近日，国际著名杂志PLoS One在线刊登了西北农林科技大学园艺学院和澳大利亚澳洲大学的研究人员展开合作的最新研究成果“Molecular genetic features of polyploidization and aneuploidization reveal unique patterns for genome duplication in diploid Malus，”文章中，作者揭示了在苹果属植物多倍体化遗传与进化机制研究方面取得的重要进展。
西北农林科技大学园艺学院的万怡震教授和韩明玉教授为这篇文章的共同通讯作者。前者的主要研究方向为苹果品质性状基因的分子遗传定位，抗早期落叶病基因的克隆和功能，苹果砧木资源评价、利用及育种研究。韩明玉教授则主要从事果树遗传育种与栽培生理等研究。
众所周知，多倍体化是生物基因组加倍的主要方式，也是物种进化的重要途径。但是，人们对整个植物界的非整倍体化分子机制仍不十分清楚。该研究建立在大量试验数据基础上，利用细胞生物学和分子生物学手段，阐述了二倍体苹果亲本杂交后代整倍体化及非整倍化特性。研究表明，苹果二倍体杂交后代非整体个数超过整多倍体个数，说明非整倍体化可能是苹果植物基因组加倍的主要方式。研究证明所有多倍体化的配子都是遗传杂合性的，说明减数分裂中第一分裂出现异常是导致配子基因组加倍的唯一原因。
该研究首次利用分子生物学提供可靠论据表明，多倍体因其遗传上更高的杂合性而表现出更好的适应能力。本文也提供了利用共显性分子标记加速三倍体苹果育种进程的思路，提出了如何获得奇数基础染色体新物种的可能进化机制，并对苹果属植物起源进化模式进行了较大的修订和完善。文中还对非整倍体化在物种进化方面的重要性及非整倍体植物在遗传育种上的应用前景进行了系统分析与评价。该研究成果极大地有助于我们对苹果属植物进化、物种形成和适应性的理解，也为人们研究其他物种多倍体化机制提供了方法与思路。（生物谷Bioon.com）
doi:10.1371/journal.pone.0029449
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Molecular Genetic Features of Polyploidization and Aneuploidization Reveal Unique Patterns for Genome Duplication in Diploid Malus
Michael J. Considine2,3, Yizhen Wan1*, Mario F. D'Antuono3, Qian Zhou1, Mingyu Han1*, Hua Gao1, Man Wang1
Polyploidization results in genome duplication and is an important step in evolution and speciation. The Malus genome confirmed that this genus was derived through auto-polyploidization, yet the genetic and meiotic mechanisms for polyploidization, particularly for aneuploidization, are unclear in this genus or other woody perennials. In fact the contribution of aneuploidization remains poorly understood throughout Plantae. We add to this knowledge by characterization of eupolyploidization and aneuploidization in 27,542 F1 seedlings from seven diploid Malus populations using cytology and microsatellite markers. We provide the first evidence that aneuploidy exceeds eupolyploidy in the diploid crosses, suggesting aneuploidization is a leading cause of genome duplication. Gametes from diploid Malus had a unique combinational pattern; ova preserved euploidy exclusively, while spermatozoa presented both euploidy and aneuploidy. All non-reduced gametes were genetically heterozygous, indicating first-division restitution was the exclusive mode for Malus eupolyploidization and aneuploidization. Chromosome segregation pattern among aneuploids was non-uniform, however, certain chromosomes were associated for aneuploidization. This study is the first to provide molecular evidence for the contribution of heterozygous non-reduced gametes to fitness in polyploids and aneuploids. Aneuploidization can increase, while eupolyploidization may decrease genetic diversity in their newly established populations. Auto-triploidization is important for speciation in the extant Malus. The features of Malus polyploidization confer genetic stability and diversity, and present heterozygosity, heterosis and adaptability for evolutionary selection. A protocol using co-dominant markers was proposed for accelerating apple triploid breeding program. A path was postulated for evolution of numerically odd basic chromosomes. The model for Malus derivation was considerably revised. Impacts of aneuploidization on speciation and evolution, and potential applications of aneuploids and polyploids in breeding and genetics for other species were evaluated in depth. This study greatly improves our understanding of evolution, speciation, and adaptation of the Malus genus, and provides strategies to exploit polyploidization in other species.
