Institute of Fruit Tree and Tea Science, National Agriculture and Food Research Organization, 2-1 Fujimoto, Tsukuba, Ibaraki, 305-8605, Japan.
Division of Apple Research, Institute of Fruit Tree and Tea Science, National Agriculture and Food Research Organization, 92-24 Nabeyashiki, Shimokuriyagawa, Morioka, Iwate, 020-0123, Japan.
Plant Mol Biol. 2024 Oct 19;114(6):113. doi: 10.1007/s11103-024-01514-0.
Although self-incompatibility in apples (Malus × domestica Borkh.) is regulated by a single S-locus with multiple S-haplotypes that comprise pistil S (S-RNase) and pollen S genes, it is not desirable in commercial orchards because it requires cross-pollination to achieve stable fruit production. Therefore, it is important to identify and characterize self-compatible apple cultivars. However, little is known about self-compatibility (SC) and its underlying molecular mechanisms in apples. In this study, we discovered that 'Vered', an early maturing and low chilling-requiring apple cultivar, exhibits stable SC, which was evaluated via self-pollination tests. The S-genotype of 'Vered' was designated as SS. Results of genetic analysis of selfed progeny of 'Vered' revealed that SC is associated with the S-haplotype, and molecular analyses indicated that it is caused by alternative splicing and a 205-bp deletion in S-RNase. These events induce frameshifts and ultimately produce the defective S-RNase isoforms that lack their C-terminal half. These results enabled us to develop a 117-bp DNA marker that can be used to assist in the selection of self-compatible apples with the dysfunctional S-RNase. Thus, analysis of 'Vered' provided insights into the molecular mechanism of the very rare trait of natural stylar-part SC. Moreover, 'Vered' is a valuable genetic resource for breeding cultivars with SC and/or low chilling requirement in apple. Our findings contribute to a better understanding of self-compatible molecular mechanisms in apple and provide for the accelerated breeding of self-compatible apple cultivars.
虽然苹果（Malus × domestica Borkh.）中的自交不亲和性由单个 S 座位上的多个 S 单倍型调控，这些 S 单倍型包括花柱 S（S-RNase）和花粉 S 基因，但在商业果园中并不理想，因为它需要异花授粉才能实现稳定的果实生产。因此，识别和表征自交亲和的苹果品种非常重要。然而，人们对苹果中的自交亲和性及其潜在的分子机制知之甚少。在本研究中，我们发现早熟且需冷量低的品种‘Vered’表现出稳定的自交亲和性，通过自花授粉试验进行评估。‘Vered’的 S 基因型被指定为 SS。对‘Vered’自交后代的遗传分析结果表明，自交亲和性与 S 单倍型相关，分子分析表明，它是由 S-RNase 的选择性剪接和 205-bp 缺失引起的。这些事件导致移码，并最终产生缺乏 C 端一半的缺陷 S-RNase 同工型。这些结果使我们能够开发出一种 117-bp 的 DNA 标记，可用于辅助选择具有功能失调 S-RNase 的自交亲和苹果。因此，对‘Vered’的分析为天然花柱部分自交亲和这一非常罕见性状的分子机制提供了见解。此外，‘Vered’是一种具有自交亲和性和/或需冷量低的苹果品种的宝贵遗传资源。我们的研究结果有助于更好地理解苹果自交亲和的分子机制，并为加速选育自交亲和苹果品种提供了依据。
