Genomics of Sorghum Local Adaptation to A Parasitic Plant
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Date
2020-01
Authors
Bellisa, Emily S.
Kellya, Elizabeth A.
Lortsa, Claire M.
Gaoe, Huirong
DeLeoa, Victoria L.
Rouhanf, Germinal
Buddeng, Andrew
Bhaskarah, Govinal B.
Hui, Zhenbin
Muscarell, Robert
Journal Title
Journal ISSN
Volume Title
Publisher
PNAS
Abstract
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 tradeoffs,
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.
Description
Research Article
Keywords
Citation
Bellis, E. S., Kelly, E. A., Lorts, C. M., Gao, H., DeLeo, V. L., Rouhan, G., ... & Lasky, J. R. (2020). Genomics of sorghum local adaptation to a parasitic plant. Proceedings of the National Academy of Sciences, 117(8), 4243-4251.