Dataset Information

Stepwise cis-Regulatory Changes in ZCN8 Contribute to Maize Flowering-Time Adaptation.

ABSTRACT: Maize (Zea mays ssp. mays) was domesticated in southwestern Mexico ?9,000 years ago from its wild ancestor, teosinte (Zea mays ssp. parviglumis) [1]. From its center of origin, maize experienced a rapid range expansion and spread over 90° of latitude in the Americas [2-4], which required a novel flowering-time adaptation. ZEA CENTRORADIALIS 8 (ZCN8) is the maize florigen gene and has a central role in mediating flowering [5, 6]. Here, we show that ZCN8 underlies a major quantitative trait locus (QTL) (qDTA8) for flowering time that was consistently detected in multiple maize-teosinte experimental populations. Through association analysis in a large diverse panel of maize inbred lines, we identified a SNP (SNP-1245) in the ZCN8 promoter that showed the strongest association with flowering time. SNP-1245 co-segregated with qDTA8 in maize-teosinte mapping populations. We demonstrate that SNP-1245 is associated with differential binding by the flowering activator ZmMADS1. SNP-1245 was a target of selection during early domestication, which drove the pre-existing early flowering allele to near fixation in maize. Interestingly, we detected an independent association block upstream of SNP-1245, wherein the early flowering allele that most likely originated from Zea mays ssp. mexicana introgressed into the early flowering haplotype of SNP-1245 and contributed to maize adaptation to northern high latitudes. Our study demonstrates how independent cis-regulatory variants at a gene can be selected at different evolutionary times for local adaptation, highlighting how complex cis-regulatory control mechanisms evolve. Finally, we propose a polygenic map for the pre-Columbian spread of maize throughout the Americas.

SUBMITTER: Guo L

PROVIDER: S-EPMC6537595 | biostudies-literature | 2018 Sep

REPOSITORIES: biostudies-literature

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Stepwise cis-Regulatory Changes in ZCN8 Contribute to Maize Flowering-Time Adaptation.

Guo Li L Wang Xuehan X Zhao Min M Huang Cheng C Li Cong C Li Dan D Yang Chin Jian CJ York Alessandra M AM Xue Wei W Xu Guanghui G Liang Yameng Y Chen Qiuyue Q Doebley John F JF Tian Feng F

Current biology : CB 20180913 18

Maize (Zea mays ssp. mays) was domesticated in southwestern Mexico ∼9,000 years ago from its wild ancestor, teosinte (Zea mays ssp. parviglumis) [1]. From its center of origin, maize experienced a rapid range expansion and spread over 90° of latitude in the Americas [2-4], which required a novel flowering-time adaptation. ZEA CENTRORADIALIS 8 (ZCN8) is the maize florigen gene and has a central role in mediating flowering [5, 6]. Here, we show that ZCN8 underlies a major quantitative trait locus ...[more]

PMID: 30220503

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Project description:BACKGROUND:In order to investigate the rate and limits of the response to selection from highly inbred genetic material and evaluate the respective contribution of standing variation and new mutations, we conducted a divergent selection experiment from maize inbred lines in open-field conditions during 7 years. Two maize commercial seed lots considered as inbred lines, F252 and MBS847, constituted two biological replicates of the experiment. In each replicate, we derived an Early and a Late population by selecting and selfing the earliest and the latest individuals, respectively, to produce the next generation. RESULTS:All populations, except the Early MBS847, responded to selection despite a short number of generations and a small effective population size. Part of the response can be attributed to standing genetic variation in the initial seed lot. Indeed, we identified one polymorphism initially segregating in the F252 seed lot at a candidate locus for flowering time, which explained 35% of the trait variation within the Late F252 population. However, the model that best explained our data takes into account both residual polymorphism in the initial seed lots and a constant input of heritable genetic variation by new (epi)mutations. Under this model, values of mutational heritability range from 0.013 to 0.025, and stand as an upper bound compare to what is reported in other species. CONCLUSIONS:Our study reports a long-term divergent selection experiment for a complex trait, flowering time, conducted on maize in open-field conditions. Starting from a highly inbred material, we created within a few generations populations that strikingly differ from the initial seed lot for flowering time while preserving most of the phenotypic characteristics of the initial inbred. Such material is unique for studying the dynamics of the response to selection and its determinants. In addition to the fixation of a standing beneficial mutation associated with a large phenotypic effect, a constant input of genetic variance by new mutations has likely contributed to the response. We discuss our results in the context of the evolution and mutational dynamics of populations characterized by a small effective population size.

Dataset Information

Stepwise cis-Regulatory Changes in ZCN8 Contribute to Maize Flowering-Time Adaptation.

Publications

Stepwise cis-Regulatory Changes in ZCN8 Contribute to Maize Flowering-Time Adaptation.

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