Vitis vinifera cultivar:Corinto Bianco and Pedro Ximenez Transcriptome or Gene expression

Seedlessness is a highly relevant trait in grapevine berries that are intended for fresh consumption or raisin production. Corinto Bianco (CB) is a parthenocarpic somatic variant of the seeded cultivar Pedro Ximenes (PX). Both variants were compared to understand the basis of this parthenocarpic phenotype. Macrogametogenesis was aborted in CB, which was also pollen sterile. Occasionally, one seed developed in 1.6% of CB berries that displayed a comparable size to that of PX berries. Microsatellite genotyping and flow cytometry analyses of seedlings generated from these seeds identified tetraploid plants recapitulating the same genotype than the mother plant and triploids likely resulting from fertilization of diploid cells by external pollen, uncovering that most CB viable gametes were unreduced gametes. Microarray and RNA-seq analyses identified 1,958 genes differentially expressed between CB and PX developing flowers. CB-upregulated and downregulated genes were enriched in sporophyte and gametophyte-preferential genes, respectively and indicated a lack of postmeiotic germline development in CB flowers. RNA-seq was also useful to identify SNP polymorphisms distinguishing both variants and parthenocarpy-responsible candidate genes including a putative deleterious substitution in the protein encoded by a HAL2-like gene.

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Royo C, Carbonell-Bejerano P, Torres-Pérez R, Nebish A, Martínez Ó, Rey M, Aroutiounian R, Ibáñez J, Martínez-Zapater JM