Natural GMOs Part 305. Domestication of millet made possible by movement of mobile DNA

Loss of seed shattering occurred during domestication of the crop foxtail millet. Turns out it happened by natural DNA engineering with a mobile DNA (transposon):

Summary

Loss of seed shattering was a key step during cereal domestication, and greatly facilitated seed harvest of the staple cereal foxtail millet (Setaria italica) because the cereal has very small seeds. However, the genetic basis for this loss has been largely unknown. Here we combined comparative and association mapping to identify an 855-bp Harbinger transposable element insertion in the second exon of the foxtail millet gene shattering1 (sh1) that was responsible for loss of seed shattering. The sh1 gene encodes zinc finger and YABBY domains. The insert prevents transcription of the second exon, causing partial loss of the zinc finger domain and then loss of natural seed shattering. Specifically, sh1 functions as a transcription repressor and represses the transcription of genes associated with lignin synthesis in the abscission zone, including CAD2. The diversity of sh1 is highly reduced in foxtail millet, consistent with either a severe domestication bottleneck and/or a selective sweep. Phylogenetic analysis of sh1 further revealed a single origin of foxtail millet in China. Our results support the theories that transposons were the most active factors in genome evolution driving loss of natural seed shattering during foxtail millet domestication and that sh1 underwent parallel selection during domestication across different cereal species.

A transposon insertion drove the loss of natural seed shattering during foxtail millet domestication
Hangqin Liu, Xiaojian Fang, Leina Zhou, Yan Li, Can Zhu, Jiacheng Liu, Yang Song, Xing Jian, Min Xu, Li Dong…

Molecular Biology and Evolution, msac078, https://doi.org/10.1093/molbev/msac078
Published:
07 April 2022