基因差异表达与杂种优势形成机制探讨

Mechanism on differential gene expression and heterosis formation

对杂种优势这一普遍而重要的生物学现象研究虽有百余年的历史,但其根本机理尚未阐述清楚。继基因组组成差异及基因效应研究之后,基因表达差异成为探寻杂种优势分子机理新的切入点。旨在通过揭示杂种中等位基因差异表达、杂种与亲本间基因差异表达的调控机制,来认识杂种优势形成的分子机理,从而达到指导育种实践的目的。文章概述了杂种等位基因差异表达现象及其产生机理,总结了杂种与亲本相比所呈现出的加性、显性和超显性等多种差异基因表达模式,归纳了表达谱研究筛选出的与杂种优势形成有关的基因,以及某些关键生化代谢途径对杂种优势形成的贡献。但由于杂种优势机理的复杂性,基因表达研究并没有得出统一的表达模式,大多数杂种优势基因也不能被归属为同一类别。尽管如此,基因表达谱研究毕竟迈出了解析杂种优势形成复杂基因表达网络的第一步,随着表达谱技术和生物信息学的不断更新和发展,杂种优势形成的分子机理有望在基因表达层面上取得突破。

Despite the rediscovery ofheterosis about a century ago and the suggestion of various genetic models to ex- plain this phenomenon, little consensus has yet been reached about the genetic basis of heterosis. Following the genome organization variation and gene effects, an understanding of gene differential expression in hybrids and its parents provides a new opportunity to speculate on mechanisms that might lead to heterosis. Investigation on allele-specific gene expression in hybrid and gene differential expression between hybrids and its parents might contribute to improve our understanding of the molecular basis of heterosis and eventually guide breeding practices. In this review, we discussed the recent researches on allelic-specific expression in hybrid which was frequently observed in recent studies and analyzed its regulatory mecha- nism. All possible modes of gene action, including additivity, high- and low-parent dominance, underdominance, and over- dominance, were observed when investigating gene differential expression between hybrids and its parents. Data from tran- scriptomic studies screened several heterosis-associated genes and highlighted the importance of certain key biochemical pathways that may prove to be quintessential for the manifestation of heterosis. So far, no uniform global expression pat- terns were observed in these gene expression studies. Most heterosis-associated gene expression analyses have not revealed a predominant functional category to which differentially expressed genes belong. However, these gene expression profiling studies represent a first step towards the definition of the complex gene expression networks that might be relevant in the context of heterosis. New technique on gene expression profile and advancements in bioinformatics will facilitate our un- derstanding of the genetic basis of heterosis at the gene-expression level.