Structure, function, and motility of vacuoles in filamentous fungi

Current information on the structure and function of motile tubular vacuoles in Pisolithus tinctorius and other fungi is reviewed. The use of fluorochromes to label the vacuole lumen is evaluated and observations on the structure and motility of vacuoles in P. tinctorius are differentiated from possible artifacts. The styryl dyes FM4-64 and MDY-64, used in yeast to demonstrate endocytosis, show little or no labeling of internal membranes in undamaged P. tinctorius cells. This agrees with our data showing that other probes for endocytosis such as Lucifer yellow CH are not taken up by hyphal tip cells. Overall, the observations do not support endocytosis in hyphal tips. It has been suggested that tubular vacuole systems carry out longitudinal transport, and evidence in favor of this hypothesis is evaluated. New data are presented to show that many of the large vacuoles in subapical cells are attached to the plasma membrane and are relatively immobile, while video sequences show movement of fluorochrome in pulses along a series of several large vacuoles, all interconnected via tubules. Tubular vacuoles from thick sections of hyphae processed under anhydrous conditions are shown by X-ray microanalysis to contain relatively high levels of P and K, as seen previously in the larger vacuoles. These results provide further evidence for a role of the tubular vacuoles in longitudinal transport of P. Copyright 1998 Academic Press.     

STAT1 is involved in signal transduction in the EPO induced HEL cells

Erythropoietin(EPO) is the major regulator of mamalian erythropoisis,which stimulates the growth and differentiation of hematopoietic cells through interaction with its receptor(EPO-R),Here we use HEL cells (a human erythro-leukemia cell line) as a model to elucidate the pathway of signal transduction in the EPO-induced HEL cells.Our data show that the EPOR (EPO receptor) on the surface of HEL cells interacts with the Janus tyrosine protein kinase(Jak2) to transduce intracellular signals through phosphorylation of cytoplasmic proteins in EPO-treated HEL cells.Both STAT1 and STAT5 in this cell line are tyrosine-phosphorylated and translocated to nucleus following the dinding of EPO to HEL cells.Furthermore,the dinding of both STAT1 and STAT5 proteins to specific DNA elements(SIE and PIE elements) is revealed in an EPO-dependent manner,Our data demonstrate that the pathway of signal transduction following the binding of EPO to HEL cells is similar to immature eryhroid cell from the spleen of mice infected with anemia strain of Friend virus.     

Effect of Ethidium Bromide on the Oxidative Metabolism and Enzyme Profiles of Crithidia fasciculata*

SYNOPSIS. Changes in the metabolism of Crithidia fasciculata ATCC 11745 when grown in the presence of ethidium bromide were studied. Ethidium bromide-grown cells had decreased respiratory activity as measured by oxygen consumption. More than 50% of the organisms cultivated in a defined medium containing 1.0 mg/liter of ethidium bromide became dyskine-toplastic and had decreased activities of particulate succinate and NADH-linked dehydrogenases as well as of soluble isocitrate dehydrogenase. These cells also had increased activities of particulate α-glycerophosphate dehydrogenase, soluble α-glycerophosphate dehydrogenase, malic enzyme, hexokinase, and malate dehydrogenase. Ethidium bromide-grown cells had a lower level of ATP and contained less DNA than cells grown in its absence.     

Effect of allopolyploidy on the activity of selected enzymes inHibiscus

Mature seeds of diploid and tetraploidHibiscus species were analyzed for enzyme activity (alcohol dehydrogenase, malate dehydrogenase, leucine aminopeptidase), total protein content, DNA amount and dry weight. The recently formed tetraploid,H. radiatus, generally had enzyme and protein levels very similar to the sum of its progenitors, while the more ancient speciesH. acetosella had several lower levels. This difference may reflect the greater amount of timeH. acetosella has had to evolve dosage compensations.Michigan Agricultural Experiment Station Journal Article 9665.A part of this research was used to satisfy the requirements ofA. Hoisington for a M.S. degree at the University of South Carolina.     

Estimation of heterozygosity for single-probe multilocus DNA fingerprints

In spite of the increasing application of DNA fingerprinting to natural populations and to the genetic identification of humans, explicit methods for estimation of basic population genetic parameters from DNA fingerprinting data have not been developed. Contributing to this omission is the inability to determine, for multilocus fingerprinting probes, relatively important genetic information, such as the number of loci, the number of alleles, and the distribution of these alleles into specific loci. One of the most useful genetic parameters that could be derived from such data would be the average heterozygosity, which has traditionally been employed to measure the level of genetic variation within populations and to compare genetic variation among different loci. We derive here explicit formulas for both the estimation of average heterozygosity at multiple hypervariable loci and a maximum value for this estimate. These estimates are based upon the DNA restriction-pattern matrices that are typical for fingerprinting studies of humans and natural populations. For several empirical data sets from our laboratory, estimates of average and maximal heterozygosity are shown to be relatively close to each other. Furthermore, variances of these statistics based on simulation studies are relatively small. These observations, as well as consideration of the effect of missing alleles and alternate numbers of loci, suggest that the average heterozygosity can be accurately estimated using phenotypic DNA fingerprint patterns, because this parameter is relatively insensitive to the lack of certain genetic information.      

Genetic mapping of maize streak virus resistance from the Mascarene source. II. Resistance in line CIRAD390 and stability across germplasm

The streak disease has a major effect on maize in sub-Saharan Africa. Various genetic factors for resistance to the virus have been identified and mapped in several populations; these factors derive from different sources of resistance. We have focused on the Réunion island source and have recently identified several factors in the D211 line. A second very resistant line, CIRAD390, was crossed to the same susceptible parent, B73. The linkage map comprised 124 RFLP markers, of which 79 were common with the D211×B73 map. A row-column design was used to evaluate the resistance to maize streak virus (MSV) of 191 F_2:3 families under artificial infestation at two locations: Harare (Zimbabwe) and in Réunion island. Weekly ratings of resistance were taken and disease incidence and severity calculated. QTL analyses were conducted for each scoring date and for the integration over time of the disease scores, of incidence, and of severity. Heritability estimates (71–98%) were as high as for the D211×B73 population. Eight QTLs were detected on chromosomes 1, 2, 3, 5 (two QTLs), 6, 8, and 10. The chr1-QTL explained the highest proportion of phenotypic variation, about 45%. The QTLs on chromosomes 1, 2, and 10 were located in the same chromosomal bin as QTLs for MSV resistance in the D211×B73 population. In a simultaneous fit, QTLs explained together 43–67% of the phenotypic variation. The QTLs on chromosomes 3, 5, and 6 appeared to be specific for one or the other component of the resistance. For the chr3-QTL, resistance was contributed by the susceptible parent. There were significant QTL × environment interactions for some of the variables studied, but QTLs were stable in the two environments. They also appeared to be stable over time. Global gene action ranged from partial dominance to overdominance, except for disease severity. Some additional putative QTLs were also detected. The major QTL on chromosome 1 seemed to be common to the other sources of resistance, namely Tzi4, a tolerant line from IITA, and CML202 from CIMMYT. However, the distribution of the other QTLs within the genome revealed differences in Réunion germplasm and across these other resistance sources. This diversity is of great importance when considering the durability of the resistance. Received: 15 June 1998 / Accepted: 30 January 1999     

栲树种群的年龄结构及其生长特征

为了了解栲树的更新方式和更新动态,研究了栲树的生长特征和种群年龄结构.结果表明：栲树种群的年龄结构呈“间歇型”,经历了两个死亡高峰,并存在一个长达30年的断层;栲树的生长受光照的影响,具有很强的可塑性;由于林下光照弱且在垂直空间上不存在差异,栲树生长5～8年后进入生长的第1个抑制期,其年高生长速度可小于0.1 m,并可维持10年;栲树生长的第1个抑制期的起始时间对应着种群第1个死亡高峰期的结束时间,而其结束时间对应着种群第2个死亡高峰期的起始时间,表明栲树生长特征是影响其种群年龄结构的关键因素.