Xu Yuxing, Zhang Jingxiong, Ma Canrong, Lei Yunting, Shen Guojing, Jin Jianjun, Eaton Deren A R, Wu Jianqiang
Department of Economic Plants and Biotechnology, Yunnan Key Laboratory for Wild Plant Resources, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China.
Department of Economic Plants and Biotechnology, Yunnan Key Laboratory for Wild Plant Resources, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, China; CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing 100049, China.
Mol Plant. 2022 Aug 1;15(8):1384-1399. doi: 10.1016/j.molp.2022.07.007. Epub 2022 Jul 18.
Orobanchaceae is the largest family of parasitic plants, containing autotrophic and parasitic plants with all degrees of parasitism. This makes it by far the best family for studying the origin and evolution of plant parasitism. Here we provide three high-quality genomes of orobanchaceous plants, the autotrophic Lindenbergia luchunensis and the holoparasitic plants Phelipanche aegyptiaca and Orobanche cumana. Phylogenomic analysis of these three genomes together with those previously published and the transcriptomes of other orobanchaceous species created a robust phylogenetic framework for Orobanchaceae. We found that an ancient whole-genome duplication (WGD; about 73.48 million years ago), which occurred earlier than the origin of Orobanchaceae, might have contributed to the emergence of parasitism. However, no WGD events occurred in any lineage of orobanchaceous parasites except for Striga after divergence from their autotrophic common ancestor, suggesting that, in contrast with previous speculations, WGD is not associated with the emergence of holoparasitism. We detected evident convergent gene loss in all parasites within Orobanchaceae and between Orobanchaceae and dodder Cuscuta australis. The gene families in the orobanchaceous parasites showed a clear pattern of recent gains and expansions. The expanded gene families are enriched in functions related to the development of the haustorium, suggesting that recent gene family expansions may have facilitated the adaptation of orobanchaceous parasites to different hosts. This study illustrates a stepwise pattern in the evolution of parasitism in the orobanchaceous parasites and will facilitate future studies on parasitism and the control of parasitic plants in agriculture.
列当科是寄生植物中最大的科，包含自养植物和具有各种寄生程度的寄生植物。这使其成为目前研究植物寄生起源和进化的最佳科。在此，我们提供了三个列当科植物的高质量基因组，即自养植物绿春火焰草以及全寄生植物埃及列当和向日葵列当。对这三个基因组与先前发表的基因组以及其他列当科物种的转录组进行系统基因组分析，为列当科构建了一个强大的系统发育框架。我们发现，一次古老的全基因组复制事件（约7348万年前）早于列当科的起源，可能对寄生现象的出现起到了促进作用。然而，除了与自养共同祖先分化后的独脚金属之外，列当科寄生植物的任何谱系中都没有发生全基因组复制事件，这表明与之前的推测相反，全基因组复制与全寄生现象的出现并无关联。我们在列当科所有寄生植物内部以及列当科与菟丝子之间检测到明显的趋同基因丢失。列当科寄生植物中的基因家族呈现出近期获得和扩张的明显模式。扩张的基因家族在与吸器发育相关的功能中富集，这表明近期的基因家族扩张可能促进了列当科寄生植物对不同宿主的适应。这项研究阐明了列当科寄生植物寄生进化的逐步模式，并将促进未来关于寄生现象以及农业中寄生植物防治的研究。
