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1.
Maintenance of the cellobiose utilization genes of Escherichia coli in a cryptic state 总被引:6,自引:1,他引:5
The genes for cellobiose utilization are normally cryptic in Escherichia
coli. The cellobiose system was used as a model to understand the process
by which silent genes are maintained in microbial populations. Previously
reported was (1) the isolation of a mutant strain that expresses the
cellobiose-utilization (Cel) genes and (2) that expression of those genes
allows utilization of three beta- glucoside sugars: cellobiose, arbutin,
and salicin. The Cel gene cluster has now been cloned from that mutant
strain. In the course of locating the Cel genes within the cloned DNA
segment, it was discovered that inactivation of the Cel-encoded hydrolase
rendered the host strain sensitive to all three beta-glucosides as potent
inhibitors. This sensitivity arises from the accumulation of the
phosphorylated beta- glucosides. Because even the fully active genes
conferred some degree of beta-glucoside sensitivity, the effects of
cellobiose on a series of five Cel+ mutants of independent origin were
investigated. Although each of those strains utilizes cellobiose as a sole
carbon and energy source, cellobiose also acts as a potent inhibitor that
reduces the growth rate on glycerol 2.5-16.5-fold. On the other hand,
wild-type strains that cannot utilize cellobiose are not inhibited. The
observation that the same compound can serve either as a nutrient or as an
inhibitor suggests that, under most conditions in which cellobiose will be
present together with other resources, there is a strong selective
advantage to having the cryptic (Cel0) allele. In those environments in
which cellobiose is the sole, or the best, resource, mutants that express
the genes (Cel+) will have a strong selective advantage. It is suggested
that temporal alternation between these two conditions is a major factor in
the maintenance of these genes in E. coli populations. This alternation of
environments and fitnesses was predicted by the model for cryptic-gene
maintenance that was previously published.
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2.
Selection-induced mutations are nonrandom mutations that occur as specific
and direct responses to environmental challenge. Examples of
selection-induced mutations have been reported both in bacteria and in
yeast. I previously showed (Hall 1988) that excisions of the mobile genetic
element IS150 from within bglF are selection induced and argued that they
occurred because they were potentially advantageous under the selective
conditions employed. Mittler and Lenski (Mittler and Lenski 1992) have
argued that such excisions are not selection induced but that they occur
randomly in nondividing cells. Here I provide further evidence that IS150
excisions are induced by selection and that the excisions are immediately,
rather than only potentially, advantageous to the cell. I also provide
evidence that excisions, which Mittler and Lenski claim occur randomly in
saturated broth cultures, actually occur after samples from those cultures
are plated onto selective medium.
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3.
Ganeshan Seedhabadee Båga Monica Harvey Bryan L. Rossnagel Brian G. Scoles Graham J. Chibbar Ravindra N. 《Plant Cell, Tissue and Organ Culture》2003,73(1):57-64
The in vitro plant regeneration frequencies for immature scutella, leaf-bases/apical meristems (LB/AM) and mature embryos of four commercially important barley genotypes were compared. Production of shoots from mature embryos or calluses of LB/AM incubated on media containing 1.0 or 2.0 mg l–1 6-benzylaminopurine (BA) were comparable to regeneration frequencies obtained for scutella-derived calluses of the same genotypes. Incubation of excised mature embryos and LB/AM on media containing the plant growth regulator, thidiazuron (TDZ), resulted in an increased shoot production. However, TDZ treatment did not stimulate plant regeneration from calluses derived from scutella or LB/AM. Shoots formed from TDZ-treated mature embryos and LB/AM were induced without a callus interphase and the in vitro culture system gave a three- to eight-fold higher regeneration frequency than recorded for scutella-derived calluses on BA medium. The simplicity and rapid development of shoots using the mature embryo system could potentially be used for the regeneration and genetic transformation of barley over alternative regeneration systems. 相似文献
4.
High-level expression of the Endo-beta-N-acetylglucosaminidase F2 gene in E.coli: one step purification to homogeneity 总被引:1,自引:0,他引:1
The Endo F2gene was overexpressed in E.coli as a fusion protein joined to
the maltose-binding protein. MBP-Endo F2was found in a highly enriched
state as insoluble, inactive inclusion bodies. Extraction of the inclusion
bodies with 20% acetic acid followed by exhaustive dialysis rendered the
fusion protein active and soluble. MBP-Endo F2was digested with Factor
Xaand purified on Q-Sepharose. The enzyme was homogeneous by SDS-PAGE, and
appeared as a single symmetrical peak on HPLC. Analysis of the
amino-terminus demonstrated conclusively that recombinant Endo F2was
homogeneous and identical to the native enzyme.
相似文献
5.
Vicky Roslinsky Peter E. Eckstein Victor Raboy Brian G. Rossnagel Graham J. Scoles 《Molecular breeding : new strategies in plant improvement》2007,20(4):323-330
Phytate is the primary form of phosphorus found in mature cereal grain. This form of phosphorus is not available to monogastric
animals due to a lack of the enzyme phytase in their digestive tract. Several barley low
phytic
acid (lpa) mutants have been identified that contain substantial decreases in seed phytate accompanied by concomitant increases in
inorganic phosphorus. Seed homozygous for low phytic acid
1-1 (lpa1-1) or low phytic acid
2-1 (lpa2-1) has a 50% and 70% decrease in seed phytate respectively. These mutations were previously mapped to chromosomes 2HL and 7HL
respectively. The RFLP marker ABC153 located in the same region of 2H was converted to a sequence-characterized-amplified-region
(SCAR) marker. Segregation analysis of the CDC McGwire × Lp422 doubled haploid population confirmed linkage between the SCAR
marker and the lpa1-1 locus with 15% recombination. A third low phytic acid mutant, M635, has a 75% decrease in phytate. This mutation was located
to chromosome 1HL by linkage with an inter-simple sequence repeat (ISSR) based marker (LP75) identified through bulked-segregant
analysis, and has been designated lpa3-1. Based on analysis of recombination between marker LP75 and low phytic acid in an additional mutant line M955 (95% phytate
decrease), lpa3-1 and the mutation in M955 are in the same region on chromosome 1HL, and may be allelic. 相似文献
6.
In vitro regeneration of cereals based on multiple shoot induction from mature embryos in response to thidiazuron 总被引:1,自引:0,他引:1
Seedhabadee Ganeshan Sanjay V. Chodaparambil Monica B?ga D. Brian Fowler Pierre Hucl Brian G. Rossnagel Ravindra N. Chibbar 《Plant Cell, Tissue and Organ Culture》2006,85(1):63-73
The in vitro competency of mature cereal embryos (winter, spring and durum wheats, oat, barley and triticale) was assessed for direct
multiple shoot production on culture media containing the plant growth regulators, thidiazuron (TDZ) and/or 6–benzylaminopurine
(BAP). Mature embryos of CDC Dancer oat showed the best response, with 69 shoots per explant on culture medium containing
a combination of 4.5 μM TDZ and 4.4 μM BAP. TDZ alone induced about 16 shoots per explant from the oat. Among the wheat genotypes,
durum wheat showed the most number of shoots (35) per explant on culture medium containing 4.5 μM of TDZ and 4.4 μM of BAP.
With TDZ alone, shoot regeneration for durum wheat ranged from 27–32 shoots per explant. The regeneration frequency from the
three winter wheat genotypes ranged from 11–25 shoots per explant and was highest on culture medium containing 9.1 μM TDZ
and 4.4 μM BAP. The latter culture medium was also effective for a triticale genotype, inducing 34 shoots per explant. The
regeneration from mature embryos of barley genotypes ranged from 5–9 shoots per explant. The mature embryos of all the cereals
tested could be used for in vitro regeneration with TDZ and TDZ+BAP combinations. 相似文献
7.
L. A. Marquez-Cedillo P. M. Hayes A. Kleinhofs W. G. Legge B. G. Rossnagel K. Sato S. E. Ullrich D. M. Wesenberg 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,103(4):625-637
A better understanding of the genetics of complex traits, such as yield, may be achieved by using molecular tools. This study
was conducted to estimate the number, genome location, effect and allele phase of QTLs determining agronomic traits in the
two North American malting barley (Hordeum vulgare L.) quality variety standards. Using a doubled haploid population of 140 lines from the cross of two-rowed Harrington×six-rowed
Morex, agronomic phenotypic data sets from nine environments, and a 107-marker linkage map, we performed QTL analyses using
simple interval mapping and simplified composite interval mapping procedures. Thirty-five QTLs were associated, either across
environments or in individual environments, with five grain and agronomic traits (yield, kernel plumpness, test weight, heading
date, and plant height). Significant QTL×environment interaction was detected for all traits. These interactions resulted
from both changes in the magnitude of response and changes in the sign of the allelic effect. QTLs for multiple traits were
coincident. The vrs1 locus on chromosome 2 (2H), which determines inflorescence row type, was coincident with the largest-effect QTL determining
four traits (yield, kernel plumpness, test weight, and plant height). QTL analyses were also conducted separately for each
sub-population (six-rowed and two-rowed). Seven new QTLs were detected in the sub-populations. Positive transgressive segregants
were found for all traits, but they were more prevalent in the six-rowed sub-population.QTL analysis should be useful for
identifying candidate genes and introgressing favorable alleles between germplasm groups.
Received: 18 August 2000 / Accepted: 15 December 2000 相似文献
8.
Persistent nuclear ribosomal DNA sequence polymorphism in the Amelanchier agamic complex (Rosaceae) 总被引:5,自引:0,他引:5
Campbell CS; Wojciechowski MF; Baldwin BG; Alice LA; Donoghue MJ 《Molecular biology and evolution》1997,14(1):81-90
Individual plants of several Amelanchier taxa contain many polymorphic
nucleotide sites in the internal transcribed spacers (ITS) of nuclear
ribosomal DNA (nrDNA). This polymorphism is unusual because it is not
recent in origin and thus has resisted homogenization by concerted
evolution. Amelanchier ITS sequence polymorphism is hypothesized to be the
result of gene flow between two major North American clades resolved by
phylogenetic analysis of ITS sequences. Western North American species plus
A. humilis and A. sanguinea of eastern North America form one clade (A),
and the remaining eastern North American Amelanchier make up clade B. Five
eastern North American taxa are polymorphic at many of the nucleotide sites
where clades A and B have diverged and are thought to be of hybrid origin,
with A. humilis or A. sanguinea as one parent and various members of clade
B as the other parent. Morphological evidence suggests that A. humilis is
one of the parents of one of the polymorphic taxa, a microspecies that we
refer to informally as A. "erecta." Sequences of 21 cloned copies of the
ITS1- 5.8S gene-ITS2 region from one A. "erecta" individual are identical
to A. humilis sequence or to the clade B consensus sequence, or they are
apparent recombinants of A. humilis and clade B ITS repeats. Amelanchier
"erecta" and another polymorphic taxon are suspected to be relatively old
because both grow several hundred kilometers beyond the range of one of
their parents. ITS sequence polymorphisms have apparently persisted in
these two taxa perhaps because of polyploidy and/or agamospermy (asexual
seed production), which are prevalent in the genus.
相似文献
9.
Lysine acetylome profiling uncovers novel histone deacetylase substrate proteins in Arabidopsis 下载免费PDF全文
Paul J Boersema Jan‐Oliver Jost Katharina Kramer Ahmet Bakirbas Julia Sindlinger Magdalena Plöchinger Dario Leister Glen Uhrig Greg BG Moorhead Jürgen Cox Michael E Salvucci Dirk Schwarzer Matthias Mann Iris Finkemeier 《Molecular systems biology》2017,13(10)
Histone deacetylases have central functions in regulating stress defenses and development in plants. However, the knowledge about the deacetylase functions is largely limited to histones, although these enzymes were found in diverse subcellular compartments. In this study, we determined the proteome‐wide signatures of the RPD3/HDA1 class of histone deacetylases in Arabidopsis. Relative quantification of the changes in the lysine acetylation levels was determined on a proteome‐wide scale after treatment of Arabidopsis leaves with deacetylase inhibitors apicidin and trichostatin A. We identified 91 new acetylated candidate proteins other than histones, which are potential substrates of the RPD3/HDA1‐like histone deacetylases in Arabidopsis, of which at least 30 of these proteins function in nucleic acid binding. Furthermore, our analysis revealed that histone deacetylase 14 (HDA14) is the first organellar‐localized RPD3/HDA1 class protein found to reside in the chloroplasts and that the majority of its protein targets have functions in photosynthesis. Finally, the analysis of HDA14 loss‐of‐function mutants revealed that the activation state of RuBisCO is controlled by lysine acetylation of RuBisCO activase under low‐light conditions. 相似文献
10.
Elke M Lohmeier-Vogel David Kerk Mhairi Nimick Susan Wrobel Lori Vickerman Douglas G Muench Greg BG Moorhead 《BMC plant biology》2008,8(1):120