Biochemical and Genetic Evidence for Participation of DevR in a Phosphorelay Signal Transduction Pathway Essential for Heterocyst Maturation in Nostoc punctiforme ATCC 29133

In a test of the hypothesis that DevR is a response regulator protein that functions in a phosphorelay signal transduction system involved in heterocyst development in Nostoc punctiforme ATCC 29133, purified affinity-tagged DevR was shown to be phosphorylated in vitro by the noncognate sensor kinase EnvZ. Site-directed mutagenesis was used to generate N. punctiforme mutants with single amino acid substitutions at the putative phosphorylation site of DevR. These mutants exhibited a Fox- phenotype like the original devR insertion mutant UCD 311, consistent with a phosphotransferase role for DevR.     

A quantitative trait locus for live weight maps to bovine Chromosome 23

A multiple-marker mapping approach was used to search for quantitative trait loci (QTLs) affecting production, health, and fertility traits in Finnish Ayrshire dairy cattle. As part of a whole-genome scan, altogether 469 bulls were genotyped for six microsatellite loci in 12 families on Chromosome (Chr) 23. Both multiple-marker interval mapping with regression and maximum-likelihood methods were applied with a granddaughter design. Eighteen traits, belonging to 11 trait groups, were included in the analysis. One QTL exceeded experiment level and one QTL genome level significance thresholds. Across-families analysis provided strong evidence (P_experiment= 0.0314) for a QTL affecting live weight. The QTL for live weight maps between markers BM1258 and BoLA DRBP1. A QTL significant at genome level (P_genome= 0.0087) was mapped for veterinary treatment, and the putative QTL probably affects susceptibility to milk fever or ketosis. In addition, three traits exceeded the chromosome 5% significance threshold: protein percentage of milk, calf mortality (sire), and milking speed. In within-family analyses, protein percentage was associated with markers in one family (LOD score = 4.5). Received: 14 December 1998 / Accepted: 28 March 1998     

Total gene deletions and mutant frequency of the HPRT gene as indicators of radiation exposure in Chernobyl liquidators

This study was conducted to determine the utility of deletion spectrum and mutant frequency (MF) of the hypoxanthine phosphoribosyl transferase gene (HPRT) as indicators of radiation exposure in Russian Liquidators who served in 1986 or 1987 in the clean up effort following the nuclear power plant accident at Chernobyl. HPRT MF was determined using the cloning assay for 117 Russian Controls and 122 Liquidators whose blood samples were obtained between 1991 and 1998. Only subjects from whom mutants were obtained for deletion analysis are included. Multiplex PCR analysis was performed on cell extracts of 1080 thioguanine resistant clones from Controls and 944 clones from Liquidators. Although the deletion spectra of Liquidators and Controls were similar overall, the Liquidator deletion spectrum was heterogeneous over time. Most notable, the proportion of total gene deletions was higher in 1991–1992 Liquidators than in Russian Controls (χ²=10.5, p=0.001) and in 1993–1994 Liquidators (χ²=8.3, p=0.004), and was marginally elevated relative to 1995–1996 Liquidators (χ²=3.3, p=0.07). This type of mutation has been highly associated with radiation exposure. Total gene deletions were not increased after 1992. Band shift mutations were also increased in the 1991–1992 Liquidators but were associated with increased MF of both Liquidators and Controls (p=0.009), not with increased MF in 1991–1992 Liquidators (p=0.7), and hence are not believed to be associated with radiation exposure. Regression analysis demonstrated that relative to Russian Controls HPRT MF was elevated in Liquidators overall when adjusted for age and smoking status (37%, p=0.0001), and also was elevated in Liquidators sampled in 1991–1992 (72%, p=0.0076), 1993–1994 (22%, p=0.037), and 1995–1996 (62%, p=0.0001). In summary, HPRT MF was found to be the more sensitive and persistent indicator of radiation exposure, but the specificity of total gene deletions led to detection of probable heterogeneity of radiation exposure within the exposed population.     

Soluble proteins and dehydrins in nitrogen-fertilized Scots pine seedlings during deacclimation and the onset of growth

Deacclimation of Scots pine ( Pinus sylvestris ) in northern Finland (65°N) was studied from the perspective of protein metabolism, which was related to nitrogen fertilization. Two-year-old seedlings were fertilized with calcium ammonium nitrate (0, 442 and 884 kg N ha⁻¹) in the summer prior to the study. Needles were harvested for analyses at 3-week intervals during the natural deacclimation period from mid-March to the beginning of June 1998. Deacclimation was followed by monitoring various physiological variables: freezing resistance decreased and osmotic potential increased during the experiment and needle dry weight increased from bud flushing onwards. The concentration of soluble proteins in needles was higher in fertilized seedlings but decreased transiently in the 884 kg N ha⁻¹ fertilized seedlings before budbreak. The abundance of several small polypeptides (17–32 kDa) decreased in the spring. A 60-kDa protein, identified by immunoblotting as a dehydrin, was detected in all treatments. The quantity of this dehydrin decreased with resumption of growth, along with the appearance of 50- and 56-kDa dehydrins. The concentration of these dehydrins decreased during dehardening more rapidly in fertilized seedlings than in the control plants. The fertilized seedlings started to grow earlier than the unfertilized plants. In conclusion, nitrogen fertilization provided good reserves for new growth but did not affect deacclimation of pine needles.     

Large-scale grazing history effects on Arctic-alpine germinable seed banks

Grazing constitutes a selective pressure on vegetation recruitment through modification of the seed banks. Here we address changes in seed bank density and its life history trait composition in century-old pastures, where contrasting reindeer densities have developed during the last decades. We cover the actual scales used by these wide-roaming herbivores by sampling 70 productive tundra habitats over 7,421 km² in the reindeer summer pastures of Northern Norway. Results showed that the seed bank density was significantly lowered where reindeer densities had increased in recent decades, whereas the century-long history of grazing probably explains the main seed bank traits typical of grazing tolerant plants. The dominant trait characteristics were small seeds (<0.5 mg), seeds lacking dispersal mechanism and individuals with a graminoid growth form. Finally, differences between regions introduced trait variation independent of grazing history, reinforcing the importance of using scales covering several contexts when designing ecological studies.     

Effects of phenoxy acid herbicides and glyphosate on nitrogenase activity (acetylene reduction) in root-associated Azospirillum, Enterobacter and Klebsiella

Abstract Nitrogenase activity (C₂H₂ reduction) in root-associated Azospirillum lipoferum, Klebsiella pneumoniae, Enterobacter agglomerans and Pseudomonas sp. isolated from roots of Finnish grasses was assayed in the presence of glyphosate, the phenoxy acid herbicides 2-methyl-4-chlorophenoxy acetic acid (MCPA), 2,4-dichlorophenoxy acetic acid (2,4-D), (±)-2-(2-methyl-4-chlorophenoxy)propionic acid (mecoprop) and (±)-2-(2,4-dichlorophenoxy)propionic acid (dichlorprop), and the commercial products Roundup, Nurmikko-Hedonal, Mepro, and Dipro. In the presence of the phenoxy acid herbicides the nitrogenase activity of K. pneumoniae was significantly inhibited, but that of E. agglomerans was stimulated. With the exception of Mepro and mecoprop no phenoxy acid herbicides inhibited the nitrogenase activity of A. lipoferum and none that of Pseudomonas sp. Nurmikko-Hedonal considerably stimulated the nitrogenase activity of E. agglomerans , and Pseudomanas sp. On the other hand, the nitrogenase activity of both K. pneumoniae and E. agglomerans was considerably repressed by glyphosate and Roundup, which also inhibited the growth of the bacteria. These chemicals had no effect on the growth of A. lipoferum and Pseudomonas sp., but stimulated their nitrogenase activity.     

Pellets of proof: First glimpse of the dietary composition of adult odonates as revealed by metabarcoding of feces

Recent advances in molecular techniques allow us to resolve the diet of unstudied taxa. Odonates are potentially important top‐down regulators of many insects. Yet, to date, our knowledge of odonate prey use is based mainly on limited observations of odonates catching or eating their prey. In this study, we examine the potential use of metabarcoding in establishing the diet of three adult odonate species (Lestes sponsa, Enallagma cyathigerum, and Sympetrum danae) at a site in southwestern Finland. To this purpose, we compared three different methods for extracting DNA from fecal samples: the Macherey‐Nagel Nucleospin XS kit, a traditional salt extraction, and the Zymo Research Fecal Microprep kit. From these extracts, we amplified group‐specific mitochondrial markers (COI and 16S rRNA) from altogether 72 odonate individuals, and compared them to comprehensive reference libraries. The three odonate species show major overlap in diet, with no significant differences between individuals of different size and/or gender, reflecting opportunistic foraging of adult odonates. Of a total of 41 different prey species detected, the most frequently consumed ones were Diptera, with additional records of six other orders. Based on our data, the best DNA extraction method is the traditional salt extraction, as it provides the most information on prey content while also being the most economical. To our knowledge, this is the first study to resolve the species‐level diet of adult odonates. Armed with the appropriate methodological caveats, we are ready to examine the ecological role of odonates in both terrestrial and aquatic food webs, and in transferring subsidies between these two realms.     

不同火灾强度下森林植被的自然恢复

按照与火灾发生区的方位将森林划分为火灾核心区、火灾边缘区、地下火发生以及对照(未发生火灾)等四类;同时,按照树种将其划分为兴安落叶松纯林、白桦纯林及兴安落叶松、白桦混交林等三类,对阿尔山地区1998年"5.13"雷击火发生迹地林下植被的自然恢复状况进行了调查.结果表明:提出的分级标准能够反映林分遭受不同强度火灾后植被恢复状况的差异.火灾核心区受害程度最重,在物种丰富度、物种多样性、灌草地上生物量等方面均居于最低水平;地下火发生区林受害部分多在地下,各项指标位居次要地位;火灾边缘区林分虽受到一定的危害,但各项指标在所有受害林分中居最高水平.不同程度受害区域内的乔灌木年轮数呈现随危害程度增加而减少的趋势.混交林的恢复力强于纯林,兴安落叶松也显示了比白桦更强的恢复力.通过林下阳性植物与阴性植物代表种相对盖度的比值变化,对林下植被的灾后演替进行了研究,结果表明,火灾核心区林位于林窗阶段,地下火发生林处于建立阶段,而火灾边缘区林与对照均处于成熟阶段.对火灾后的人工改善措施进行探讨.文章提出从年轮的宽度与分布规律、林分初级生产力与灌草地上生物量的关系及林分节肢动物群落等方面做深入分析.