scholarly journals A separation-of-function ZIP4 wheat mutant allows crossover between related chromosomes and is meiotically stable

2021 ◽  
Author(s):  
Azahara C. Martín ◽  
Abdul Kader Alabdullah ◽  
Graham Moore
Keyword(s):  
Wheat Breeding ◽  
Wild Type ◽  
Grain Number ◽  
Homologous Chromosomes ◽  
Chromosome 5B ◽  
Correct Pairing ◽  
New Gene ◽  
Multiple Genomes ◽  
Mutant Lines ◽  
Homoeologous Chromosomes

ABSTRACTMany species, including most flowering plants, are polyploid, possessing multiple genomes. During polyploidisation, fertility is preserved via the evolution of mechanisms to control the behaviour of these multiple genomes during meiosis. On the polyploidisation of wheat, the major meiotic gene ZIP4 duplicated and diverged, with the resulting new gene TaZIP4-B2 being inserted into chromosome 5B. Previous studies showed that this TaZIP4-B2 promotes pairing and synapsis between wheat homologous chromosomes, whilst suppressing crossover between related (homoeologous) chromosomes. Moreover, in wheat, the presence of TaZIP4-B2 preserves up to 50% of grain number. The present study exploits a ‘separation-of-function’ wheat Tazip4-B2 mutant named zip4-ph1d, in which the Tazip4-B2 copy still promotes correct pairing and synapsis between homologues (resulting in the same pollen profile and fertility normally found in wild type wheat), but which also allows crossover between the related chromosomes in wheat haploids of this mutant. This suggests an improved utility for the new zip4-ph1d mutant line during wheat breeding exploitation, compared to the previously described CRISPR Tazip4-B2 and ph1 mutant lines. The results also reveal that loss of suppression of homoeologous crossover between wheat chromosomes does not in itself reduce wheat fertility when promotion of homologous pairing and synapsis by TaZIP4-B2 is preserved.

scholarly journals A separation-of-function ZIP4 wheat mutant allows crossover between related chromosomes and is meiotically stable

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Azahara C. Martín ◽  
Abdul Kader Alabdullah ◽  
Graham Moore
Keyword(s):  
Wheat Breeding ◽  
Wild Type ◽  
Grain Number ◽  
Homologous Chromosomes ◽  
Chromosome 5B ◽  
Correct Pairing ◽  
New Gene ◽  
Multiple Genomes ◽  
Mutant Lines ◽  
Homoeologous Chromosomes

AbstractMany species, including most flowering plants, are polyploid, possessing multiple genomes. During polyploidisation, fertility is preserved via the evolution of mechanisms to control the behaviour of these multiple genomes during meiosis. On the polyploidisation of wheat, the major meiotic gene ZIP4 duplicated and diverged, with the resulting new gene TaZIP4-B2 being inserted into chromosome 5B. Previous studies showed that this TaZIP4-B2 promotes pairing and synapsis between wheat homologous chromosomes, whilst suppressing crossover between related (homoeologous) chromosomes. Moreover, in wheat, the presence of TaZIP4-B2 preserves up to 50% of grain number. The present study exploits a ‘separation-of-function’ wheat Tazip4-B2 mutant named zip4-ph1d, in which the Tazip4-B2 copy still promotes correct pairing and synapsis between homologues (resulting in the same pollen profile and fertility normally found in wild type wheat), but which also allows crossover between the related chromosomes in wheat haploids of this mutant. This suggests an improved utility for the new zip4-ph1d mutant line during wheat breeding, compared to the previously described CRISPR Tazip4-B2 and ph1 mutant lines. The results also reveal that loss of suppression of homoeologous crossover between wheat chromosomes does not in itself reduce wheat fertility when promotion of homologous pairing and synapsis by TaZIP4-B2 is preserved.

Assessment of the roles of SPO11-2 and SPO11-4 in meiosis in rice using CRISPR/Cas9 mutagenesis

2020 ◽  
Vol 71 (22) ◽  
pp. 7046-7058 ◽  
Author(s):  
Ian Fayos ◽  
Anne Cécile Meunier ◽  
Aurore Vernet ◽  
Sergi Navarro-Sanz ◽  
Murielle Portefaix ◽  
...  
Keyword(s):  
Double Strand Breaks ◽  
Wild Type ◽  
Strand Breaks ◽  
Homologous Chromosomes ◽  
Pollen Mother Cells ◽  
In The Wild ◽  
Bivalent Formation ◽  
Biallelic Mutations ◽  
Mother Cells ◽  
Mutant Lines

Abstract In Arabidopsis, chromosomal double-strand breaks at meiosis are presumably catalyzed by two distinct SPO11 transesterases, AtSPO11-1 and AtSPO11-2, together with M-TOPVIB. To clarify the roles of the SPO11 paralogs in rice, we used CRISPR/Cas9 mutagenesis to produce null biallelic mutants in OsSPO11-1, OsSPO11-2, and OsSPO11-4. Similar to Osspo11-1, biallelic mutations in the first exon of OsSPO11-2 led to complete panicle sterility. Conversely, all Osspo11-4 biallelic mutants were fertile. To generate segregating Osspo11-2 mutant lines, we developed a strategy based on dual intron targeting. Similar to Osspo11-1, the pollen mother cells of Osspo11-2 progeny plants showed an absence of bivalent formation at metaphase I, aberrant segregation of homologous chromosomes, and formation of non-viable tetrads. In contrast, the chromosome behavior in Osspo11-4 male meiocytes was indistinguishable from that in the wild type. While similar numbers of OsDMC1 foci were revealed by immunostaining in wild-type and Osspo11-4 prophase pollen mother cells (114 and 101, respectively), a surprisingly high number (85) of foci was observed in the sterile Osspo11-2 mutant, indicative of a divergent function between OsSPO11-1 and OsSPO11-2. This study demonstrates that whereas OsSPO11-1 and OsSPO11-2 are the likely orthologs of AtSPO11-1 and AtSPO11-2, OsSPO11-4 has no major role in wild-type rice meiosis.

The Genetic Control of Chromosome Pairing in Wheat

1990 ◽  
Vol 17 (3) ◽  
pp. 239 ◽  
Author(s):  
LH Ji ◽  
P Langridge
Keyword(s):  
Molecular Biology ◽  
Genetic Control ◽  
Mechanism Of Action ◽  
Chromosome Pairing ◽  
Genetic Information ◽  
Chromosome Pair ◽  
Homologous Chromosomes ◽  
Chromosome 5B ◽  
Cytogenetic Studies ◽  
Homoeologous Chromosomes

Bread wheat is an allohexaploid with three pairs of homoeologous chromosomes. This means that each chromosome pair is present in three related but not truly homologous chromosomes. In order to maintain the integrity of the three chromosome sets, pairing must be very tightly controlled at meiosis to allow homologous but not homoeologous chromosomes to pair and recombine. Several genes (termed Ph genes) are known to be involved in controlling chromosome pairing in wheat, but the strongest effect has been associated with a gene on the long arm of chromosome 5B, Phl. The manipulation of this gene can be used to induce recombination between chromosomes that will not normally pair at meiosis. This has application in the introduction of new genetic information into wheat. Elucidation of the mechanism of action of the Ph genes has centred around genetic and cytogenetic studies with little attempt to investigate the molecular biology or biochemistry of these genes. Isolation of genes in meiosis in yeast and genes associated with the aerly stages of meiosis in lily have provided a potential entry point into the identification of the analogous genes in wheat.

scholarly journals A Duplicated Copy of the Meiotic Gene ZIP4 Preserves up to 50% Pollen Viability and Grain Number in Polyploid Wheat

Biology ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 290
Author(s):  
Abdul Kader Alabdullah ◽  
Graham Moore ◽  
Azahara C. Martín
Keyword(s):  
Pollen Viability ◽  
Pollen Grains ◽  
Wheat Chromosome ◽  
Grain Number ◽  
Meiotic Gene ◽  
Chromosome 5B ◽  
Mutant Pollen ◽  
Female Gametogenesis ◽  
Chromosome 3B

Although most flowering plants are polyploid, little is known of how the meiotic process evolves after polyploidisation to stabilise and preserve fertility. On wheat polyploidisation, the major meiotic gene ZIP4 on chromosome 3B duplicated onto 5B and diverged (TaZIP4-B2). TaZIP4-B2 was recently shown to promote homologous pairing, synapsis and crossover, and suppress homoeologous crossover. We therefore suspected that these meiotic stabilising effects could be important for preserving wheat fertility. A CRISPR Tazip4-B2 mutant was exploited to assess the contribution of the 5B duplicated ZIP4 copy in maintaining pollen viability and grain setting. Analysis demonstrated abnormalities in 56% of meiocytes in the Tazip4-B2 mutant, with micronuclei in 50% of tetrads, reduced size in 48% of pollen grains and a near 50% reduction in grain number. Further studies showed that most of the reduced grain number occurred when Tazip4-B2 mutant plants were pollinated with the less viable Tazip4-B2 mutant pollen rather than with wild type pollen, suggesting that the stabilising effect of TaZIP4-B2 on meiosis has a greater consequence in subsequent male, rather than female gametogenesis. These studies reveal the extraordinary value of the wheat chromosome 5B TaZIP4-B2 duplication to agriculture and human nutrition. Future studies should further investigate the role of TaZIP4-B2 on female fertility and assess whether different TaZIP4-B2 alleles exhibit variable effects on meiotic stabilisation and/or resistance to temperature change.

scholarly journals Trans-splicing as a Novel Mechanism to Explain Interallelic Complementation in Drosophila

Genetics ◽  
2002 ◽  
Vol 160 (4) ◽  
pp. 1481-1487 ◽  
Author(s):  
Fabien Mongelard ◽  
Mariano Labrador ◽  
Ellen M Baxter ◽  
Tatiana I Gerasimova ◽  
Victor G Corces
Keyword(s):  
Molecular Characterization ◽  
Wild Type ◽  
Functional Protein ◽  
Gypsy Insulator ◽  
Type Function ◽  
Homologous Chromosomes ◽  
Trans Splicing ◽  
Interallelic Complementation

AbstractTwo mutant alleles of the same gene, each located in one of the two homologous chromosomes, may in some instances restore the wild-type function of the gene. This is the case with certain combinations of mutant alleles in the mod(mdg4) gene. This gene encodes several different proteins, including Mod(mdg4)2.2, a component of the gypsy insulator. This protein is encoded by two separate transcription units that can be combined in a trans-splicing reaction to form the mature Mod(mdg4)2.2-encoding RNA. Molecular characterization of complementing alleles shows that they affect the two different transcription units. Flies homozygous for each allele are missing the Mod(mdg4)2.2 protein, whereas wild-type trans-heterozygotes are able to synthesize almost normal levels of the Mod(mdg4)2.2 product. This protein is functional as judged by its ability to form a functional insulator complex. The results suggest that the interallelic complementation in the mod(mdg4) gene is a consequence of trans-splicing between two different mutant transcripts. A conclusion from this observation is that the trans-splicing reaction that takes place between transcripts produced on two different mutant chromosomes ensures wild-type levels of functional protein.

scholarly journals The Arabidopsis HOP2 Gene Has a Role in Preventing illegitimate Exchanges between Nonhomologous Chromosomes

2021 ◽  
Author(s):  
YIsell Farahani-Tafreshi ◽  
Chun Wei ◽  
Peilu Gan ◽  
Jenya Daradur ◽  
C. Daniel Riggs ◽  
...  
Keyword(s):  
Active Role ◽  
Crossing Over ◽  
Wild Type ◽  
Positive Role ◽  
Homologous Chromosomes ◽  
Chromosome Synapsis ◽  
Radiation Induced ◽  
Nonhomologous Chromosome ◽  
Chromosome Exchanges

Meiotic homologous chromosomes pair up and undergo crossing over. In many eukaryotes both intimate pairing and crossing over require the induction of double stranded breaks (DSBs) and subsequent repair via Homologous Recombination (HR). In these organisms, two key proteins are the recombinases RAD51 and DMC1. Recombinase-modulators HOP2 and MND1 have been identified as proteins that assist RAD51 and DMC1 and are needed to promote stabilized pairing. We have probed the nature of the genetic lesions seen in hop2 mutants and looked at the role of HOP2 in the fidelity of genetic exchanges. Using γH2AX as a marker for unrepaired DSBs we found that hop2-1 and mnd1 mutants have different appearance/disappearance for DSBs than wild type, but all DSBs are repaired by mid-late pachytene. Therefore, the bridges and fragments seen from metaphase I onward are due to mis-repaired DSBs, not unrepaired ones. Studying Arabidopsis haploid meiocytes we found that wild type haploids produced the expected five univalents, but hop2-1 haploids suffered many illegitimate exchanges that were stable enough to produce bridged chromosomes during segregation. Our results suggest that HOP2 has a significant active role in preventing nonhomologous associations. We also found evidence that HOP2 plays a role in preventing illegitimate exchanges during repair of radiation-induced DSBs in rapidly dividing petal cells. Thus, HOP2 plays both a positive role in promoting homologous chromosome synapsis and a separable role in preventing nonhomologous chromosome exchanges. Possible mechanisms for this second important role are discussed.

scholarly journals Alpha Carbonic Anhydrase 5 Mediates Stimulation of ATP Synthesis by Bicarbonate in Isolated Arabidopsis Thylakoids

2021 ◽  
Vol 12 ◽  
Author(s):  
Tatiana P. Fedorchuk ◽  
Inga A. Kireeva ◽  
Vera K. Opanasenko ◽  
Vasily V. Terentyev ◽  
Natalia N. Rudenko ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Arabidopsis Thaliana ◽  
Carbonic Anhydrase ◽  
Atp Synthesis ◽  
Thylakoid Membranes ◽  
Wild Type ◽  
Gene Encoding ◽  
Mutant Lines ◽  
Stimulation Of ◽  
Soluble Carbonic Anhydrase

We studied bicarbonate-induced stimulation of photophosphorylation in thylakoids isolated from leaves of Arabidopsis thaliana plants. This stimulation was not observed in thylakoids of wild-type in the presence of mafenide, a soluble carbonic anhydrase inhibitor, and was absent in thylakoids of two mutant lines lacking the gene encoding alpha carbonic anhydrase 5 (αCA5). Using mass spectrometry, we revealed the presence of αCA5 in stromal thylakoid membranes of wild-type plants. A possible mechanism of the photophosphorylation stimulation by bicarbonate that involves αCA5 is proposed.

scholarly journals Genetic analysis of the Arabidopsis TIR1/AFB auxin receptors reveals both overlapping and specialized functions

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Michael J Prigge ◽  
Matthieu Platre ◽  
Nikita Kadakia ◽  
Yi Zhang ◽  
Kathleen Greenham ◽  
...  
Keyword(s):  
Genetic Analysis ◽  
Early Embryo ◽  
Wild Type ◽  
The Family ◽  
Dependent Inhibition ◽  
Root Gravitropism ◽  
Specialized Function ◽  
Mutant Lines

The TIR1/AFB auxin co-receptors mediate diverse responses to the plant hormone auxin. The Arabidopsis genome encodes six TIR1/AFB proteins representing three of the four clades that were established prior to angiosperm radiation. To determine the role of these proteins in plant development we performed an extensive genetic analysis involving the generation and characterization of all possible multiply-mutant lines. We find that loss of all six TIR1/AFB proteins results in early embryo defects and eventually seed abortion, and yet a single wild-type allele of TIR1 or AFB2 is sufficient to support growth throughout development. Our analysis reveals extensive functional overlap between even the most distantly related TIR1/AFB genes except for AFB1. Surprisingly, AFB1 has a specialized function in rapid auxin-dependent inhibition of root growth and early phase of root gravitropism. This activity may be related to a difference in subcellular localization compared to the other members of the family.

scholarly journals Mutagenesis development of actinoplanes sp. KCTC 9161 by N-methyl-N'-nitro-N-nitrosoguanidine (NTG) and screening for acarbose production

2018 ◽  
Vol 14 (4) ◽  
pp. 753-760
Author(s):  
Do Thi Tuyen ◽  
Nguyen The Duong ◽  
Le Thanh Hoang
Keyword(s):  
Type Ii Diabetes ◽  
Wild Type Strain ◽  
Fermentation Medium ◽  
Original Strain ◽  
Wild Type ◽  
Chromatography Method ◽  
Mutant Strains ◽  
Insulin Dependent ◽  
Mutant Lines ◽  
Layer Chromatography

Acarbose has been widely used in the therapy of type II diabetes (non-insulin dependent) because it controls blood sugar contents of patients after meals. Acarbose, a pseudo-oligosaccharide, acts as a competitive -glucosidase inhibitor. Acarbose is produced by the strains of Bacillus, Streptomyces and Actinoplanes sp. The aim of this study was to develop mutagenesis for an Actinoplanes sp. strain and screening for acarbose production. The spores of Actinoplanes sp. KCTC 9161 strain were subjected to be mutated by N-methyl-N'-nitro-N-nitrosoguanidine (NTG) for screening and finding mutant strains that were capable of production of higher acarbose (an inhibitor of α-glucosidase) higher than wild type strain. Firstly, the original NTG solution was prepared in phosphate buffer 0.05 M, pH 6.9 and the safety concentration of NTG was determined at 5 mg/ml. Then, the spores were incubated with different NTG amounts and duration. The living colonies were transferred to fermentation medium. The results obtained showed that 15 mutant strains were produced higher acarbose than wild type when used thin layer chromatography method for analysis and comparing with standard acarbose (Sigma). Three cell lines among total tested 15 mutant lines of Actinoplanes sp. KCTC 9161 produced acarbose at a higher level or indicated a higher inhibitory activity toward α-glucosidase than the original strain. Enzymatic inhibitory ativity of α-glucosidase of three mutant strains (Actinoplanes sp. KCTC- L4, L11, L14) was increased 1.3 fold higher than wild type and Actinoplanes sp. KCTC spores were very sensitive to NTG toxic, 98% spores could not survive at the treatment condition of 50 µg NTG for 30 minutes. In addition, an applicable protocol for mutating Actinoplanes sp. using NTG was suggested for further research.

Multiple effects of the starch synthase II mutation in developing wheat endosperm

2007 ◽  
Vol 34 (5) ◽  
pp. 431 ◽  
Author(s):  
Behjat Kosar-Hashemi ◽  
Zhongyi Li ◽  
Oscar Larroque ◽  
Ahmed Regina ◽  
Makoto Yamamori ◽  
...  
Keyword(s):  
Triticum Aestivum L ◽  
Endosperm Development ◽  
Starch Synthase ◽  
Starch Granules ◽  
Branching Enzyme ◽  
Wild Type ◽  
Drastic Reduction ◽  
Branching Patterns ◽  
Soluble Phase ◽  
Mutant Lines

A line of wheat (Triticum aestivum L.), sgp-1, that does not express starch synthase II (SSII, also known as SGP-1) has previously been reported. In this study, F1 derived doubled haploid lines with homozygous wild type or mutant alleles for SGP-1 genes were identified from a cross between the original mutant and a wild type Australian cultivar. Analysis of the starch granules showed that in the mutant lines they are markedly distorted from 15 days postanthesis during grain development. Starch branching patterns showed an increase in the proportion of short chains (DP 6–10) at an earlier stage, but this increase became much more pronounced at 15 days postanthesis and persisted until maturity. There was also a consistent and drastic reduction throughout seed development in the relative amounts of starch branching enzyme II (SBEII, comprising SBEIIa and SBEIIb) and starch synthase I (SSI) bound to the starch granules. In the soluble phase, however, there was relatively little change in the amount of SBEIIb, SBEIIa or SSI protein. Therefore loss of SSII specifically leads to the loss of SBEIIb, SBEIIa and SSI protein in the granule-bound phase and the effect of this mutation is clearly manifest from the mid-stage of endosperm development in wheat.

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