A method for determining the position and size of optimal sequence regions for phylogenetic analysis

The availability of fast and accurate sequencing procedures along with the use of PCR has led to a proliferation of studies of variability at the molecular level in populations. Nevertheless, it is often impractical to examine long genomic stretches and a large number of individuals at the same time. In order to optimize this kind of study, we suggest a heuristic procedure for detection of the shortest region whose informational content can be considered sufficient for significant phylogenetic reconstruction. The method is based on the comparison of the pairwise genetic distances obtained from a set of sequences of reference to those obtained for different windows of variable size and position by means of a simple index. We also present an approach for testing whether the informative content in the stretches selected in this way is significantly different from the corresponding content shown by the larger genomic regions used as reference. Application of this test to the analysis of the VP1 protein gene of foot-and-mouth-disease type C virus allowed us to define optimal stretches whose informative content is not significantly different from that displayed by the complete VP1 sequence. We showed that the predictions made for type C sequences are valid for type O sequences, indicating that the results of the procedure are consistent. Correspondence to: J. Dopazo     

鸡爪草属的染色体及其系统位置

本文研究了毛茛科鸡爪草Calathodes oxycarpa的核形态。其静止核和有丝分裂前期染色体分别属于复杂中央染色微粒型和中间型,中期染色体属于R型,核型公式为2n=16=8sm 8st(2sat)。据此并结合有关资料,讨论了鸡爪草属与毛茛科其它类群的亲缘关系,认为鸡爪草属与金莲花属和特产于南朝鲜的Megaleranthis属是极为近缘的类群,不宜将它们分开置于不同的族或亚科中。     

Silent T-DNA genes in plant lines transformed by Agrobacterium tumefaciens are activated by grafting and by 5-azacytidine treatment

Summary A shooty tumor induced by a shooter mutant of an octopine strain of Agrobacterium tumefaciens was cloned. One clone obtained (TS038) behaved aberrantly in that it grew as a shooty tumor tissue on phytohormone free medium, but did not contain octopine synthase activity. In line TS038 the genes for octopine synthase and for the enzymes involved in agropine and mannopine synthesis were present, but were not transcribed. However, the above genes became active in TS038 tumor shoots after grafting as well as after treatment with the hypomethylating agent 5-azacytidine. After an unusually long incubation period in the growth cabinet shoot cultures appeared to have developed small shoots from the top of the leaves. This unusual form of differentiation was found to be accompanied by the induction of octopine synthase activity.     

The systematic relationships ofAegialitis (Plumbaginaceae) as revealed by pollen morphology

Light and first SEM observations on the pollen ofAegialitis indicate that the two species of the genus are clearly distinguishable from all other genera of the tribeStaticeae to whichAegialitis presently is relegated. Intraspecific exine or aperture dimorphism which appears frequently in this tribe, is not recorded in this genus.A. annulata andA. rotundifolia have distinct monomorphic pollen and show a great resemblance in exine features with the tribePlumbagineae, particularly species ofPlumbago. Considering these and other features, separate subtribal status forAegialitis within thePlumbagineae is proposed.     

Light-dependent conformational change at rhodopsin's cytoplasmic surface detected by increased susceptibility to proteolysis

Rhodopsin in bovine photoreceptor disk membranes was subjected to limited proteolysis by thermolysin, removing twelve amino acids from rhodopsin's carboxyl terminus. (1) The rate of proteolysis is significantly faster with rhodopsin following exposure to light than with unbleached rhodopsin, provided that the incubation conditions (pH, temperature) favor the formation of metarhodopsin II. (2) If the disk membranes are illuminated under conditions in which metarhodopsin I is the predominant photoproduct (pH 8.5, 0°C), no increase in the rate of proteolysis is observed compared to unilluminated membranes. (3) The light-induced increase in the rate of proteolysis is transient: it slowly decays in the dark to the original rate found for unbleached rhodopsin. The enhanced susceptibility to proteolysis appears to measure a conformational change at rhodopsin's cytoplasmic surface which is first exhibited at the metarhodopsin II stage. This and possibly other light-dependent changes may allow rhodopsin to mediate its signal as a light-receptor protein by binding to and activating certain rod cell enzymes.     

The changes of nuclear position and distribution of circumferentially aligned cortical microtubules during the progression of cell cycle inAdiantum protonemata

The intracellular positions of the nucleus and of cortical, circumferentially aligned microtubules (CCAM) in filamentous, single-celled protonemata ofAdiantum capillus-veneris were determined throughout the cell cycle in the dark. When apical growth continued at G₁ phase, the nucleus migrated keeping a constant distance from the tip. When the apical growth stopped at late S or G₂ phase, the nucleus stopped moving forward and then slightly moved backward to the site of cytokinesis. The CCAM were found only in the dome of protonemal tip when growing under continuous red light; they increased in number after dark incubation for 12 hr and then decreased after 20th hr in the dark. The CCAM were usually observed in the region between the nucleus and the tip at 28 hr in the dark. They were located around the nuclear region at pre-prophase and prophase, but then totally disappeared at metaphase and thereafter.     

Plant tumor reversal associated with the loss of foreign DNA

Summary Transformation of plant tissues into crown gall tumors has been associated with the transfer of a portion of a tumor-inducing plasmid (Ti-plasmid) into plant DNA. Various laboratories have regenerated normal-appearing plants from a number of crown gall tumors. This study investigates the fate of the foreign DNA in a series of tissues derived from various parts of a plant regenerated from the tumor BT-37 by Braun and his coworkers. It was found that all the foreign DNA sequences were lost from tissues that had lost all their tumorous traits; whereas the plasmid DNA sequences were still present in tissues that appeared normal but still exhibited tumorous traits when returned to tissue culture media. From these studies it would appear that the presence of the Ti-plasmid sequences in the plant DNA is required for the maintenance of the transformed state. Presented in the Symposium on Gene Transfer, Differentiation and Neoplasia in Plant and Animal Cells at the 30th Annual Meeting of the Tissue Culture Association, Seattle, Washington, June 10–14, 1979. This symposium was supported in part by Grant CA 26748 from the National Cancer Institute, DHEW, and Grant RD-67 from the American Cancer Society.     

Temperature-sensitive loss of tumor characteristics in a tobacco crown gall strain

Summary Three independently isolated tobacco crown gall strains incited byAgrobacterium tumefaciens C58 required phytohormone (auxin and cytokinin) supplements in the basal medium to grow, at 37°C. Six other tobacco crown gall strains incited, respectively, byA. tumefaciens IIBV7, B6, CGIC, A6NC, 27 and AT4 expressed, at 37°C, the tumor characteristic of ability to grow in vitro on medium lacking phytohormones. Nopaline was not detectable in C58 tumors cultured at 37°C, but octopine was produced by B6 tumor tissues incibated at the elevated temperature. C58 tumor strains kept at 37°C for 1 week or more lost the ability to express tumor characteristics at 27°C such as tissue morphology, growth on basal medium lacking phytohormones and nopaline production. Heat-treated C58 tissues also differed from the original tumor strain in regeneration ability and phytohormone requirements of explants; i.e. explants from regenerated, heart-treated C58 tumors required both auxin and cytokinin for growth in vitro.     

Body size clines in the European badger and the abundant centre hypothesis

Aim To test the abundant centre hypothesis by analysing the physical and climatic factors that influence body size variation in the European badger (Meles meles). Location Data were compiled from 35 locations across Europe. Methods We used body mass, body length and condylo‐basal length (CBL) as surrogates of size. We also compiled data on latitude, several climatic variables, habitat type and site position relative to the range edge. We collapsed all continuous climatic variables into independent vectors using principal components analysis (PCA), and used a general linear model to explain the morphometric variation in badger populations across the species’ range. Results Body mass and body length were nonlinearly and significantly related to latitude. In contrast, CBL was linearly related to latitude. Body mass changed nonlinearly along the temperature (PC1) gradient, with the highest values observed at mid‐range. Furthermore, body mass, body length and CBL differed significantly among habitats, with badgers showing larger size in temperate habitats and core areas relative to peripheral zones. Main conclusions Our analysis supports the nonlinear pattern predicted by the abundant centre hypothesis only for body mass and body length. These results imply that individuals are largest and heaviest at the centre of the climatic range of badger distribution. Variation of CBL with latitude follows a linear trend, consistent with Bergmann’s rule. Our results provide mixed support for the abundant centre hypothesis, and suggest food availability/quality to be the main mechanism underlying body size clines in this species.