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1.
C. A. Atkins 《Plant and Soil》1987,100(1-3):157-169
Summary Nitrogen (N2) fixed by Rhizobium bacteroids in the legume nodule is excreted as ammonia to the surrounding host cell where it is efficiently
assimilated into the amide group of glutamine. Generally glutamine is a minor exported solute of nitrogen, being further metabolised
to asparagine in temperate species and to the ureides, allantoin and allantoic acid in tropical species. These solutes serve
as the principal translocated forms of nitrogen in xylem. Compartmentalisation of the pathways of nitrogen metabolism and
the role of ammonia in regulation of their activity is examined in nodules of both asparagine-forming (Lupinus albus L.) and ureide-forming (Vigna unguiculata L. Walp) symbioses. 相似文献
2.
Herbert N. Arst Jr. David Tollervey Mark X. Caddick 《Molecular & general genetics : MGG》1989,215(2):364-367
Summary The areA
r
-18 mutation is a loss-of-function mutation in areA, the positive acting regulatory gene mediating nitrogen metabolite repression in Aspergillus nidulans. It results from a reciprocal translocation which splits the coding region into 5 and 3 moieties. Surprisingly, we have selected rare intracistronic revertants of areA
r
-18. From crosses heterozygous for areA
r
-18 revertant alleles, duplication-deficiency progeny containing two copies of a substantial portion of chromosome IV but lacking part of chromosome III, including the 5 moiety of areA, have been obtained. For all four revertants analysed genetically, growth properties of these duplication-deficiency strains indicate that the reversion events involve the 3 portion of areA and that the 5 portion of areA is unnecessary for the revertant phenotype. This conclusion was directly confirmed for one revertant using Southern blotting. As all four reversion events involve additional chromosomal rearrangements, they probably fuse functional promoters, ribosome binding sites and in frame initiation codons to the 3 portion of the gene. In the course of characterisation of these mutations, new mapping data for a large region of chromosome IV have been generated, and a new reciprocal translocation activating the cryptic regulatory gene areB, whose product can substitute for that of areA, has been identified. 相似文献
3.
A. M. Figueiras M. A. Elorrieta C. Benito 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1989,78(2):224-228
Summary The progeny of four crosses between a structural heterozygote for a reciprocal translocation and a homozygote for the standard chromosome arrangement were analyzed in rye (Secale cereale L. cv Ailés) for the electrophoretic patterns of eight different leaf and endosperm isozymes and also for the meiotic configuration at metaphase I. The Pgi-1, 6-Pgd-2 and Mdh-1 loci are linked to each other and also to the reciprocal translocation. These loci have been located on chromosome 1R. The Mdh-1 locus is located in the interstitial segment of chromosome 1R, between the centromere and the breakpoint. The Pgm-1 locus has been located on chromosome arm 4RS and is linked to Pgi-1, 6-Pgd-2, Mdh-1 and the reciprocal translocation. The estimated distance between the Pgm-1 locus and the centromere is 14.98 ± 2.27 cM. Therefore, the reciprocal translocation involves the 1R and 4R chromosomes. Other linked loci detected have been Mdh-2b and Est-2 (7.40 ± 2.90 cM) and Got-3 and Est-2 (5.62 ± 3.07 cM). These three last loci are located on chromosome 3R and their order most probably is Mdh-2b — Est-2 — Got-3. 相似文献
4.
Summary
Lathyrus sylvestris is a pioneer legume often found in disturbed habitats. Mainly reproduced through vegetative propagation, this clonal species presents a system of ramets that remain connected for several years. The existence of carbon transfer among ramets within a clone has been studied using 14C in situ. Assimilate translocation from primary to secondary ramets was observed in all clones when the primary ramet was exposed to 14CO2. The amount of transfer ranged from trace up to 90% of the total 14C incorporated. However, in only half of the clones there was consistent enrichment of the secondary ramet (5 to 89%) suggesting that interramets transfer of carbon may be facultative. Furthermore, when significant export occurred from the primary ramet, it was always principally towards only one ramet even when the clone included more than one. The transfer of 14C from secondary to primary ramets was shown to be significant only when photosynthesis of the latter was decreased by shading. In this case import of carbon was never more than 60% of the incorporated 14C.No correlation was found between age or size of the ramets and the intensity of transfer. The shading effect let suppose that transfers are mainly driven by carbon limitation due to changing environmental conditions and not to the state of ramet maturity. The adaptative advantage of such facultative physiological integration between ramets of a clone is discussed. 相似文献
5.
一个1B/1R小麦-黑麦染色体易位的鉴定 总被引:2,自引:2,他引:0
本研究对冬小麦品系73(36)9-1的1B/1R易位染色体进行了遗传分析。发现73(36)9-1有一对随体染色体,它的两个亲本矮丰四号及洛夫林10(Lovrin lo)分别有两对和一对随体染色体。观察用矮丰四号回交的F_1,绝大部分花粉母细胞的中期染色体都能正常配对,而用洛夫林10回交的,除了多数产生两个单价体之外,正常配对的情况也能经常看到。同时还发现,73(36)9-1和“中国春”双端体(CSDT)的1BL能很好地配对并形成一个棒状的异形二价体,而它和CSDT 1BS的染色体则主要产生20″+1′+t′的构型,从而证明易位发生在1B染色体的短臂,并且该易位的片段来自黑麦染色体1RL。本文还讨论了该易位发生的可能途径,推断是由于在F_1花粉母细胞中的两个单价体(一个是小麦染色体1B,一个是黑麦染色体1R)同时进行错分裂之后产生的两种端着丝点染色体(1BL和1RL)重新并合形成的,因而冬小麦73(36)9-1可能是一个自发产生的易位系。 相似文献
6.
S. Hinnisdaels L. Bariller A. Mouras V. Sidorov J. Del-Favero J. Veuskens I. Negrutiu M. Jacobs 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1991,82(5):609-614
Summary Extremely asymmetric nuclear hybrids have been obtained via protoplast fusion in an intergeneric combination. Irradiated (cobalt60,100 krad) kanamycinresistant Petunia hybrida mesophyll protoplasts were chemically fused with wild-type mesophyll protoplasts of Nicotiana plumbaginifolia. Eighty-six hybrid colonies were selected on kanamycin-containing medium, and twenty-four of these could be induced to regenerate numerous shoots. Cytological analysis of the regenerants showed the presence of a few chromosome fragments in some lines, and even a metacentric chromosome in yet another line. Besides additional chromosome fragments some lines only possessed typical Nicotiana chromosomes, and this at the diploid (2n = 2X = 20) as well as the tetraploid (2n = 2X = 40) level. Biochemical analysis showed that all regenerants had neomycin phosphotransferase activity (NPTII), which suggests that intergenomic recombination and or translocation events took place at least in those lines where no additional chromosome fragments could be detected. The presence of the NPTII gene was shown by Southern hybridization. All regenerants tested were fertile, and the segregation ratios for the kanamycin gene (for self and backcross pollinations to the recipient partner) for some of the regenerants correspond with Mendelian rules for a monogenic dominant marker. Most of the regenerants showed abnormal segregation ratios; in this case, no correlation could be made between segregation ratio and chromosome composition.Our results demonstrate the existence of intergenomic recombination and translocations evens in nuclear somatic hybrid plants obtained via gamma-fusion. 相似文献
7.
D. Christine Sigurdson Robert K. Herman Cynthia A. Horton Claire K. Kari Steven E. Pratt 《Molecular & general genetics : MGG》1986,202(2):212-218
Summary The translocation mnT12(IV;X) is a fusion of holocentric chromosomes IV and X, the breakpoints occurring near the left end of IV and the right end of X. Animals homozygous for mnT12 are viable and fertile; they contain five pairs of chromosomes rather than the normal set of six pairs. The mnT12 chromosome is larger than all wild-type chromosomes and thus identifies linkage groups IV and X cytologically. Hermaphrodites heterozygous for mnT12 show high frequency meiotic nondisjunction both between mnT12 and the X chromosome, which results in a high incidence of male self progeny (27% compared to the wild-type incidence of 0.2%), and between mnT12 and chromosome IV, which results in a high incidence of self progeny essentially trisomic for chromosome IV (karyotype IV/mnT12/mnT12). The viability of chromosome IV trisomics has been confirmed by constructing animals trisomic for only normal copies of chromosome IV; these animals are morphologically wild type. Meiotic chromosome disjunction in mnT12 homozygotes appears to be normal, although the frequency of recombination between markers that are normally X-linked is significantly reduced. Males of genotype IV/mnT12/0 are fertile. They can be thought of as having a neo-X(mnT12) neo-Y(normal IV) karyotype since it is possible to maintain a male-hermaphrodite stock of C. elegans consisting of such males and hermaphrodites carrying two neo-X chromosomes and no neo-Y; the organism is thus converted from an XO:XX type of sex determination to an XX:XX system. 相似文献
8.
Root turnover and production by14C dilution: implications of carbon partitioning in plants 总被引:1,自引:1,他引:0
D. G. Milchunas W. K. Lauenroth J. S. Singh C. V. Cole H. W. Hunt 《Plant and Soil》1985,88(3):353-365
Summary Estimates of belowground net primary production (BNP) obtained by using traditional soil core harvest data are subject to a variety of potentially serious errors. In a controlled growth chamber experiment, we examined the aboveground-belowground, labile to structural tissue, and plant to soil dynamics of carbon to formulate a14C dilution technique for potential successful application in the field and to quantify sources of error in production estimates.Despite the fact that the majority of net14C movement between above- and belowground plant parts occurred between the initial labeling and day 5, significant quantities of14C were incorporated into cell-wall tissue throughout the growing period. The rate of this increase at late sampling dates was greater for roots than for shoots. Total loss of assimilated14C was 47% in wheat and 28% in blue grama. Exudation and sloughing in wheat and blue grama, respectively, was 15 and 6% of total uptake and 22 and 8% of total plant production.When root production estimates by14C dilution were corrected for the quantities of labile14C incorporated into structural carbon between two sampling dates, good agreement with actual production was found. The error associated with these estimates was ±2% compared with a range of –119 to –57% for the uncorrected estimates. Our results suggest that this technique has potential field application if sampling is performed the year after labelling.Sources of errors in harvest versus14C dilution estimates of BNP are discussed. 相似文献
9.
Pruned source-sink transport systems from predarkened plants of Amaranthus caudatus L. and Gomphrena globosa L. were used to study the localization of 14C-labeled photosynthate imported into experimentally induced sink leaves by microautoradiography. During a 6-h (Amaranthus) or a 4-h (Gomphrena) transport period, 14C-assimilates were translocated acropetally from a mature source leaf provided with 14CO2, into a younger induced sink leaf (dark/-CO2). In addition, a young still-expanding source leaf exposed to 14CO2 exported 14C-assimilates basipetally into a mature induced sink leaf (dark/-CO2). Microautoradiographs showed that imported 14C-photosynthate was strongly accumulated in the sieve element/companion cell complexes of midveins, secondary veins, and minor veins of both the mature and the expanding sink leaf. Some label was also present in the vascular parenchyma and bundlesheath cells. In petioles, 14C-label was concentrated in the sieve element/companion cell complexes of all bundles indicating that assimilates were imported and distributed via the phloem. Moreover, a considerable amount of radioactivity unloaded from the sieve element/companion cell complexes of petiolar bundles, was densely located at sites of secondary wall thickenings of differen-tiating metaxylem vessels, and at sites of chloroplasts of the vascular parenchyma and bundle-sheath cells. These observations were more striking in petioles of Gomphrena than Amaranthus.Abbreviation se/cc
sieve element/companion cell 相似文献
10.
Decreased Protein Kinase C Activity During Cerebral Ischemia and After Reperfusion in the Adult Rat 总被引:6,自引:4,他引:2
R. Christian Crumrine George Dubyak Joseph C. LaManna† 《Journal of neurochemistry》1990,55(6):2001-2007
The possible activation of protein kinase C (PKC) during total cerebral ischemia was investigated in the rat. Translocation of PKC activity from the soluble to the particulate fraction was used as an index of PKC activation. There was a drop in the proportion of particulate PKC activity from 30% for controls to 20% by 30 min of ischemia (p less than 0.01). By 20 min of cardiac arrest, there was a 40% decline of the total cellular PKC activity (p less than 0.01). This was not accompanied by an increase in activator-independent activity, a finding indicating PKC was not being converted to protein kinase M. These data suggest that PKC was not activated during ischemia, but rather that ischemia causes a reduction in cellular PKC activity. Translocation of PKC activity to the particulate fraction was not observed in the cerebral cortex or hippocampus of reperfused brain for up to 6 h of recovery following 11-13 min of total cerebral ischemia. The level of total, soluble, and particulate PKC activity in the cerebral cortex was reduced (p less than 0.05), corresponding to the decrease observed by 15 min of ischemia without reflow. A similar decline in activity was also observed in the hippocampus. No increase in activator-independent activity was observed. These data suggest that PKC was inhibited during cerebral ischemia and that this reduced level of PKC activity was maintained throughout 6 h of recovery. We conclude that pathological activation of PKC was not responsible for the evolution of ischemic brain damage. 相似文献