Zinkgraf Matthew S, Meneses Nashelly, Whitham Thomas G, Allan Gerard J
Department of Biological Sciences, Environmental Genetics and Genomics Laboratory (EnGGen), Northern Arizona University, Flagstaff, AZ 86011, USA.
Department of Biological Sciences, Environmental Genetics and Genomics Laboratory (EnGGen), Northern Arizona University, Flagstaff, AZ 86011, USA.
J Insect Physiol. 2016 Jan;84:50-59. doi: 10.1016/j.jinsphys.2015.10.007. Epub 2015 Oct 27.
The identification of genes associated with ecologically important traits provides information on the potential genetic mechanisms underlying the responses of an organism to its natural environment. In this study, we investigated the genetic basis of host plant resistance to the gall-inducing aphid, Pemphigus betae, in a natural population of 154 narrowleaf cottonwoods (Populus angustifolia). We surveyed genetic variation in two genes putatively involved in sink-source relations and a phenology gene that co-located in a previously identified quantitative trait locus for resistance to galling. Using a candidate gene approach, three major findings emerged. First, natural variation in tree resistance to galling was repeatable. Sampling of the same tree genotypes 20 years after the initial survey in 1986 show that 80% of the variation in resistance was due to genetic differences among individuals. Second, we identified significant associations at the single nucleotide polymorphism and haplotype levels between the plant neutral invertase gene NIN1 and tree resistance. Invertases are a class of sucrose hydrolyzing enzymes and play an important role in plant responses to biotic stress, including the establishment of nutrient sinks. These associations with NIN1 were driven by a single nucleotide polymorphism (NIN1_664) located in the second intron of the gene and in an orthologous sequence to two known regulatory elements. Third, haplotypes from an inhibitor of invertase (C/VIF1) were significantly associated with tree resistance. The identification of genetic variation in these two genes provides a starting point to understand the possible genetic mechanisms that contribute to tree resistance to gall formation. We also build on previous work demonstrating that genetic differences in sink-source relationships of the host influence the ability of P. betae to manipulate the flow of nutrients and induce a nutrient sink.
鉴定与具有重要生态意义的性状相关的基因，可为了解生物体对自然环境响应的潜在遗传机制提供信息。在本研究中，我们调查了154株窄叶杨（Populus angustifolia）自然种群中，宿主植物对致瘿蚜虫甜菜瘿蚜（Pemphigus betae）抗性的遗传基础。我们检测了两个可能参与源库关系的基因以及一个物候基因的遗传变异，这两个基因位于先前确定的抗瘿定量性状位点上。采用候选基因法，得出了三个主要发现。第一，树木抗瘿的自然变异具有重复性。1986年首次调查20年后，对相同树木基因型进行采样，结果表明80%的抗性变异是由于个体间的遗传差异。第二，我们在植物中性转化酶基因NIN1的单核苷酸多态性和单倍型水平上，发现了与树木抗性的显著关联。转化酶是一类蔗糖水解酶，在植物对生物胁迫的响应中发挥重要作用，包括营养库的建立。与NIN1的这些关联是由位于该基因第二个内含子中的一个单核苷酸多态性（NIN1_664）驱动的，该多态性与两个已知调控元件的直系同源序列相关。第三，来自转化酶抑制剂（C/VIF1）的单倍型与树木抗性显著相关。这两个基因遗传变异的鉴定，为理解可能导致树木抗瘿形成的遗传机制提供了一个起点。我们还基于先前的研究成果，即宿主源库关系的遗传差异会影响甜菜瘿蚜操纵养分流动和诱导养分库的能力。
