Molecular characterization of berry skin color reversion on grape somatic variants

Abstract

BACKGROUND: During grapevine domestication somatic variation has been used as a source of diversity for clonal selection. OBJECTIVE: This work provides additional information on the molecular mechanisms responsible for berry skin color reversion on a subset of somatic variants for berry skin color never investigated before. METHODS: The berry color locus and its surrounding genomic region were genetically characterized through a layer-specific approach, which has already been proven to be a successful method to decipher the molecular mechanisms responsible for color reversions on somatic variants. RESULTS: Deletions of different extent and positions were detected among less-pigmented/unpigmented variants derived from a pigmented wild-type. These deletions affected only the inner cell layer in the less pigmented variants and both cell layers in the unpigmented variants. Regarding the pigmented variants derived from an unpigmented wild-type, only one group was distinguished by the Gret1 retrotransposon partial excision from the VvMybA1 promoter. Moreover, within this latter group, VvMybA2 showed an important role regarding the phenotypic variation, through the recovery of the functional G allele. CONCLUSIONS: This investigation focused on the berry color locus using somatic variants for berry skin color, promotes a better understanding of the evolutionary events behind their origin and variability, opening an opportunity for their use in the genetic improvement of varieties.

Genetic analysis of a white-to-red berry skin color reversion and its transcriptomic and metabolic consequences in grapevine (Vitis vinifera cv. ‘Moscatel Galego’)

“…To further investigate the genetic structure of the berry color locus and its surrounding genomic region, 12 molecular markers were screened, 10 SSRs spread throughout this region of chromosome 2 and two R2R3-MYB genes, VvMYBA1 and VvMYBA2 , which were analyzed regarding their functional and non-functional allelic configurations (Table 1). This investigation was performed by using a well-established layer-specific approach, which has already been proven to be a successful method to decipher the molecular mechanisms responsible for color reversions on other grape somatic variants [15, 16, 30].…”

Berry color variation in grapevine as a source of diversity

“…The clonal polymorphism affecting berry skin color is the most wellstudied polymorphism leading to various phenotypes, having been intensively investigated in different grapevine varieties (Ferreira et al, 2018(Ferreira et al, , 2016Giannetto et al, 2008;Migliaro et al, 2014).…”

“…This resulted from the simultaneous occurrence of mutations in MYBA1 and MYBA2 genes, which cause the loss of transcription factor expression and, consequently, abrogate anthocyanin biosynthesis. Different combinatorial mutations on these two genes led to the emergence of not only the white-skinned phenotypes, but also to a range of pale-phenotypes, largely assessed in different genotypes and somatic variants (Ferreira et al, 2018(Ferreira et al, , 2017Lijavetzky et al, 2006;Migliaro et al, 2014). These were selected during the domestication process, favoring a rapid diffusion of the less colored phenotypes, leading to the diversification of berry color.…”

“…'Ruby Okuyama', which may have occurred as a result of intra-recombination between the 5′LTR and 3′LTR of Gret1 in the 5′-flanking region near the coding region of MYBA1, and its functional allele (Kobayashi et al, 2005(Kobayashi et al, , 2004. Since then it has been identified in several red-skinned somatic variants derived from white-skinned cultivars, and described as the main mechanism responsible for color recovery on white-skinned cultivars (Ferreira et al, 2018;Migliaro et al, 2014).…”

Genetics and expression of anthocyanin pathway genes in the major skin-pigmented Portuguese cultivar ‘Vinhão’ developing berries

“…MYBA2 gene is inactivated by two non-conservative mutations: i) SNP at position VvMYBA2R44 (or K980) in the coding sequence (T instead of G) that leads to an amino acid substitution (change of arginine at in the red allele to leucine in the white allele), rendering non-function; ii) frame shift resulting in a smaller protein (dinucleotide deletion altering the reading frame at the amino acid position 258) (Walker et al, 2007). Moreover, the altered pigmentation of berries' skin can be affected by different mutation patterns on the skin cell layers of the shoot apical meristem (Ferreira et al, 2018;Migliaro et al, 2017;Vezzulli et al, 2012).…”