ISSN:0192-253X    

DOI:10.1002/dvg.1020100602

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

年代:1989

数据来源: WILEY

摘要:

AbstractBz‐wmis an allele of theBzlocus of maize isolated by McClintock (1962) as a derivative ofbz‐m2It contains aDs1insertion 63 bp upstream of the start of transcription and a 3 bp insertion in the coding region at the site of theAcelement that was present inbz‐m2. Bz‐wmproduces, in the aleurone layer of the endosperm, low amounts (∼1% of wild‐type) of a Bz‐gene encoded UDP‐glucose: flavoid 3‐0‐glucosyltransferase (UFGT) polypeptide with altered thermal stability. Three phenotypically wild‐type derivatives,Bz' (wm)‐1, Bz' (wm)‐2 and Bz' (wm)‐3, were isolated in the presence ofAcand shown to have excised theDs1element but not fully restored UFGT activity in endosperm assays. In the studies reported here, we have further analyzed theseBz'derivatives ofBz‐wmby determining the DNA sequences left behind onDs1excision, and by measuring the amount of UFGT activity and/orBzmRNA conditioned byBz‐wmand theBz'derivatives in different tissues. The data indicate that tissue‐specific differences in expression of theBzgene have been produced in alleles with mutations caused by transposable elementsAcand Ds. These mutations may affect either the amount ofBztranscription or the stability of the UFGT polypeptide. The sequence or spacing in the ‐63 region of theBzpromoter appears to be critical for maximum expression in aleurone and husk but not in p

ISSN:0192-253X    

DOI:10.1002/dvg.1020100603

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

年代:1989

数据来源: WILEY

摘要:

AbstractGenetic inactivation of theSuppressor‐mutator (Spm)element is correlated with methylation of sequences surrounding the element's transcription initiation site. Several stages in the development of the plant have been identified during which element methylation is reproducibly altered. Loss of element methylation occurs during development of the embryo and early in vegetative growth of the tiller. Element methylation increases during vegetative growth and during development of male and female inflorescences. The susceptibility of element methylation to change during development correlates with the genetic stability of the element's phase of activity. Increases in methylation of sites both upstream and downstream of the Spm element's transcription initiation site parallel increases in the genetic stability of the inactive phase. These results strengthen the likelihood that methylation of C residues within specific regions of the element is important in maintaining the element in an inactive phase and is a component of the molecular mechanism that regulates element expression in plant developmen

ISSN:0192-253X    

DOI:10.1002/dvg.1020100604

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

年代:1989

数据来源: WILEY

摘要:

AbstractTransposable elements are well known for their ability to generate large‐ and small‐scale rearrangements of the sequences flanking their insertion sites. These include deletions, inversions, and duplications.Tam3, a transposon from the Snapdragon(Antirrhinum majus), is highly active in the generation of such rearrangements. We have analysed a number of Tam3‐induced rearrangements at thenivea (niv)locus by Southern blotting, cloning, and sequence determination. The data obtained from these analyses have led to an understanding of the mechanisms by which these complex alleles were formed. We have shown that the primary rearrangements usually occur without excision of the element and therefore result from aberrant transposition attempts. Subsequent rearrangements may occur on excision of the element.Finally, we suggest how the analysis of such rearrangements may not only provide information about Tam3 transposition but also show how transposon‐induced rearrangements may influence the structure and function of the genome as

ISSN:0192-253X    

DOI:10.1002/dvg.1020100605

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

年代:1989

数据来源: WILEY

摘要:

AbstractWe have examined effects of mutations created by transposition of theMu1element of maize into genes coding forAdh1 and Sh1, by means of allozyme measurements, DNA and RNA hybridization, cloning, and sequencing. From our analysis of mutant alleles we conclude that the element acts both to reduce steady‐state levels of RNA and to induce aberrant processing of primary transcripts. We also conclude that genetic background can exert considerable influence in determining the degree to whichMuaffects these aspects of gene expressio

ISSN:0192-253X    

DOI:10.1002/dvg.1020100606

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe high frequency of mutations in Mutator stocks of maize is the result of transposition ofMuelements. Nine differentMuelements that share the 220 bpMuterminal inverted repeats have been described.Mulelements have been found inserted into most of the molecularly characterized mutant alleles isolated from Mutator stocks, and most Mutator stocks contain a high number ofMulelements (10‐60). However, it is clear that additionalMuelements, which share theMultermini but have unrelated internal sequences, can also transpose in Mutator stocks. We were interested in comparing the mutation frequency and type of elements that inserted into a particular locus when Mutator stocks with differing numbers ofMulelements were utilized. Furthermore, previous studies with Mu‐induced mutations have demonstrated that the element that inserted most frequently wasMul.Therefore, to try to obtainMuelements different fromMulwe utilized a stock that had a low number (3‐6) ofMulelements as well as a Mutator stock with a more typical number ofMulelements (20‐60).Utilizing both stocks, we isolated numerous mutants at one gene, Bronze1(Bz1), and compared the type of elements inserted. In this paper we report that both the high and lowMu1stocks producedbz1mutants at frequencies characteristic of Mutator stocks, 6.6 and 4.3 ± 10−5, respectively. We describe the isolation of 20 bz1 mutations, and the initial molecular characterization of eight unstable mutations: two from the highMu1stock and six from the lowMu1stock. The six alleles isolated from the lowMu1stock appear to contain deletedMu1elements, and the two alleles isolated from the highMu1stock contain elements very similar toMu1.When the mutants from the lowMu1stocks were examined, it was found that theMu1‐related elements increased from 3‐6 copies to 9‐20 copies in one generation. The high number ofMu1‐related elements was maintained in subsequent out‐crosses. This spontaneous activation and amplification ofMu‐related elements occurred in at least

ISSN:0192-253X    

DOI:10.1002/dvg.1020100607

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

年代:1989

数据来源: WILEY

摘要:

AbstractTheviviparous‐1 (vp1)locus in maize is a developmental gene that controls diverse aspects of the maturation phase of seed development. Mutations ofvp1alter embryo sensitivity to the hormone abscisic acid and block formation of anthocyanin pigment. Molecular cloning of a Robertson Mutator‐induced mutant allele,vp1‐mum‐1, by transposable element tagging has allowed analysis of several transposon‐inducedvp1mutants. In thevp1‐Mcmutation, the gene is disrupted by 4.0 kbp insertion, which results in expression of a 3′ truncated mRNA. Phenotypically, this allele is at least partially functional in causing embryo dormancy, but is ineffective in controlling anthocyanin expression. This result suggests that disruption of the C‐terminal domain of theVp1protein specifically affects regulation of the anthocyanin pathway. A secondMutator‐derived allele,vp1‐mum2, exhibits an unusual form of somatic mutability in which endosperm cells revert from wild‐typevp1expression to a mutant condition. Thevp1‐mum2allele contains a 1.5 kbp Insertion that has no detectable homology to knownMuelements. This element is retained In wild‐type germinal revertants derived fromvp1‐mum2An apparent DNA modification affecting cleavage at an internal Sstl restriction site in the element correlates withvp1‐mum2states that exhibit wild‐typeVp1expression. A model involving mitotic assortment of modified and unmodified DNA strands during development is propo

ISSN:0192-253X    

DOI:10.1002/dvg.1020100608

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

年代:1989

数据来源: WILEY

摘要:

AbstractTheMutatortransposable element system(Mu)of maize has been responsible for the induction of numerous mutable aleurone mutants of maize. Unlike similar mutants induced by other transposable element systems, the mutability of Mu‐induced mutants did not seem initially to be regulated by an independent autonomous or regulator element. However, in a continuing study of two Mu‐induced a1 mutable mutants(a1‐Mum2)anda1‐Mum3, lines have been obtained that give evidence of an independently segregating regulator of somatic mutability. Data from several generations of crossing are presented indicating that intense somatic mutability in many of these stocks is under the control of an independent regulator. However, testing of other lines, which initially gave evidence of the presence of an independent regulator, were negative. Some of these latter lines could be expected to haveMutatorelements that were modified (methylated) at sites recognized by certain restriction endonucleases. Modification ofMuelements, which is known to affect the expression of somatic mutability, might, at times, be responsible for producing conditions that mimic the segregation of an independent regulator. Lines with stable derivatives of thea1‐Mum2anda1‐Mum3can recover intense somatic mutability by crossing with germinally activeMutatorstocks. Thus, activeMutatorlines contain regulator elements and evidence is presented suggesting that such lines have multiple copies of these elements. Most a1‐Mum2anda1‐Mum3stocks segregating for a regulator do not have germinalMutatoractivity. Thus the presence of one or a few putative regulator elements does not necessarily account for the high level of germinal activity in mo

ISSN:0192-253X    

DOI:10.1002/dvg.1020100609

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

年代:1989

数据来源: WILEY

摘要:

AbstractA new allele of the maizeA1gene, a gene required for anthocyanin pigment biosynthesis, was identified in a genetic stock exhibiting a high frequency of chromosome breakage at the second microspore mitosis. This allele,a‐mrh, is unstable in both somatic and germinal tissue when an independent locus,Mrh, is present in the genome.a‐mrhwas molecularly cloned, and a 246 bp DNA insertion with characteristics of a transposable element was identified within the fourth exon of the gene. Southern blot analysis of germinal derivatives ofa‐mrhsuggests that the DNA insertrMrhis excised from the locus when a wild‐type phenotype is restored. Genetic crosses with components of other two‐element mutable systems of maize failed to induce mutability. We therefore conclude thatrMrhis a member of a new, two‐element transposon system of maize. The genetic and molecular characteristics of the elements involved are discussed with respect to stress‐activated transposition, response of an element to developmental signals, and a possible new role of plant transposons in g

ISSN:0192-253X    

DOI:10.1002/dvg.1020100610

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe regulation of excision ofMuelements of theMutatortransposable element family of maize is not well understood. We have used somatic instability ofMureceptor elements from theBronze 1andBronze 2loci to monitor the frequency and the timing of excision ofMuelements in several tissues. We show that spot size in the aleurone of abz2::mu1stock varies between one to approximately 256 cells. This indicates that excision events begin eight divisions prior to full aleurone differentiation and end after the last division of the aleurone. We show that excision is equally biased for late events in all other tissues studied. A locus on chromosome 5 has been identified that affects spot size, possibly by altering the timing ofMuexcision.Using somatic excision as an assay of Mutator activity, we found that activity can change in small sectors of the tassel; however, there are no overall activity changes in the tassel during the period of pollen shedding. We also report the recovery of germinal revertants for thebz1::mu1andbz2::mu1alleles. One of these revertant alleles was characterized by Southern blot analysis and found to be similar to the progenitor of the mutable allele.

ISSN:0192-253X    

DOI:10.1002/dvg.1020100611

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

年代:1989

数据来源: WILEY