Discovery of Kernel Row Number2 that enhances grain yield and its application in maize breeding

【作者】 陈文康； Xuan Zhang； Jianghua Guo； Zhenyuan Chen； Xiangyu Zhao； Xiuyi Fu； Min Wang； Shenghui Ji； Pengfei Yin； Ning Yang； Lu Chen； Lichun Cai； Jing Xu； Lili Zhang； Yingjia Han； Yingni Xiao； Gen Xu； Yuebin Wang； Shuhui Wang； Fang Yang； David Jackson； Jinkui Cheng； Feng Qin； Feng Tian； Jianbing Yan； Jiansheng Li； 杨小红；

【Author】 Wenkang Chen;Xuan Zhang;Jianghua Guo;Zhenyuan Chen;Xiangyu Zhao;Xiuyi Fu;Min Wang;Shenghui Ji;Pengfei Yin;Ning Yang;Lu Chen;Lichun Cai;Jing Xu;Lili Zhang;Yingjia Han;Yingni Xiao;Gen Xu;Yuebin Wang;Shuhui Wang;Fang Yang;David Jackson;Jinkui Cheng;Feng Qin;Feng Tian;Jianbing Yan;Jiansheng Li;Xiaohong Yang;State Key Laboratory of Plant Environmental Resilience and National Maize Improvement Center of China, China Agricultural University;National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University;Hubei Hongshan Laboratory;Cold Spring Harbor Laboratory,Cold Spring Harbor;Center for Crop Functional Genomics and Molecular Breeding, China Agricultural University;

【机构】 State Key Laboratory of Plant Environmental Resilience and National Maize Improvement Center of China, China Agricultural University； National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University； Hubei Hongshan Laboratory； Cold Spring Harbor Laboratory,Cold Spring Harbor； Center for Crop Functional Genomics and Molecular Breeding, China Agricultural University；

【摘要】 【Objective】 Increasing maize yield per unit area plays an important role in food demands and security. As a key component of maize yield, kernel row number(KRN) has a direct effect on improving maize yield per unit area. Therefore, understanding the genetic basis of KRN and cloning the gene controlling KRN are of great significance for molecular breeding of new maize varieties with high yield. 【Method】Following a recombinantderived progeny testing strategy, we performed positional cloning of q KRN2 for KRN identified in a maize recombinant inbred line(RIL) population developed from a cross between an inbred line, B73, and an introgression line, MT-6, of which ～25% of its genome is derived from that of teosinte, the wild ancestor of maize. 【Result】We delimited qKRN2 to a 5799–base pair(bp) region that contained only one candidate gene, which we named KRN2(Kernel Row Number2). Selection in the noncoding upstream regions resulted in a reduction of KRN2 expression and an increased grain number through an increase in kernel rows. KRN2 encodes a WD40 protein and function synergistically with a gene of unknown function, DUF1644, by protein-protein interaction. Field tests show that knockout of KRN2 in maize increased grain yield by ～10%, with no apparent trade-off in other agronomic traits. To further test whether KRN2 has the same effects in the elite inbred lines and hybrids used in modern maize breeding, we used two strategies—CRISPR/Cas9-mediated gene editing and marker assisted selection(MAS)—to improve a set of maize elite inbred lines. Compared with the corresponding wild-types, most of the improved lines with null allele of KRN2 showed an increased KRN by ～0.8 to 2.1 rows. Subsequently, we developed two improved hybrids, Zhengdan958 and Nongda788, for yield testing and investigated their KRN and other agronomic traits. Remarkably, both improved Zhengdan958 and improved Nongda788 derived from crossing improved male parent and female parent could increase KRN by ～1.5 rows relative to original Zhengdan958 and Nongda788, respectively. Furthermore, the improved hybrids did not alter flowering time, plant architecture or tassel, suggesting CR-krn2 increased KRN in hybrids without apparent trade-offs in other agronomic traits. Next, we will investigate other yield-related traits to evaluate the improvement effect of KRN2 in hybrids. 【Conclusion】 In summary, we identified KRN2 that enhanced grain yield in maize and had potential application in maize breeding. These findings provide important theoretical basis and germplasm resource to breed new maize varieties with high yield.更多还原

【Abstract】 【Objective】 Increasing maize yield per unit area plays an important role in food demands and security. As a key component of maize yield, kernel row number(KRN) has a direct effect on improving maize yield per unit area. Therefore, understanding the genetic basis of KRN and cloning the gene controlling KRN are of great significance for molecular breeding of new maize varieties with high yield. 【Method】Following a recombinantderived progeny testing strategy, we performed positional cloning of q KRN2 for KRN identified in a maize recombinant inbred line(RIL) population developed from a cross between an inbred line, B73, and an introgression line, MT-6, of which ～25% of its genome is derived from that of teosinte, the wild ancestor of maize. 【Result】We delimited qKRN2 to a 5799–base pair(bp) region that contained only one candidate gene, which we named KRN2(Kernel Row Number2). Selection in the noncoding upstream regions resulted in a reduction of KRN2 expression and an increased grain number through an increase in kernel rows. KRN2 encodes a WD40 protein and function synergistically with a gene of unknown function, DUF1644, by protein-protein interaction. Field tests show that knockout of KRN2 in maize increased grain yield by ～10%, with no apparent trade-off in other agronomic traits. To further test whether KRN2 has the same effects in the elite inbred lines and hybrids used in modern maize breeding, we used two strategies—CRISPR/Cas9-mediated gene editing and marker assisted selection(MAS)—to improve a set of maize elite inbred lines. Compared with the corresponding wild-types, most of the improved lines with null allele of KRN2 showed an increased KRN by ～0.8 to 2.1 rows. Subsequently, we developed two improved hybrids, Zhengdan958 and Nongda788, for yield testing and investigated their KRN and other agronomic traits. Remarkably, both improved Zhengdan958 and improved Nongda788 derived from crossing improved male parent and female parent could increase KRN by ～1.5 rows relative to original Zhengdan958 and Nongda788, respectively. Furthermore, the improved hybrids did not alter flowering time, plant architecture or tassel, suggesting CR-krn2 increased KRN in hybrids without apparent trade-offs in other agronomic traits. Next, we will investigate other yield-related traits to evaluate the improvement effect of KRN2 in hybrids. 【Conclusion】 In summary, we identified KRN2 that enhanced grain yield in maize and had potential application in maize breeding. These findings provide important theoretical basis and germplasm resource to breed new maize varieties with high yield.更多还原