Department of Plant Sciences, South Parks Road, Oxford OX1 3RB, UK.
Proc Biol Sci. 2010 Jan 7;277(1678):3-10. doi: 10.1098/rspb.2009.1209. Epub 2009 Sep 30.
Key aspects of seed development in flowering plants are held to be under epigenetic control and to have evolved as a result of conflict between the interests of the male and female gametes (kinship theory). Attempts to identify the genes involved have focused on imprinted sequences, although imprinting is only one mechanism by which male or female parental alleles may be exclusively expressed immediately post-fertilization. We have studied the expression of a subset of endosperm gene classes immediately following interploidy crosses in maize and show that departure from the normal 2 : 1 ratio between female and male genomes exerts a dramatic effect on the timing of expression of some, but not all, genes investigated. Paternal genomic excess prolongs the expression of early genes and delays accumulation of reserves, while maternal genomic excess foreshortens the expression period of early genes and dramatically brings forward endosperm maturation. Our data point to a striking interdependence between the phases of endosperm development, and are consonant with previous work from maize showing progression from cell proliferation to endoreduplication is regulated by the balance between maternal and paternal genomes, and from Arabidopsis suggesting that this 'phasing' is regulated by maternally expressed imprinted genes. Our findings are discussed in context of the kinship theory.
有观点认为，开花植物的种子发育的关键方面受表观遗传控制，并作为雄配子和雌配子利益冲突的结果（亲缘关系理论）而进化。试图鉴定涉及的基因集中在印迹序列上，尽管印迹只是一种机制，通过这种机制，雄性或雌性亲本等位基因可以在受精后立即被排他性表达。我们研究了玉米中杂种间杂交后一组胚乳基因类别的表达情况，结果表明，与正常的雌性和雄性基因组之间的 2:1 比例相比，基因组的不匹配对数对一些（而非全部）研究基因的表达时间产生了显著影响。父本基因组过剩会延长早期基因的表达时间并延迟储备物质的积累，而母本基因组过剩则会缩短早期基因的表达周期，并显著促进胚乳成熟。我们的数据表明胚乳发育的各个阶段之间存在显著的相互依存关系，与之前来自玉米的研究结果一致，该研究表明从细胞增殖到核内有丝分裂的进程受母本和父本基因组之间的平衡调控，而来自拟南芥的研究则表明这种“阶段”受母本表达的印迹基因调控。我们的发现是在亲缘关系理论的背景下讨论的。
