title: Developmental, transcriptome, and genetic alterations associated with parthenocarpy in the grapevine seedless somatic variant Corinto bianco.
abstract: Seedlessness is a relevant trait in grapevine cultivars intended for fresh consumption or raisin production. Previous DNA marker analysis indicated that Corinto bianco (CB) is a parthenocarpic somatic variant of the seeded cultivar Pedro Ximenes (PX). This study compared both variant lines to determine the basis of this parthenocarpic phenotype. At maturity, CB seedless berries were 6-fold smaller than PX berries. The macrogametophyte was absent from CB ovules, and CB was also pollen sterile. Occasionally, one seed developed in 1.6% of CB berries. Microsatellite genotyping and flow cytometry analyses of seedlings generated from these seeds showed that most CB viable seeds were formed by fertilization of unreduced gametes generated by meiotic diplospory, a process that has not been described previously in grapevine. Microarray and RNA-sequencing analyses identified 1958 genes that were differentially expressed between CB and PX developing flowers. Genes downregulated in CB were enriched in gametophyte-preferentially expressed transcripts, indicating the absence of regular post-meiotic germline development in CB. RNA-sequencing was also used for genetic variant calling and 14 single-nucleotide polymorphisms distinguishing the CB and PX variant lines were detected. Among these, CB-specific polymorphisms were considered as candidate parthenocarpy-responsible mutations, including a putative deleterious substitution in a HAL2-like protein. Collectively, these results revealed that the absence of a mature macrogametophyte, probably due to meiosis arrest, coupled with a process of fertilization-independent fruit growth, caused parthenocarpy in CB. This study provides a number of grapevine parthenocarpy-responsible candidate genes and shows how genomic approaches can shed light on the genetic origin of woody crop somatic variants.
authors.affiliation: Instituto de Ciencias de la Vid y del Vino (Consejo Superior de Investigaciones Científicas-Universidad de La Rioja-Gobierno de La Rioja), Finca La Grajera, Carretera LO-20 - salida 13, Autovía del Camino de Santiago, 26007, Spain.
authors.forename: Carolina
authors.initials: C
authors.lastname: Royo
authors.affiliation: Instituto de Ciencias de la Vid y del Vino (Consejo Superior de Investigaciones Científicas-Universidad de La Rioja-Gobierno de La Rioja), Finca La Grajera, Carretera LO-20 - salida 13, Autovía del Camino de Santiago, 26007, Spain pablo.carbonell@icvv.es.
authors.forename: Pablo
authors.initials: P
authors.lastname: Carbonell-Bejerano
authors.affiliation: Instituto de Ciencias de la Vid y del Vino (Consejo Superior de Investigaciones Científicas-Universidad de La Rioja-Gobierno de La Rioja), Finca La Grajera, Carretera LO-20 - salida 13, Autovía del Camino de Santiago, 26007, Spain.
authors.forename: Rafael
authors.initials: R
authors.lastname: Torres-Pérez
authors.affiliation: Department of Genetics and Cytology, Yerevan State University, 1 Alex Manoogian str., 0025 Yerevan, Armenia.
authors.forename: Anna
authors.initials: A
authors.lastname: Nebish
authors.affiliation: Departamento de Biología Vegetal y Ciencia del Suelo. Facultad de Biología. Universidad de Vigo, 36310 Vigo, Spain.
authors.forename: Óscar
authors.initials: Ó
authors.lastname: Martínez
authors.affiliation: Departamento de Biología Vegetal y Ciencia del Suelo. Facultad de Biología. Universidad de Vigo, 36310 Vigo, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Rey
authors.affiliation: Department of Genetics and Cytology, Yerevan State University, 1 Alex Manoogian str., 0025 Yerevan, Armenia.
authors.forename: Rouben
authors.initials: R
authors.lastname: Aroutiounian
authors.affiliation: Instituto de Ciencias de la Vid y del Vino (Consejo Superior de Investigaciones Científicas-Universidad de La Rioja-Gobierno de La Rioja), Finca La Grajera, Carretera LO-20 - salida 13, Autovía del Camino de Santiago, 26007, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Ibáñez
authors.affiliation: Instituto de Ciencias de la Vid y del Vino (Consejo Superior de Investigaciones Científicas-Universidad de La Rioja-Gobierno de La Rioja), Finca La Grajera, Carretera LO-20 - salida 13, Autovía del Camino de Santiago, 26007, Spain.
authors.forename: José M
authors.initials: JM
authors.lastname: Martínez-Zapater
mesh_terms: D035264:Flowers / Q000235:genetics / Q000254:growth & development*; D005638:Fruit / Q000235:genetics / Q000254:growth & development*; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D012639:Seeds / Q000235:genetics / Q000254:growth & development; D017423:Sequence Analysis, RNA; D059467:Transcriptome; D027843:Vitis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism
chemical_list: D010940:Plant Proteins
keywords: Diplospory; RNA-seq; SNP; Vitis vinifera.; embryo sac; gametogenesis; grapevine; meiosis; microarray; parthenocarpy; pollen sterility; polyploidy; seedlessness; somatic variation; transcriptomics; unreduced gamete