Auger Donald L, Gray Anjali Dogra, Ream Thomas S, Kato Akio, Coe Edward H, Birchler James A
Division of Biological Sciences, University of Missouri, Columbia, Missouri 65211, USA.
Genetics. 2005 Jan;169(1):389-97. doi: 10.1534/genetics.104.032987. Epub 2004 Oct 16.
The molecular basis of hybrid vigor (heterosis) has remained unknown despite the importance of this phenomenon in evolution and in practical breeding programs. To formulate a molecular basis of heterosis, an understanding of gene expression in inbred and hybrid states is needed. In this study, we examined the amount of various transcripts in hybrid and inbred individuals (B73 and Mo17) to determine whether the quantities of specific messenger RNAs were additive or nonadditive in the hybrids. Further, we examined the levels of the same transcripts in hybrid triploid individuals that had received unequal genomic contributions, one haploid genome from one parent and two from the other. If allelic expression were merely the additive value in hybrids from the two parents, the midparent values would be observed. Our study revealed that a substantial number of genes do not exhibit the midparent value of expression in hybrids. Instead, transcript levels in the diploid hybrids correlate negatively with the levels in diploid inbreds. Although transcript levels were clearly nonadditive, transcript levels in triploid hybrids were affected by genomic dosage.
尽管杂种优势（杂种活力）这一现象在进化和实际育种计划中具有重要意义，但其分子基础仍不清楚。为了阐明杂种优势的分子基础，需要了解近交和杂交状态下的基因表达情况。在本研究中，我们检测了杂交个体和近交个体（B73和Mo17）中各种转录本的数量，以确定杂种中特定信使RNA的数量是相加的还是非相加的。此外，我们还检测了杂交三倍体个体中相同转录本的水平，这些个体接受了不等的基因组贡献，一个亲本提供一个单倍体基因组，另一个亲本提供两个单倍体基因组。如果等位基因表达仅仅是两个亲本杂种中的相加值，那么就会观察到中亲值。我们的研究表明，大量基因在杂种中并不表现出中亲表达值。相反，二倍体杂种中的转录本水平与二倍体近交系中的水平呈负相关。尽管转录本水平明显是非相加的，但三倍体杂种中的转录本水平受基因组剂量的影响。
