Is maize B chromosome preferential fertilization controlled by a single gene?

In maize, the B chromosome can undergo nondisjunction at the second pollen mitosis, producing sperm with two B chromosomes and sperm with zero B chromosomes. Preferential fertilization is the ability of the sperm carrying two B chromosomes to transmit more frequently to the embryo of a kernel than the sperm lacking the B chromosome. A translocation involving the B chromosome and chromosome 9, TB-9Sb, has been used to study preferential fertilization. The B-9 chromosome has the same properties of nondisjunction and preferential fertilization as the standard B chromosome. Deletion derivatives of B-9, which lack the centric heterochromatin and possibly some adjacent euchromatin, were tested for their ability to induce preferential fertilization. They were found to lack the capacity for preferential fertilization.

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The supernumerary B chromosome of maize: drive and genomic conflict

Open Biology ◽

10.1098/rsob.210197 ◽

2021 ◽

Vol 11 (11) ◽

Author(s):

James A. Birchler ◽

Hua Yang

Keyword(s):

Centromeric Region ◽

B Chromosome ◽

Supernumerary Chromosome ◽

Divergence Times ◽

Sperm Cells ◽

Double Fertilization ◽

Pollen Mitosis ◽

Evolutionary Time ◽

Genomic Conflict ◽

Preferential Fertilization

The supernumerary B chromosome of maize is dispensable, containing no vital genes, and thus is variable in number and presence in lines of maize. In order to be maintained in populations, it has a drive mechanism consisting of nondisjunction at the pollen mitosis that produces the two sperm cells, and then the sperm with the two B chromosomes has a preference for fertilizing the egg as opposed to the central cell in the process of double fertilization. The sequence of the B chromosome coupled with B chromosomal aberrations has localized features involved with nondisjunction and preferential fertilization, which are present at the centromeric region. The predicted genes from the sequence have paralogues dispersed across all A chromosomes and have widely different divergence times suggesting that they have transposed to the B chromosome over evolutionary time followed by degradation or have been co-opted for the selfish functions of the supernumerary chromosome.

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Sequence of the supernumerary B chromosome of maize provides insight into its drive mechanism and evolution

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2104254118 ◽

2021 ◽

Vol 118 (23) ◽

pp. e2104254118

Author(s):

Nicolas Blavet ◽

Hua Yang ◽

Handong Su ◽

Pavel Solanský ◽

Ryan N. Douglas ◽

...

Keyword(s):

Molecular Mechanisms ◽

B Chromosome ◽

Mendelian Inheritance ◽

Protein Coding ◽

Drive Mechanism ◽

Chromosome Sequence ◽

Subsequent Degradation ◽

Preferential Fertilization ◽

Second Pollen Mitosis ◽

Insight Into

B chromosomes are enigmatic elements in thousands of plant and animal genomes that persist in populations despite being nonessential. They circumvent the laws of Mendelian inheritance but the molecular mechanisms underlying this behavior remain unknown. Here we present the sequence, annotation, and analysis of the maize B chromosome providing insight into its drive mechanism. The sequence assembly reveals detailed locations of the elements involved with the cis and trans functions of its drive mechanism, consisting of nondisjunction at the second pollen mitosis and preferential fertilization of the egg by the B-containing sperm. We identified 758 protein-coding genes in 125.9 Mb of B chromosome sequence, of which at least 88 are expressed. Our results demonstrate that transposable elements in the B chromosome are shared with the standard A chromosome set but multiple lines of evidence fail to detect a syntenic genic region in the A chromosomes, suggesting a distant origin. The current gene content is a result of continuous transfer from the A chromosomal complement over an extended evolutionary time with subsequent degradation but with selection for maintenance of this nonvital chromosome.

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Linking transcription, RNA polymerase II elongation and alternative splicing

Biochemical Journal ◽

10.1042/bcj20200475 ◽

2020 ◽

Vol 477 (16) ◽

pp. 3091-3104 ◽

Cited By ~ 1

Author(s):

Luciana E. Giono ◽

Alberto R. Kornblihtt

Keyword(s):

Gene Expression ◽

Alternative Splicing ◽

Rna Polymerase Ii ◽

Environmental Changes ◽

Transcription Elongation ◽

Single Gene ◽

Regulation Of Gene Expression ◽

Regulation Of Transcription ◽

Stepping Stones ◽

Eukaryotic Transcription

Gene expression is an intricately regulated process that is at the basis of cell differentiation, the maintenance of cell identity and the cellular responses to environmental changes. Alternative splicing, the process by which multiple functionally distinct transcripts are generated from a single gene, is one of the main mechanisms that contribute to expand the coding capacity of genomes and help explain the level of complexity achieved by higher organisms. Eukaryotic transcription is subject to multiple layers of regulation both intrinsic — such as promoter structure — and dynamic, allowing the cell to respond to internal and external signals. Similarly, alternative splicing choices are affected by all of these aspects, mainly through the regulation of transcription elongation, making it a regulatory knob on a par with the regulation of gene expression levels. This review aims to recapitulate some of the history and stepping-stones that led to the paradigms held today about transcription and splicing regulation, with major focus on transcription elongation and its effect on alternative splicing.

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Strategies and clinical outcome of 250 cycles of Preimplantation Genetic Diagnosis for single gene disorders

Yearbook of Obstetrics Gynecology and Women s Health ◽

10.1016/s1090-798x(08)70132-2 ◽

2007 ◽

Vol 2007 ◽

pp. 183-184

Author(s):

L.P. Shulman

Keyword(s):

Clinical Outcome ◽

Preimplantation Genetic Diagnosis ◽

Single Gene ◽

Genetic Diagnosis ◽

Single Gene Disorders

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Genetic characterisation of children with short stature and GH or IGF1 insensitivity by single gene and whole exome sequencing

Endocrine Abstracts ◽

10.1530/endoabs.39.oc5.2 ◽

2015 ◽

Author(s):

Lucy Shapiro ◽

Martin Savage ◽

Lou Metherell ◽

Helen Storr

Keyword(s):

Short Stature ◽

Exome Sequencing ◽

Whole Exome Sequencing ◽

Single Gene ◽

Genetic Characterisation ◽

Whole Exome

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An update on HLA alleles as pharmacogenetic markers for antiepileptic drug-induced cutaneous adverse reaction

Neuroscience Research Notes ◽

10.31117/neuroscirn.v2i2.29 ◽

2019 ◽

Vol 2 (2) ◽

pp. 1-17

Author(s):

Sue-Mian Then ◽

Azman Ali Raymond

Keyword(s):

Single Gene ◽

Hypersensitivity Syndrome ◽

Allelic Frequency ◽

Stevens Johnson Syndrome ◽

Case Control Studies ◽

Drug Induced ◽

Hla Alleles ◽

Exfoliative Dermatitis ◽

Johnson Syndrome ◽

Systemic Symptoms

Epilepsy is a common neurological disorder affecting approximately 50 million people worldwide. Antiepileptic drugs (AEDs) are commonly used to treat the disease depending, mainly on the type of seizure. However, the use of AEDs may also lead to cutaneous adverse drug reactions (cADR) such as toxic epidermal necrolysis (TEN), Stevens–Johnson syndrome (SJS), exfoliative dermatitis (ED) and drug‐induced hypersensitivity syndrome/drug reaction with eosinophilia and systemic symptoms (DIHS/DRESS), which are unwanted comorbidities in epilepsy. It was first discovered that the HLA-B*15:02 allele was strongly associated with carbamazepine (CBZ)-induced SJS/TEN among Han Chinese and this led to the discovery of other HLA alleles and cytochrome P450 (CYP) genes that were significantly associated with various AED-induced cADRs across various populations. This mini review is an update on the latest findings of the involvement of various HLA alleles and CYP alleles in cADRs caused by CBZ, phenytoin (PHT), oxcarbazepine (OXC) and lamitrogine (LTG) in different case-control studies around the world. From our review, we found that CBZ- and PHT-induced cADRs were more commonly reported than the other AEDs. Therefore, there were more robust pharmacogenetics studies related to these AEDs. OXC- and LTG-induced cADRs were less commonly reported, and so more studies are needed to validate the reported association of the newer reported HLA alleles with these AEDs. It is also important to take into account the allelic frequency within a given population before drawing conclusions about the use of these alleles as genetic markers to prevent AED-induced cADR. Overall, the current body of research point to a combination of alleles as a better pharmacogenetic marker compared to the use of a single gene as a genetic marker for AED-induced cADR.

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