CNR - Institute of Plant Genetics - Research Division of Perugia, Via Madonna Alta 130, 06128 Perugia, Italy.
J Biotechnol. 2012 Jun 30;159(4):291-311. doi: 10.1016/j.jbiotec.2011.08.028. Epub 2011 Aug 27.
Apomixis is desirable in agriculture as a reproductive strategy for cloning plants by seeds. Because embryos derive from the parthenogenic development of apomeiotic egg cells, apomixis excludes fertilization in addition to meiotic segregation and recombination, resulting in offspring that are exact replicas of the parent. Introgression of apomixis from wild relatives to crop species and transformation of sexual genotypes into apomictically reproducing ones are long-held goals of plant breeding. In fact, it is generally accepted that the introduction of apomixis into agronomically important crops will have revolutionary implications for agriculture. This review deals with the current genetic and molecular findings that have been collected from model species to elucidate the mechanisms of apomeiosis, parthenogenesis and apomixis as a whole. Our goal is to critically determine whether biotechnology can combine key genes known to control the expression of the processes miming the main components of apomixis in plants. Two natural apomicts, as the eudicot Hypericum perforatum L. (St. John's wort) and the monocot Paspalum spp. (crowngrass), and the sexual model species Arabidopsis thaliana are ideally suited for such investigations at the genomic and biotechnological levels. Some novel views and original concepts have been faced on this review, including (i) the parallel between Y-chromosome and apomixis-bearing chromosome (e.g., comparative genomic analyses revealed common features as repression of recombination events, accumulation of transposable elements and degeneration of genes) from the most primitive (Hypericum-type) to the most advanced (Paspalum-type) in evolutionary terms, and (ii) the link between apomixis and gene-specific silencing mechanisms (i.e., likely based on chromatin remodelling factors), with merging lines of evidence regarding the role of auxin in cell fate specification of embryo sac and egg cell development in Arabidopsis. The production of engineered plants exhibiting apomictic-like phenotypes is critically reviewed and discussed.
无融合生殖在农业中很有价值，因为它可以通过种子克隆植物。由于胚胎来源于孤雌生殖的无减数分裂卵母细胞的发育，无融合生殖除了减数分裂分离和重组之外还排除了受精，从而产生与亲本完全相同的后代。将无融合生殖从野生亲缘种导入作物物种，以及将有性基因型转化为无融合生殖型，一直是植物育种的长期目标。事实上，人们普遍认为，将无融合生殖引入农业上重要的作物将对农业产生革命性的影响。本综述涉及从模式物种中收集到的当前遗传和分子发现，以阐明无减数分裂、孤雌生殖和无融合生殖的机制。我们的目标是批判性地确定生物技术是否可以将控制模拟无融合生殖主要成分过程表达的关键基因结合起来。两个天然的无融合生殖体，即双子叶植物贯叶金丝桃（Hypericum perforatum L.）（贯叶连翘）和单子叶雀稗属植物（Paspalum spp.）（皇冠草），以及有性模式物种拟南芥，非常适合在基因组和生物技术水平上进行此类研究。在这篇综述中，我们提出了一些新的观点和概念，包括：（i）从最原始的（贯叶连翘型）到最先进的（雀稗型）进化角度，Y 染色体和携带无融合生殖的染色体之间的平行关系（例如，比较基因组分析揭示了共同的特征，如重组事件的抑制、转座元件的积累和基因的退化）；（ii）无融合生殖和基因特异性沉默机制之间的联系（即可能基于染色质重塑因子），以及关于生长素在拟南芥胚囊和卵细胞发育中对细胞命运特化的作用的证据融合。本文还对具有无融合生殖样表型的工程植物的产生进行了批判性的综述和讨论。
