Trucillo Silva Ignacio, Abbaraju Hari Kishan R, Fallis Lynne P, Liu Hongjun, Lee Michael, Dhugga Kanwarpal S
Department of Agronomy, Iowa State University, Ames, IA, 50011, USA.
Trait Discovery and Technology, DuPont Pioneer, Johnston, IA, 50131, USA.
Theor Appl Genet. 2017 Jul;130(7):1453-1466. doi: 10.1007/s00122-017-2900-x. Epub 2017 Apr 25.
Aside from the identification of 32 QTL for N metabolism in the seedling leaves of a maize testcross population, alanine aminotransferase was found to be a central enzyme in N assimilation. Excessive application of nitrogen (N) fertilizer to grow commercial crops like maize is a cause of concern because of the runoff of excess N into streams and rivers. Breeding maize with improved N use efficiency (NUE) would reduce environmental pollution as well as input costs for the farmers. An understanding of the genetics underlying N metabolism is key to breeding for NUE. From a set of 176 testcrosses derived from the maize IBMsyn10 population grown in hydroponics, we analyzed the youngest fully expanded leaf at four-leaf stage for enzymes and metabolites related to N metabolism. Three enzymes, along with one metabolite explained 24% of the variation in shoot dry mass. Alanine aminotransferase (AlaAT) stood out as the key enzyme in maintaining the cellular level of glutamate as it alone explained 58% of the variation in this amino acid. Linkage mapping revealed 32 quantitative trait loci (QTL), all trans to the genomic positions of the structural genes for various enzymes of N assimilation. The QTL models for different traits accounted for 7-31% of the genetic variance, whereas epistasis was generally not significant. Five coding regions underlying 1-LOD QTL confidence intervals were identified for further validation studies. Our results provide evidence for the key role of AlaAT in N assimilation likely through homeostatic control of glutamate levels in the leaf cells. The two QTL identified for this enzyme would help to select desirable recombinants for improved N assimilation.
除了在一个玉米测交群体的幼苗叶片中鉴定出32个与氮代谢相关的数量性状基因座（QTL）外，还发现丙氨酸转氨酶是氮同化过程中的核心酶。过量施用氮肥来种植玉米等经济作物令人担忧，因为过量的氮会流入溪流和河流。培育具有更高氮利用效率（NUE）的玉米将减少环境污染以及农民的投入成本。了解氮代谢的遗传学基础是培育氮高效利用品种的关键。从水培条件下种植的玉米IBMsyn10群体衍生出的176个测交组合中，我们分析了四叶期最幼嫩的完全展开叶片中与氮代谢相关的酶和代谢物。三种酶和一种代谢物解释了地上部干质量变异的24%。丙氨酸转氨酶（AlaAT）作为维持细胞内谷氨酸水平的关键酶脱颖而出，因为仅它就解释了这种氨基酸变异的58%。连锁图谱分析揭示了32个数量性状基因座（QTL），均与氮同化各种酶的结构基因的基因组位置呈反式关系。不同性状的QTL模型解释了7%-31%的遗传变异，而上位性通常不显著。确定了1-LOD QTL置信区间内的五个编码区用于进一步的验证研究。我们的结果为AlaAT在氮同化中可能通过对叶细胞中谷氨酸水平的稳态控制发挥关键作用提供了证据。为该酶鉴定出的两个QTL将有助于选择理想的重组体以改善氮同化。
