Changes in the Number and Size of Chloroplasts during Senescence of Primary Leaves of Wheat Grown under Different Conditions

Changes in the number and size of chloroplasts in mesophyllcells were investigated in primary leaves of wheat from fullexpansion to yellowing under different growth conditions. Thenumber of chloroplasts per cell decreased slowly, although thedecrease was steady and statistically significant, until thelast stage of leaf senescence, when rapid degradation of chloroplaststook place. Rates of leaf senescence, or the decline in thenumber of chloroplasts, varied greatly among plants grown atdifferent seasons of the year, but about 20% of chloroplastsalways disappeared during the phase when steady loss of chloroplastsoccurred. The area of chloroplast disks also decreased graduallybut significantly, with a rapid decrease late in senescence.Thus, the total quantity of chloroplasts per mesophyll celldecreased substantially during leaf senescence. Yellowed leavescontained numerous structures that resemble oil drops but nochloroplasts. Decreases in rates of photosynthesis that occurduring senescence may, therefore, be largely due to decreasesin the quantity of chloroplasts. However, a better correlationwas found between the decrease in the maximum capacity for photosynthesisand the degradation of RuBP carboxylase. When plants had beengrown with a sufficient supply of nutrients, the number of chloroplastsdecreased steadily but at a reduced rate and the reduction inthe area of chloroplast disks was strongly suppressed. Thus,the quantitative decrease in chloroplasts in senescing leavesappears to be regulated by the requirements for nutrients (nitrogen)of other part of the plant. ³Present address: Department of Biology, Faculty of Science,Toho University, Miyama, Funabashi, Chiba, 274 Japan     

Difference in the responses of male cicada Meimuna opalifera to the two parts of conspecific calling song

Meimuna opalifera males emit extremely complex calling songs, with the main section comprising two parts. To investigate whether these two parts of the calling song have different meanings for the receivers, we conducted playback experiments. We counted and compared the number of response calls when different types of sound stimuli were presented under laboratory conditions. Meimuna opalifera males emitted significantly greater response calls during the playback of stimuli containing the former part of the songs than those containing the latter part only. This suggests that M. opalifera males tend to respond by detecting characteristics in the former part of the songs. Because the peak frequencies were similar between the former and the latter parts, the temporal patterns of the songs might be important in short-range communication between males of M. opalifera.     

Effect of overexpression of kinase- or RNase-deficient OsIRE1 on the endoplasmic reticulum stress response in transgenic rice plants

IRE1 is an endoplasmic reticulum (ER) stress sensor protein in eukaryotes. In this study, we generated transgenic rice plants overexpressing three types of OsIRE1, including wild-type OsIRE1 (IRE1-OE) and two disrupted-IRE1s deficient in either kinase activity (K519A-OE) or RNase activity (K833A-OE), under the control of a constitutive promoter. Overexpression of wild-type IRE1 induced the ER stress response in transgenic rice even under non-stress conditions, whereas K519A-OE and K833A-OE had dominant negative effects on endogenous OsIRE1 expression in these transgenic plants. These lines exhibited phenotypes that were quite similar to those of OsIRE1 knock-down rice. These observations suggest that the two types of functionally disrupted OsIRE1 proteins behave as competitive inhibitors toward the ER stress response in transgenic rice plants. Furthermore, OsIRE1 may have a vital, as yet unidentified function, as determined through the characterization of the transgenic plants generated in this study.     

A newly established human acute lymphoblastic leukemia cell line with characteristics of the earliest B-cell maturation

A new human acute lymphoblastic leukemia (ALL) cell line, designated HBL-3, was established from the bone marrow of a patient with non-T-ALL. The HBL-3 cell line expressed B4 (CD 19), BA-1 (CD 24) and HLA-DR antigens, but not surface immunoglobulin (SIg) or cytoplasmic immunoglobulin (CIg). The cell line lacked the common acute lymphoblastic leukemia antigen (CALLA) and antigenic markers characteristic of T-cell and myeloid cell lineages. The HBL-3 cells had structural rearrangements of both the homologous chromosome 9s, including a translocation with chromosome 1 which has been reported in a patient with common ALL. The cell line had rearranged immunoglobulin heavy chain genes but retained germ-line kappa light chain genes and germ-line T-cell receptor beta- and gamma-chain genes. The HBL-3 cell line was strongly positive for terminal deoxynucleotidyl transferase (TdT). These findings indicate that the HBL-3 cell line is derived from the earliest B-cell committed to B-cell lineage.     

Non-Ewald methods: theory and applications to molecular systems

Several non-Ewald methods for calculating electrostatic interactions have recently been developed, such as the Wolf method, the reaction field method, the pre-averaging method, and the zero-dipole summation method, for molecular dynamics simulations of various physical systems, including biomolecular systems. We review the theories of these approaches and their potential applications to molecular simulations, and discuss their relationships.     

Sequence characterized amplified region markers tightly linked to the mating factors of Lentinula edodes.

Detecting the mating types in shiitake, Lentinula edodes (Berk.) Pegler, is important for making progress in the breeding of this mushroom and determining the compatibility of the pair to cross. Shiitake is a tetrapolar fungus with two unlinking mating factors, A factor and B factor. We screened molecular markers linked to the mating factors using the randomly amplified polymorphic DNA (RAPD) method to develop the mating type identification procedure. Using 147 oligonucleotide primers, a total of 6 linkage markers for the shiitake mating factors, 4 markers for the A factor and 2 markers for the B factor, were discovered with a logarithm of the odds threshold of 3.0 for linkage. Two RAPDs that perfectly segregated with each mating factor among 72 basidiospore strains were detected. Both of these RAPDs were cloned and sequenced to convert them to the sequence characterized amplified region (SCAR) markers. Four primers, two sets of primers, were designed according to the internal sequences of two RAPDs tightly linking to the A factor or B factor. Consequently, we determined the polymerase chain reaction condition for multiplex analyses of these SCAR markers.     

Changes in Protein Content and in the Structure and Number of Chloroplasts during Leaf Senescence in Rice Seedlings

Two types of experiment were carried out to examine whetheror not the inactivation of photosynthesis is related to lossof chloroplasts during foliar senescence of rice seedlings.Levels of both soluble and insoluble leaf proteins decreasedduring senescence, the loss of the soluble proteins being fasterthan that of the insoluble ones. There was a good positive correlationbetween the rate of oxygen evolution and the level of solubleproteins. The inactivation of photosynthesis was also linearlyrelated to the loss of a major fraction of insoluble proteins.Thus, the loss of photosynthetic ability is ascribable to thedegradation of relevant proteins and enzymes during leaf senescence.Electron microscopy revealed that senescence caused the disorientationof the grana and stroma thylakoids, a decrease in the numberof starch granules, and an increase in the size and number ofplastoglobuli. Large grana consisting 20 to 30 thylakoids appearedin aged leaves. In addition to these changes in ultrastructure,there was a significant decrease in the size of chloroplasts.Furthermore, the number of chloroplasts in mesophyll cells wasalso notably reduced during senescence. Thus, the loss of leafproteins and inactivation of photosynthesis are both relatedto the decrease in the total mass of chloroplasts during senescenceof rice seedlings. ³Present address: Department of Botany, Faculty of Science,University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113 Japan. (Received January 4, 1989; Accepted April 19, 1989)     

Electron-opaque annular structure girdling the constricting isthmus of the dividing chloroplasts ofHeterosigma akashiwo (Raphidophyceae, Chromophyta)

Summary The plastokinesis (kinesis of chloroplasts) of a raphidophyte alga,Heterosigma akashiwo, was studied by electron microscopy using rapid freezing and freeze-substitution techniques. The chloroplasts are enveloped by two pairs of tightly appressed double membranes, the inner and the cytoplasmic outer pair. The inner pair constricts to divide in advance of the outer pair. By observation of serial sections an electron-opaque, annular structure (plastid-dividing ring) was observed at the isthmus of constricting chloroplasts, girdling the periplastidal outer surface of the inner pair of the four surrounding membranes. These observations suggest that the mechanisms underlying the constriction of the inner and outer pair may differ from each other. The localization of the annular structure (plastid-dividing ring) suggests that the inner pair of the surrounding membranes may be homologous to the double envelope membranes of the chloroplasts of Chlorophyta and Rhodophyta. In addition these findings provide a new evidence supporting the secondary endosymbiosis hypothesis for the origin of the chloroplasts in chromophyte algae.