摘要:

AbstractCellular adhesion is what keeps cells together in multicellular organisms. Cells adhere to each other, to extracellular matrices, and to the substratum. Biochemical analyses of these processes have suggested some of the types of surface molecules which may be involved, but definitive evidence must rely on effective reconstruction of functional membranes or genetic alteration of the pertinent genes. Together these approaches may give us a better understanding of how cells sort out and form tissues during development.

ISSN:0192-253X    

DOI:10.1002/dvg.1020040202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractMutants were selected that are incapable of differentiating microcysts, a resting stage formed in response to high osmotic conditions. In the selection procedure amebae that failed to encyst were removed by flotation in 46% Percoll. Genetic crosses among 15 mutant strains were made by means of the macrocyst sexual cycle. Eleven of the strains mapped to three loci. Mutations at two of these loci (cysA andcysB) produced no observable alteration in the aggregation‐fruiting pathway, although one set of strains altered at thecysA locus carried defects at a second unlinked site which blocked aggregation. The single strain that defined the third locus (cysC) is aggregateless. These results confirm the conclusion that there are several genes whose function is essential to microcyst development and is exclusive to this pathway. It remains uncertain whether there are other genes whose action is crucial to both encystment and to aggregation/fruitin

ISSN:0192-253X    

DOI:10.1002/dvg.1020040203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractMutations in 13 genes with temperature‐sensitive (ts), flightless phenotypes have been examined. All hop and fly well when raised at the permissive temperature, but fly poorly, or not at all, when raised at the restrictive temperature. The mutations were divided into three groups on the basis of their temperature‐sensitive periods (TSPs) for flightlessness. The TSPs for mutations at five loci,fli‐C1, D1, E1, I1, andshak A1, in the first group are confined to 24 to 48 hr interval during early pupal development. Mutations in the second group, includingeag101,fli B1, andfuts1have continuous TSPs 3 to 4 days in length, extending from late larval through the early pupal stages. The flight TSPs for mutations in the third class, includingfli J1,fli K2,flrd H3, andflrd N1, are almost continuous, and span most of the larval and pupal periods. Many of the mutations have pleiotropic phenotypes, including semilethality and lethality, and wing posture and cuticle abnormalities, with discernible TSPs. One of the more intriguing pleiotropic phenotypes is the ts optomotor response exhibited byfli J2, the TSP for which extends from late larval through late pupal s

ISSN:0192-253X    

DOI:10.1002/dvg.1020040204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThe timing of gene expression in the endosperm of developing F1maize kernels was investigated. Zymogram analysis revealed the presence of maternally derived allelic gene products on all days investigated, but activity of paternally derived allelic gene products is not detectable until days 6–8 postpollination, depending on the particular cross used and the enzyme investigated. This pattern holds true for eight different isozymes of five different enzyme systems, including catalase, alcohol dehydrogenase, glutamate‐oxaloacetate transaminase, endopeptid́ase, and aminopeptidase. An increase in specific activity for catalase, alcohol dehydrogenase, and endopeptidase correlates precisely with the day of visualization of the paternally derived allelic gene product on the zymograms. Rocket immunoelectrophoresis confirms a dramatic increase in catalase and alcohol dehydrogenase protein levels on the day the paternally derived allelic gene product is first detected on zymograms. Appropriate crosses utilizing three different allelic variants revealed the presence of enzyme of maternal plant origin within the endosperm prior to day 6 postpollination.Maize kernels were cultured in vitro on an agar‐based medium as early as 3 days postpollination. Using medium supplemented with actinomycin D or cycloheximide, it was possible to localize the critical time periods for transcription and translation of the paternally derived allele in the F1hybrids. For aminopeptidase (AMP‐1, AMP‐3) and endopeptidase (ENP‐1), transcription occurs as early as 3–4 days postpollination, and translation of the transcripts starts at about 4–5 days postpollination. Although the evidence is indirect, it is likely that the maternally derived allele of the F1kernels is activated (ie, begins transcribing) synchronously with the paternally derived allele during this early developme

ISSN:0192-253X    

DOI:10.1002/dvg.1020040205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThe effect of food supply on the onset of asexual and sexual plasmodium formation in Physarum polycephalum was studied. Asexual differentiation occurs readily in amoebae carrying thematAh mating type allele. The density at which these amoebae begin to differentiate is influenced by theindlocus, which controls the production of a diffusible inducer. The allelesind‐1andind‐2are known. Strains carring theind‐1allele begin plasmodium formation at a low amoebal density (rapid differentiation), while strains carring theind‐2allele differentiate at a higher amoebal density (slow differentiation). The onset of differentiation is characteristic of the strain and did not change with a 20‐fold variation in the number of food bacteria available. Sexual differentiation occurs between compatible amoebal strains. For a given pair of amoebal strains the onset of plasmodium formation occurs at a characteristic cell density that is determined by the genetic backgrounds of the strains. Theindlocus is one of the genes that influences this cell density. Plasmodia are formed at a lower cell density in crosses involving compatible amoebae carrying theind‐1allele than they are in crosses with strains carrying theind‐2allele. As was found for asexual differentiation, an approximate 20‐fold variation in the food supply did not affect the initiation of sexual plasmodium formation. These results suggest that in most cases starvation does not trigger the differentiation of amoebae into plasmodia. The time of onset of plasmodium formation is determined largely by

ISSN:0192-253X    

DOI:10.1002/dvg.1020040206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractCultured leaf tissues of Nicotiana tabacum L. cv. “Havana 425” normally require an exogenous source of cytokinin for rapid growth; stem‐cortex tissues do not—ie, they exhibit the cytokinin‐habituated phenotype. We found that plants regenerated from cloned cortex and leaf tissues from one particular plant differed in leaf‐tissue phenotype: Leaf tissues derived from leaf cells exhibited the normal, nonhabituated phenotype, whereas leaf tissues derived from cortex cells were cytokinin‐habituated. This difference in leaf phenotype was not found using leaf and cortex cells from six other donor plants. The inheritance of the habituated leaf trait was studied in tissues from cortex‐derived plants and hybrids between these plants and normal plants. F1hybrids were intermediate between the parental types in degree of habituation. No differences were found between reciprocal hybrids. These results suggest that the habituated leaf trait is an incompletely dominant, nuclear trait. Both parental and intermediate phenotypes were recovered in the F2progeny. The frequency of habituated leaf progeny in the F2and backcross populations provide evidence that the trait is regulated at a singl

ISSN:0192-253X    

DOI:10.1002/dvg.1020040207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

ISSN:0192-253X    

DOI:10.1002/dvg.1020040208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

ISSN:0192-253X    

DOI:10.1002/dvg.1020040201

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY