scholarly journals The Molecular Evolution of terminal ear1, a Regulatory Gene in the Genus Zea

Genetics ◽  
1999 ◽  
Vol 153 (3) ◽  
pp. 1455-1462 ◽  
Author(s):  
Shawn E White ◽  
John F Doebley

Abstract Nucleotide diversity in the terminal ear1 (te1) gene, a regulatory locus hypothesized to be involved in the morphological evolution of maize (Zea mays ssp. mays), was investigated for evidence of past selection. Nucleotide polymorphism in a 1.4-kb region of te1 was analyzed for a sample of 26 sequences isolated from 12 maize lines, five populations of the maize progenitor, Z. mays ssp. parviglumis, six other Zea populations, and two Tripsacum species. Although nucleotide diversity in te1 in maize is reduced relative to ssp. parviglumis, phylogenetic and statistical analyses of the pattern of polymorphism among these sequences provided no evidence of past selection, indicating that the region of the gene studied was probably not involved in maize evolution. The level of reduction in genetic diversity in te1 in maize relative to its progenitor is comparable to that found in previous reports for isozymes and other neutrally evolving maize genes and is consistent with a genome-wide reduction of genetic diversity resulting from a domestication bottleneck. An estimate of the age (1.2–1.4 million yr) of the maize gene pool based on te1 is roughly consistent with previous estimates based on other neutral genes, but may be biased by the apparently slow synonymous substitution rate at te1.


Genetics ◽  
2000 ◽  
Vol 156 (1) ◽  
pp. 257-268 ◽  
Author(s):  
Peter Andolfatto ◽  
Molly Przeworski

Abstract We analyze nucleotide polymorphism data for a large number of loci in areas of normal to high recombination in Drosophila melanogaster and D. simulans (24 and 16 loci, respectively). We find a genome-wide, systematic departure from the neutral expectation for a panmictic population at equilibrium in natural populations of both species. The distribution of sequence-based estimates of 2Nc across loci is inconsistent with the assumptions of the standard neutral theory, given the observed levels of nucleotide diversity and accepted values for recombination and mutation rates. Under these assumptions, most estimates of 2Nc are severalfold too low; in other words, both species exhibit greater intralocus linkage disequilibrium than expected. Variation in recombination or mutation rates is not sufficient to account for the excess of linkage disequilibrium. While an equilibrium island model does not seem to account for the data, more complicated forms of population structure may. A proper test of alternative demographic models will require loci to be sampled in a more consistent fashion.



2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Teame Gereziher MEHARI ◽  
Yanchao XU ◽  
Richard Odongo MAGWANGA ◽  
Muhammad Jawad UMER ◽  
Joy Nyangasi KIRUNGU ◽  
...  

Abstract Background Cotton is an important commercial crop for being a valuable source of natural fiber. Its production has undergone a sharp decline because of abiotic stresses, etc. Drought is one of the major abiotic stress causing significant yield losses in cotton. However, plants have evolved self-defense mechanisms to cope abiotic factors like drought, salt, cold, etc. The evolution of stress responsive transcription factors such as the trihelix, a nodule-inception-like protein (NLP), and the late embryogenesis abundant proteins have shown positive response in the resistance improvement to several abiotic stresses. Results Genome wide identification and characterization of the effects of Light-Harvesting Chloro a/b binding (LHC) genes were carried out in cotton under drought stress conditions. A hundred and nine proteins encoded by the LHC genes were found in the cotton genome, with 55, 27, and 27 genes found to be distributed in Gossypium hirsutum, G. arboreum, and G. raimondii, respectively. The proteins encoded by the genes were unevenly distributed on various chromosomes. The Ka/Ks (Non-synonymous substitution rate/Synonymous substitution rate) values were less than one, an indication of negative selection of the gene family. Differential expressions of genes showed that majority of the genes are being highly upregulated in the roots as compared with leaves and stem tissues. Most genes were found to be highly expressed in MR-85, a relative drought tolerant germplasm. Conclusion The results provide proofs of the possible role of the LHC genes in improving drought stress tolerance, and can be explored by cotton breeders in releasing a more drought tolerant cotton varieties.



2019 ◽  
Vol 19 (1) ◽  
Author(s):  
Xintong Liu ◽  
Dandan Li ◽  
Shiya Zhang ◽  
Yaling Xu ◽  
Zhao Zhang

Abstract Background The WRKYs are a major family of plant transcription factors that play roles in the responses to biotic and abiotic stresses; however, a comprehensive study of the WRKY family in roses (Rosa sp.) has not previously been performed. Results In the present study, we performed a genome-wide analysis of the WRKY genes in the rose (Rosa chinensis), including their phylogenetic relationships, gene structure, chromosomal locations, and collinearity. Using a phylogenetic analysis, we divided the 56 RcWRKY genes into three subgroups. The RcWRKYs were unevenly distributed across all seven rose chromosomes, and a study of their collinearity suggested that genome duplication may have played a major role in RcWRKY gene duplication. A Ka/Ks analysis indicated that they mainly underwent purifying selection. Botrytis cinerea infection induced the expression of 19 RcWRKYs, most of which had undergone gene duplication during evolution. These RcWRKYs may regulate rose resistance against B. cinerea. Based on our phylogenetic and expression analyses, RcWRKY41 was identified as a candidate regulatory gene in the response to B. cinerea infection, which was confirmed using virus-induced gene silencing. Conclusions This study provides useful information to facilitate the further study of the function of the rose WRKY gene family.



Stroke ◽  
2020 ◽  
Vol 51 (8) ◽  
pp. 2454-2463
Author(s):  
Keith L. Keene ◽  
Hyacinth I. Hyacinth ◽  
Joshua C. Bis ◽  
Steven J. Kittner ◽  
Braxton D. Mitchell ◽  
...  

Background and Purpose: Stroke is a complex disease with multiple genetic and environmental risk factors. Blacks endure a nearly 2-fold greater risk of stroke and are 2× to 3× more likely to die from stroke than European Americans. Methods: The COMPASS (Consortium of Minority Population Genome-Wide Association Studies of Stroke) has conducted a genome-wide association meta-analysis of stroke in >22 000 individuals of African ancestry (3734 cases, 18 317 controls) from 13 cohorts. Results: In meta-analyses, we identified one single nucleotide polymorphism (rs55931441) near the HNF1A gene that reached genome-wide significance ( P =4.62×10 −8 ) and an additional 29 variants with suggestive evidence of association ( P <1×10 −6 ), representing 24 unique loci. For validation, a look-up analysis for a 100 kb region flanking the COMPASS single nucleotide polymorphism was performed in SiGN (Stroke Genetics Network) Europeans, SiGN Hispanics, and METASTROKE (Europeans). Using a stringent Bonferroni correction P value of 2.08×10 −3 (0.05/24 unique loci), we were able to validate associations at the HNF1A locus in both SiGN ( P =8.18×10 −4 ) and METASTROKE ( P =1.72×10 −3 ) European populations. Overall, 16 of 24 loci showed evidence for validation across multiple populations. Previous studies have reported associations between variants in the HNF1A gene and lipids, C-reactive protein, and risk of coronary artery disease and stroke. Suggestive associations with variants in the SFXN4 and TMEM108 genes represent potential novel ischemic stroke loci. Conclusions: These findings represent the most thorough investigation of genetic determinants of stroke in individuals of African descent, to date.







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