Zhou Leina, Zhu Can, Fang Xiaojian, Liu Hangqin, Zhong Shuyang, Li Yan, Liu Jiacheng, Song Yang, Jian Xing, Lin Zhongwei
National Maize Improvement Center, Center for Crop Functional Genomics and Molecular Breeding, Joint Laboratory for International Cooperation in Crop Molecular Breeding, Ministry of Education, Beijing Key Laboratory of Crop Genetic Improvement, Laboratory of Crop Heterosis and Utilization, China Agricultural University, Beijing 100193, China.
National Maize Improvement Center, Center for Crop Functional Genomics and Molecular Breeding, Joint Laboratory for International Cooperation in Crop Molecular Breeding, Ministry of Education, Beijing Key Laboratory of Crop Genetic Improvement, Laboratory of Crop Heterosis and Utilization, China Agricultural University, Beijing 100193, China.
Mol Plant. 2021 Nov 1;14(11):1831-1845. doi: 10.1016/j.molp.2021.07.005. Epub 2021 Jul 14.
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 of awn loss in sorghum during domestication or improvement remains unknown. Here, we identified the awn1 gene encoding a transcription factor with the ALOG domain that is responsible for awn loss during sorghum domestication or improvement. awn1 arose from a gene duplication on chromosome 10 that translocated to chromosome 3, recruiting a new promoter from the neighboring intergenic region filled with "noncoding DNA" and recreating the first exon and intron. awn1 acquired high expression after duplication and represses the elongation of awns in domesticated sorghum. Comparative mapping revealed high collinearity at the awn1 paralog locus on chromosome 10 across cereals, and awn growth and development were successfully reactivated on the rice spikelet by inactivating the rice awn1 ortholog. RNA-seq and DAP-seq revealed that as a transcriptional repressor, AWN1 bound directly to a motif in the regulatory regions of three MADS genes related to flower development and two genes, DL and LKS2, involved in awn development. AWN1 downregulates the expression of these genes, thereby repressing awn elongation. The preexistence of regulatory elements in the neighboring intergenic region of awn1 before domestication implicates that noncoding DNA may serve as a treasure trove for evolution during sorghum adaptation to a changing world. Taken together, our results suggest that gene duplication can rapidly drive the evolution of gene regulatory networks in plants.
包括高粱在内的一些谷类作物的芒缺失，是谷类作物驯化或改良过程中的一个关键转变，这一转变促进了谷物的收获与储存。高粱在驯化或改良过程中芒缺失的遗传基础尚不清楚。在此，我们鉴定出了芒1（awn1）基因，该基因编码一个具有ALOG结构域的转录因子，它导致了高粱在驯化或改良过程中芒的缺失。awn1起源于10号染色体上的一个基因复制事件，该复制基因易位到3号染色体，从邻近充满“非编码DNA”的基因间区域招募了一个新的启动子，并重新构建了第一个外显子和内含子。awn1在复制后获得了高表达，并抑制了驯化高粱中芒的伸长。比较图谱分析显示，谷类作物10号染色体上awn1旁系同源基因座具有高度共线性，通过使水稻awn1直系同源基因失活，成功地在水稻小穗上重新激活了芒的生长与发育。RNA测序（RNA-seq）和DNA亲和纯化测序（DAP-seq）显示，作为转录抑制因子，AWN1直接结合到与花发育相关的3个MADS基因以及与芒发育相关的2个基因（DL和LKS2）调控区域中的一个基序上。AWN1下调这些基因的表达，从而抑制芒的伸长。驯化前awn1邻近基因间区域调控元件的存在表明，非编码DNA可能是高粱适应不断变化的世界过程中进化的宝库。综上所述，我们的研究结果表明基因复制可以快速推动植物基因调控网络的进化。
