Gene duplication drove the loss of awn in sorghum.

Loss of the awn in some cereals including sorghum is a key transition during cereal domestication or improvement that has facilitated grain harvest and storage.The genetic basis for the loss of awn in sorghum during domestication or improvement remains unknown.Here,we identified a transcription factor gene awn1 encoding an ALOG domain,which is responsible for awn loss during sorghum domestication or improvement.awn1 arose from a gene duplication from chromosome 10 that translocated to chromosome 3,recruiting a new promoter from the neighbouring intergenic region filled with"noncoding DNA",and recreating the first exon and intron.The awn1 acquires high expr`ession after duplication and represses the elongation of awns in domesticated sorghum.Comparative mapping revealed a high collinearity at awn1 paralog locus on chromosome 10 across cereals and awn growth and development was successfully reactivated on the rice spikelet by inactivating rice awn1 orthologue.Further RNA-seq and DAP-seq revealed that as a transcription repressor,AWN1 directly bound to the motif in the regulatory regions from three MADS genes related to flower development and two genes DL and LKS2 for the development of awn,downregulated the expressions of these genes,and then repressed the elongation of awn.The preexistence of regulatory elements in the neighbouring intergenic region of awn1 before domestication signified that noncoding DNA may serve as a treasure trove for evolution during adaptation to a changing world.Our results supported that gene duplication can promptly drive the evolution of gene regulatory network.