Genomics of sorghum local adaptation to a parasitic plant
Genomics of sorghum local adaptation to a parasitic plant
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DOI：
10.1073/pnas.1908707117
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发表时间：
2020-02-25
影响因子：
11.1
通讯作者：
Lasky, Jesse R.
中科院分区：
文献类型：
--
作者：
Bellis, Emily S.;Kelly, Elizabeth A.;Lasky, Jesse R.
宿主-寄生虫协同进化可以维持物种间相互作用所涉及性状的高水平遗传多样性。在许多系统中，被寄生虫利用的宿主特征受到其他功能的限制，导致跨空间和时间的复杂选择压力。在这里，我们研究了主要作物两色高粱（Sorbicolor（L.）Moench及其与寄生杂草Striga hermonthica（Delile）Benth.的关系，这是非洲粮食安全的主要制约因素。我们假设，地理选择镶嵌跨越梯度的寄生虫发生保持遗传多样性高粱地方品种的电阻。高粱低发芽刺激剂1（LGS 1）的多个独立的功能丧失等位基因在非洲地方品种中广泛分布，并在地理上与S. hermonthica发生然而，这些等位基因在S.易患Hermonthica的区域和它们在其他地方的缺失暗示了限制它们固定的潜在权衡。LGS 1被认为通过改变独脚金内酯的立体化学引起抗性，独脚金内酯是控制植物结构和地下信号传导到真菌的激素，并且是刺激寄生虫萌发所必需的。与权衡一致，我们从分析全基因组与寄生虫分布的关联中发现了围绕LGS 1和其他候选人的平衡选择的签名。使用CRISPR-Cas9编辑的高粱的实验进一步表明，LGS 1介导的抗性的益处在很大程度上取决于寄生虫基因型和非生物环境，并以降低光系统基因表达为代价。我们的研究表明，在小农农业生态系统中，宿主抗性基因的多样性长期保持不变，为工业化农业系统和自然社区提供了有价值的比较。
Host-parasite coevolution can maintain high levels of genetic diversity in traits involved in species interactions. In many systems, host traits exploited by parasites are constrained by use in other functions, leading to complex selective pressures across space and time. Here, we study genome-wide variation in the staple crop Sorghum bicolor (L.) Moench and its association with the parasitic weed Striga hermonthica (Delile) Benth., a major constraint to food security in Africa. We hypothesize that geographic selection mosaics across gradients of parasite occurrence maintain genetic diversity in sorghum landrace resistance. Suggesting a role in local adaptation to parasite pressure, multiple independent loss-of-function alleles at sorghum LOW GERMINATION STIMULANT 1 (LGS1) are broadly distributed among African landraces and geographically associated with S. hermonthica occurrence. However, low frequency of these alleles within S. hermonthica-prone regions and their absence elsewhere implicate potential trade-offs restricting their fixation. LGS1 is thought to cause resistance by changing stereochemistry of strigolactones, hormones that control plant architecture and below-ground signaling to mycorrhizae and are required to stimulate parasite germination. Consistent with trade-offs, we find signatures of balancing selection surrounding LGS1 and other candidates from analysis of genome-wide associations with parasite distribution. Experiments with CRISPR-Cas9-edited sorghum further indicate that the benefit of LGS1-mediated resistance strongly depends on parasite genotype and abiotic environment and comes at the cost of reduced photosystem gene expression. Our study demonstrates long-term maintenance of diversity in host resistance genes across smallholder agroecosystems, providing a valuable comparison to both industrial farming systems and natural communities.