title: Sexual Polyploidization in Medicago sativa L.: Impact on the Phenotype, Gene Transcription, and Genome Methylation.
abstract: Polyploidization as the consequence of 2n gamete formation is a prominent mechanism in plant evolution. Studying its effects on the genome, and on genome expression, has both basic and applied interest. We crossed two diploid (2n = 2x = 16) Medicago sativa plants, a subsp. falcata seed parent, and a coerulea × falcata pollen parent that form a mixture of n and 2n eggs and pollen, respectively. Such a cross produced full-sib diploid and tetraploid (2n = 4x = 32) hybrids, the latter being the result of bilateral sexual polyploidization (BSP). These unique materials allowed us to investigate the effects of BSP, and to separate the effect of intraspecific hybridization from those of polyploidization by comparing 2x with 4x full sib progeny plants. Simple sequence repeat marker segregation demonstrated tetrasomic inheritance for all chromosomes but one, demonstrating that these neotetraploids are true autotetraploids. BSP brought about increased biomass, earlier flowering, higher seed set and weight, and larger leaves with larger cells. Microarray analyses with M. truncatula gene chips showed that several hundred genes, related to diverse metabolic functions, changed their expression level as a consequence of polyploidization. In addition, cytosine methylation increased in 2x, but not in 4x, hybrids. Our results indicate that sexual polyploidization induces significant transcriptional novelty, possibly mediated in part by DNA methylation, and phenotypic novelty that could underpin improved adaptation and reproductive success of tetraploid M. sativa with respect to its diploid progenitor. These polyploidy-induced changes may have promoted the adoption of tetraploid alfalfa in agriculture.
authors: Department of Agricultural Food and Environmental Sciences, University of Perugia, Borgo XX giugno 74, 06121, Perugia, Italy daniele.rosellini@unipg.it.
authors: Daniele
authors: 0000-0002-8473-7012
authors: D
authors: Rosellini
authors: Department of Agricultural Food and Environmental Sciences, University of Perugia, Borgo XX giugno 74, 06121, Perugia, Italy.
authors: Nicoletta
authors: N
authors: Ferradini
authors: Department of Agricultural Food and Environmental Sciences, University of Perugia, Borgo XX giugno 74, 06121, Perugia, Italy.
authors: Stefano
authors: S
authors: Allegrucci
authors: Department of Agricultural Food and Environmental Sciences, University of Perugia, Borgo XX giugno 74, 06121, Perugia, Italy.
authors: Stefano
authors: S
authors: Capomaccio
authors: Department of Biotechnology, University of Verona, Ca' Vignal 1, Strada Le Grazie 15, 37134 Verona, Italy.
authors: Elisa Debora
authors: ED
authors: Zago
authors: Institute for Sustainable Plant Protection, CNR, Via Amendola 122/D, 70126 Bari, Italy.
authors: Paola
authors: P
authors: Leonetti
authors: Istituto di Biomembrane e Bioenergetica, CNR, Via Giovanni Amendola 165/A, 70126 Bari, Italy.
authors: Bachir
authors: B
authors: Balech
authors: Department of Agriculture, University of Naples Federico II, via Università 100, 80055 Portici, Naples, Italy.
authors: Riccardo
authors: R
authors: Aversano
authors: Department of Agriculture, University of Naples Federico II, via Università 100, 80055 Portici, Naples, Italy.
authors: Domenico
authors: D
authors: Carputo
authors: Department of Agricultural Food and Environmental Sciences, University of Perugia, Borgo XX giugno 74, 06121, Perugia, Italy.
authors: Lara
authors: L
authors: Reale
authors: Department of Agricultural Food and Environmental Sciences, University of Perugia, Borgo XX giugno 74, 06121, Perugia, Italy.
authors: Fabio
authors: F
authors: Veronesi
mesh_terms: D020090:Chromosome Segregation; D032461:Chromosomes, Plant; D019175:DNA Methylation; D018506:Gene Expression Regulation, Plant; D056726:Genetic Association Studies; D018745:Genome, Plant; D006824:Hybridization, Genetic; D000455:Medicago sativa / Q000235:genetics*; D009154:Mutation; D010641:Phenotype; D011123:Polyploidy; D012098:Reproduction / Q000235:genetics*; D057891:Tetraploidy; D014158:Transcription, Genetic
keywords: DNA methylation; alfalfa; polysomic polyploids; tetrasomic inheritance; transcriptome