Tello Javier, Torres-Pérez Rafael, Grimplet Jérôme, Carbonell-Bejerano Pablo, Martínez-Zapater José Miguel, Ibáñez Javier
Instituto de Ciencias de la Vid y del Vino (CSIC, Universidad de La Rioja, Gobierno de La Rioja), Carretera LO-20 salida 13, Finca La Grajera, 26007, Logroño, Spain.
BMC Plant Biol. 2015 Oct 23;15:253. doi: 10.1186/s12870-015-0622-2.
Domestication and selection of Vitis vinifera L. for table and wine grapes has led to a large level of berry size diversity in current grapevine cultivars. Identifying the genetic basis for this natural variation is paramount both for breeding programs and for elucidating which genes contributed to crop evolution during domestication and selection processes. The gene VvNAC26, which encodes a NAC domain-containing transcription factor, has been related to the early development of grapevine flowers and berries. It was selected as candidate gene for an association study to elucidate its possible participation in the natural variation of reproductive traits in cultivated grapevine.
A grapevine collection of 114 varieties was characterized during three consecutive seasons for different berry and bunch traits. The promoter and coding regions of VvNAC26 gene (VIT_01s0026g02710) were sequenced in all the varieties of the collection, and the existing polymorphisms (SNP and INDEL) were detected. The corresponding haplotypes were inferred and used for a phylogenetic analysis. The possible associations between genotypic and phenotypic data were analyzed independently for each season data, using different models and significance thresholds.
A total of 30 non-rare polymorphisms were detected in the VvNAC26 sequence, and 26 different haplotypes were inferred. Phylogenetic analysis revealed their clustering in two major haplogroups with marked phenotypic differences in berry size between varieties harboring haplogroup-specific alleles. After correcting the statistical models for the effect of the population genetic stratification, we found a set of polymorphisms associated with berry size explaining between 8.4 and 21.7% (R(2)) of trait variance, including those generating the differentiation between both haplogroups. Haplotypes built from only three polymorphisms (minihaplotypes) were also associated with this trait (R(2): 17.5 - 26.6%), supporting the involvement of this gene in the natural variation for berry size.
Our results suggest the participation of VvNAC26 in the determination of the grape berry final size. Different VvNAC26 polymorphisms and their combination showed to be associated with different features of the fruit. The phylogenetic relationships between the VvNAC26 haplotypes and the association results indicate that this nucleotide variation may have contributed to the differentiation between table and wine grapes.
对酿酒葡萄进行鲜食葡萄和酿酒葡萄的驯化与选育，使得当前葡萄品种的浆果大小存在很大差异。确定这种自然变异的遗传基础对于育种计划以及阐明在驯化和选育过程中哪些基因促成了作物进化至关重要。编码含NAC结构域转录因子的VvNAC26基因与葡萄花和浆果的早期发育有关。它被选为关联研究的候选基因，以阐明其可能参与栽培葡萄生殖性状自然变异的情况。
在连续三个季节对114个葡萄品种的群体进行不同浆果和果穗性状的表征。对该群体所有品种的VvNAC26基因（VIT_01s0026g02710）的启动子和编码区进行测序，并检测现有的多态性（单核苷酸多态性和插入缺失）。推断相应的单倍型并用于系统发育分析。使用不同模型和显著性阈值，针对每个季节的数据独立分析基因型和表型数据之间可能的关联。
在VvNAC26序列中总共检测到30个非罕见多态性，并推断出26种不同的单倍型。系统发育分析表明它们聚为两个主要单倍群，携带单倍群特异性等位基因的品种之间在浆果大小上存在明显的表型差异。在对群体遗传分层效应的统计模型进行校正后，我们发现一组与浆果大小相关的多态性，解释了性状变异的8.4%至21.7%（R²），包括那些导致两个单倍群分化的多态性。仅由三个多态性构建的单倍型（微型单倍型）也与该性状相关（R²：17.5 - 26.6%），支持该基因参与浆果大小的自然变异。
我们的结果表明VvNAC26参与了葡萄浆果最终大小的决定。不同的VvNAC26多态性及其组合与果实的不同特征相关。VvNAC26单倍型之间的系统发育关系和关联结果表明，这种核苷酸变异可能促成了鲜食葡萄和酿酒葡萄之间的分化。
