2015年11月17日，国际主流遗传学杂志《PLoS Genetics》，在线发表了华中农业大学作物遗传改良国家重点实验室玉米团队张祖新教授课题组在玉米产量性状遗传基础研究方面的研究论文“KRN4 Controls Quantitative Variation in Maize Kernel Row Number ”。刘磊博士为本文的第一作者，张祖新教授为通讯作者。张祖新教授课题组的杜艳芳、申晓蒙、李曼菲等参与了本课题研究，河北农业大学陶永生博士对本课题亦有贡献。

玉米是全球第一大农作物，2014年我国玉米年消费量为3.9亿吨左右，仅次于美国，居世界第2位（国家统计局）。同时，随着人们消费结构的不断变化，对农牧产品需求量日益增加，农牧行业饲料玉米的需求量急剧增长。同时发达国家利用玉米作为生物能源的原材料，进一步加剧了全球范围内玉米供需的紧张局势。因此提高玉米产量，应对日益严峻的粮食安全问题迫在眉睫。

玉米的单株产量可由玉米的每穗籽粒数目以及粒重共同决定，张祖新教授研究团队针对玉米的控制玉米籽粒数目的主效遗传位点KRN4，利用全基因组关联分析、图位克隆等手段，证实了KRN4位于控制玉米雌穗发育重要基因Unbranched3（UB3）基因下游60Kb，包含一个1.2Kb的转座子片段的插入缺失，为UB3的顺式调控因子，通过远距离调节UB3基因的表达量，控制玉米穗行数的数量变异。KRN4位点优良单倍型可以提高2行穗行数，增加将近20%的每穗籽粒数目，因此可以显著提升玉米产量。研究者同时发现，KRN4位点可以通过和UB3基因内的功能性SNP变异发生遗传互作，进一步提高玉米籽粒产量。现代玉米是由野生种玉米草（teosinte）驯化和改良而来，现代玉米栽培种具有较高的籽粒产量，研究者发现KRN4在玉米的驯化和改良过程中受到强烈的选择，通过对KRN4优良单倍型的强烈选择，使KRN4位点的优良单倍型频率在现代玉米中显著提高。研究者进一步利用来自两个不同玉米材料的KRN4优良单倍型，利用分子标记辅助选择的手段，成功的对两个穗行数较低的玉米自交系进行遗传改良，将它们的穗行数提高了将近18%。该研究对认识玉米产量形成的分子机理具有重要意义，同时提供了通过遗传改良提高玉米产量的重要靶点。

上述研究工作得到科技部973和国家自然科学基金等项目的资助。（来源：科学网）

KRN4 Controls Quantitative Variation in Maize Kernel Row Number

Abstract  Kernel row number (KRN) is an important component of yield during the domestication and improvement of maize and controlled by quantitative trait loci (QTL). Here, we fine-mapped a major KRN QTL, KRN4, which can enhance grain productivity by increasing KRN per ear. We found that a ~3-Kb intergenic region about 60 Kb downstream from the SBP-box gene Unbranched3 (UB3) was responsible for quantitative variation in KRN by regulating the level of UB3 expression. Within the 3-Kb region, the 1.2-Kb Presence-Absence variant was found to be strongly associated with quantitative variation in KRN in diverse maize inbred lines, and our results suggest that this 1.2-Kb transposon-containing insertion is likely responsible for increased KRN. A previously identified A/G SNP (S35, also known as Ser220Asn) in UB3 was also found to be significantly associated with KRN in our association-mapping panel. Although no visible genetic effect of S35 alone could be detected in our linkage mapping population, it was found to genetically interact with the 1.2-Kb PAV to modulate KRN. The KRN4 was under strong selection during maize domestication and the favorable allele for the 1.2-Kb PAV and S35 has been significantly enriched in modern maize improvement process. The favorable haplotype (Hap1) of 1.2-Kb-PAV-S35 was selected during temperate maize improvement, but is still rare in tropical and subtropical maize germplasm. The dissection of the KRN4 locus improves our understanding of the genetic basis of quantitative variation in complex traits in maize.

原文链接：http://www.plosgenetics.org/article/fetchObject.action?uri=info:doi/10.1371/journal.pgen.1005670&representation=PDF