Aguiar Bruno, Vieira Jorge, Cunha Ana E, Fonseca Nuno A, Iezzoni Amy, van Nocker Steve, Vieira Cristina P
Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal; Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Porto, Portugal.
CRACS-INESC Porto, Rua do Campo Alegre 1021/1055, 4169-007, Porto, Portugal; European Bioinformatics Institute (EMBL-EBI), Welcome Trust Genome Campus, CB10 1SD, Cambridge, United Kingdom.
PLoS One. 2015 May 19;10(5):e0126138. doi: 10.1371/journal.pone.0126138. eCollection 2015.
S-RNase-based gametophytic self-incompatibility (GSI) has evolved once before the split of the Asteridae and Rosidae. This conclusion is based on the phylogenetic history of the S-RNase that determines pistil specificity. In Rosaceae, molecular characterizations of Prunus species, and species from the tribe Pyreae (i.e., Malus, Pyrus, Sorbus) revealed different numbers of genes determining S-pollen specificity. In Prunus only one pistil and pollen gene determine GSI, while in Pyreae there is one pistil but multiple pollen genes, implying different specificity recognition mechanisms. It is thus conceivable that within Rosaceae the genes involved in GSI in the two lineages are not orthologous but possibly paralogous. To address this hypothesis we characterised the S-RNase lineage and S-pollen lineage genes present in the genomes of five Rosaceae species from three genera: M. × domestica (apple, self-incompatible (SI); tribe Pyreae), P. persica (peach, self-compatible (SC); Amygdaleae), P. mume (mei, SI; Amygdaleae), Fragaria vesca (strawberry, SC; Potentilleae), and F. nipponica (mori-ichigo, SI; Potentilleae). Phylogenetic analyses revealed that the Malus and Prunus S-RNase and S-pollen genes belong to distinct gene lineages, and that only Prunus S-RNase and SFB-lineage genes are present in Fragaria. Thus, S-RNase based GSI system of Malus evolved independently from the ancestral system of Rosaceae. Using expression patterns based on RNA-seq data, the ancestral S-RNase lineage gene is inferred to be expressed in pistils only, while the ancestral S-pollen lineage gene is inferred to be expressed in tissues other than pollen.
基于S-核酸酶的配子体自交不亲和性（GSI）在菊亚纲和蔷薇亚纲分化之前就已经进化出现过一次。这一结论是基于决定雌蕊特异性的S-核酸酶的系统发育史得出的。在蔷薇科中，李属物种以及梨亚族（即苹果属、梨属、花楸属）物种的分子特征表明，决定S-花粉特异性的基因数量不同。在李属中，只有一个雌蕊基因和一个花粉基因决定GSI，而在梨亚族中，有一个雌蕊基因但有多个花粉基因，这意味着存在不同的特异性识别机制。因此，可以推测在蔷薇科中，这两个谱系中参与GSI的基因并非直系同源，而可能是旁系同源。为了验证这一假设，我们对来自三个属的五个蔷薇科物种基因组中存在的S-核酸酶谱系基因和S-花粉谱系基因进行了特征分析，这五个物种分别是：苹果（苹果，自交不亲和（SI）；梨亚族）、桃（桃，自交亲和（SC）；桃亚族）、梅（梅，SI；桃亚族）、野草莓（草莓，SC；委陵菜族）和日本草莓（森草莓，SI；委陵菜族）。系统发育分析表明，苹果属和李属的S-核酸酶基因和S-花粉基因属于不同的基因谱系，并且草莓属中仅存在李属的S-核酸酶基因和SFB谱系基因。因此，苹果基于S-核酸酶的GSI系统是从蔷薇科的祖先系统独立进化而来的。根据RNA测序数据的表达模式推断，祖先S-核酸酶谱系基因仅在雌蕊中表达，而祖先S-花粉谱系基因则在除花粉之外的其他组织中表达。
