera proteins. In many Buchnera proteins mutations were not detected evenly throughout each molecule but tended to accumulate in some functional units, possibly leading to loss of specific functions. As Buchnera has an unusual and limited gene repertory, it is conceivable that the manner of interactions among its proteins has been changed, and thus, functional constraints over their amino acid residues have also been changed during evolution. This may account for the loss of some functional units only in the Buchnera proteins. We obtained evidence that amino acid replacements in Buchnera were not always deleterious, but neutral or, in some cases, even positively selected. Received: 14 December 2000 / Accepted: 12 March 2001     

The crystal and molecular structure of 1-methyl-3-carbamoyl-pyridinium:indole-3-acetic acid (1:1) monohydrate complex. A model for the intermolecular stacking interaction between the indole ring and NAD+.

The crystal and molecular structure of the title complex has been determined by X-ray diffraction methods. The crystals contain one water molecule per asymmetric unit, which plays a important role in the molecular packing by forming hydrogen bonds with two carboxyl oxygen atoms of indole-3-acetic acid and a carbamoyl nitrogen atom of the 1-methyl-3-carbamoylpyridinium cation. Prominent stacking between the indole ring and the pyridinium ring, caused by the π_D?π_A interaction, is observed. This overlap with substantial result may provide a model for the stacking interaction between NAD⁺ and the tryptophanyl residues in the proteins.     

Cloning and characterization of ribosomal RNA gene of Physarum polycephalum

As a first step in studies on the structure and expression of rRNA gene of Physarum polycephalum, the cloning of the gene in Escherichia coli with plasmid vector DNAs was performed and 8 different kinds of clones containing 26S, 19S, and 5.85 rRNA genes were obtained. Using these cloned fragments, the location of these rRNA genes was determined by the Southern hybridization and S1 mapping method. Cloning of rDNA fragments made it possible to analyze the fine structure of the rDNA.     

Developmentally-regulated expression of mNapor encoding an apoptosis-induced ELAV-type RNA binding protein.

Proteins with RNA recognition motifs (RRMs) participate in many aspects of RNA metabolism, and some of them are required for the accomplishment of normal development. The neuroblastoma apoptosis-related RNA binding protein (NAPOR) is an ELAV-type RNA-binding protein with three characteristic RNP2/RNP1-type RRMs, which we identified as a gene induced during apoptosis of neuroblastoma cells. Here we isolated and characterized the cDNA for mNapor, the mouse homolog of NAPOR. The mNapor encodes mRNA sharing striking homology with that of NAPOR, not only in its open reading frame (98.5%) but also in the 3'-untranslated region (80.1%), and is mapped to chromosome 2 A2-A3, a region syntenic to the human NAPOR locus. In situ hybridization analysis revealed that the expression pattern of mNapor is spatially and temporally coincident with the occurrence of programmed cell death, suggesting its involvement in the development of the central nervous system in which apoptosis plays a crucial role.