Department of Biology, Institute of Molecular Evolutionary Genetics, and Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA 16802, USA.
Curr Biol. 2011 Dec 20;21(24):2098-104. doi: 10.1016/j.cub.2011.11.011. Epub 2011 Dec 8.
Parasitism in flowering plants has evolved at least 11 times [1]. Only one family, Orobanchaceae, comprises all major nutritional types of parasites: facultative, hemiparasitic (partially photosynthetic), and holoparasitic (nonphotosynthetic) [2]. Additionally, the family includes Lindenbergia, a nonparasitic genus sister to all parasitic Orobanchaceae [3-6]. Parasitic Orobanchaceae include species with severe economic impacts: Striga (witchweed), for example, affects over 50 million hectares of crops in sub-Saharan Africa, causing more than $3 billion in damage annually [7]. Although gene losses and increased substitution rates have been characterized for parasitic plant plastid genomes [5, 8-11], the nuclear genome and transcriptome remain largely unexplored. The Parasitic Plant Genome Project (PPGP; http://ppgp.huck.psu.edu/) [2] is leveraging the natural variation in Orobanchaceae to explore the evolution and genomic consequences of parasitism in plants through a massive transcriptome and gene discovery project involving Triphysaria versicolor (facultative hemiparasite), Striga hermonthica (obligate hemiparasite), and Phelipanche aegyptiaca (Orobanche [12]; holoparasite). Here we present the first set of large-scale genomic resources for parasitic plant comparative biology. Transcriptomes of above-ground tissues reveal that, in addition to the predictable loss of photosynthesis-related gene expression in P. aegyptiaca, the nonphotosynthetic parasite retains an intact, expressed, and selectively constrained chlorophyll synthesis pathway.
开花植物中的寄生现象至少进化了 11 次[1]。只有列当科一个科，就包含了所有主要的寄生营养类型：兼性寄生（部分光合）、半寄生（部分光合）和全寄生（非光合）[2]。此外，该科还包括列当科的姊妹非寄生属 Lindenbergia[3-6]。寄生列当科包括一些对经济有严重影响的物种：Striga（独脚金），例如，它影响了撒哈拉以南非洲超过 5000 万公顷的作物，每年造成超过 30 亿美元的损失[7]。尽管寄生植物质体基因组的基因丢失和替代率增加已得到描述[5,8-11]，但其核基因组和转录组在很大程度上仍未被探索。寄生植物基因组计划（PPGP；http://ppgp.huck.psu.edu/）[2]利用列当科的自然变异，通过涉及 Triphysaria versicolor（兼性半寄生）、Striga hermonthica（专性半寄生）和 Phelipanche aegyptiaca（列当属[12]；全寄生）的大规模转录组和基因发现项目，探索植物寄生现象的进化和基因组后果。在这里，我们提出了一组寄生植物比较生物学的大规模基因组资源。地上组织的转录组表明，除了 P. aegyptiaca 中与光合作用相关的基因表达预期丢失外，这种非光合寄生虫还保留了完整、表达和选择性约束的叶绿素合成途径。
