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J Exp Bot. 2016 Jan;67(1):259-73. doi: 10.1093/jxb/erv452. Epub 2015 Oct 9.

Developmental, transcriptome, and genetic alterations associated with parthenocarpy in the grapevine seedless somatic variant Corinto bianco.

Author information

1
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.
2
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.
3
Department of Genetics and Cytology, Yerevan State University, 1 Alex Manoogian str., 0025 Yerevan, Armenia.
4
Departamento de Biología Vegetal y Ciencia del Suelo. Facultad de Biología. Universidad de Vigo, 36310 Vigo, Spain.

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.

KEYWORDS:

Diplospory; RNA-seq; SNP; Vitis vinifera.; embryo sac; gametogenesis; grapevine; meiosis; microarray; parthenocarpy; pollen sterility; polyploidy; seedlessness; somatic variation; transcriptomics; unreduced gamete

PMID:
26454283
DOI:
10.1093/jxb/erv452
[Indexed for MEDLINE]

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