Warner R L, Hageman R H, Dudley J W, Lambert R J
Proc Natl Acad Sci U S A. 1969 Mar;62(3):785-92. doi: 10.1073/pnas.62.3.785.
Since the F(1) hybrid (B14 x Oh43) had been shown to have a higher (heterotic) level of nitrate reductase activity than either inbred parent (B14 or Oh43), studies were undertaken to determine the mode of inheritance. Standard methods for determining Mendelian inheritance were used to study segregation for level of nitrate reductase activity of individual plants. The genetic material used was the inbreds B14 and Oh43, F(1), F(1) backcrossed to both parents, F(2), F(3), and F(4) generations of the cross B14 x Oh43. The plant material was grown in the field and in growth chambers. It was shown that the maize inbreds B14 and Oh43 differ at two loci that control the level of nitrate reductase activity. Each inbred is homozygous for a dominant or partially dominant allele at one locus and homozygous recessive at a second locus. The locus at which B14 carries a dominant allele carries the recessive allele in Oh43. Oh43 has both a higher in vivo rate of synthesis of nitrate reductase and higher in vivo and in vitro loss of enzyme activity (decay) than B14. Thus, the rates of both enzyme synthesis and decay are factors governing the level of nitrate reductase activity in corn. The data suggest that the heterotic level of nitrate reductase activity in the F(1) hybrid is the result of inheritance of qualities that gives it "intermediate" rates of enzyme synthesis and decay.
由于已证明F(1)杂种(B14×Oh43)的硝酸还原酶活性水平高于任何一个自交亲本(B14或Oh43),因此开展了研究以确定其遗传模式。采用确定孟德尔遗传的标准方法来研究个体植株硝酸还原酶活性水平的分离情况。所使用的遗传材料是自交系B14和Oh43、F(1)、与双亲回交的F(1)、F(2)、F(3)以及B14×Oh43杂交组合的F(4)代。植物材料在田间和生长室中种植。结果表明,玉米自交系B14和Oh43在控制硝酸还原酶活性水平的两个位点上存在差异。每个自交系在一个位点上对于显性或部分显性等位基因是纯合的,而在第二个位点上是纯合隐性的。B14携带显性等位基因的位点在Oh43中携带隐性等位基因。Oh43的硝酸还原酶体内合成速率以及酶活性的体内和体外损失率(衰减)均高于B14。因此,酶的合成和衰减速率都是决定玉米中硝酸还原酶活性水平的因素。数据表明,F(1)杂种中硝酸还原酶活性的杂种优势水平是赋予其“中等”酶合成和衰减速率的性状遗传的结果。