Boyce Thompson Institute for Plant Research, Ithaca, New York, 14853, USA.
Boyce Thompson Institute for Plant Research, Ithaca, New York, 14853, USA
J Exp Bot. 2015 Feb;66(2):571-8. doi: 10.1093/jxb/eru379. Epub 2014 Sep 23.
Plants show considerable within-species variation in their resistance to insect herbivores. In the case of Zea mays (cultivated maize), Rhopalosiphum maidis (corn leaf aphids) produce approximately twenty times more progeny on inbred line B73 than on inbred line Mo17. Genetic mapping of this difference in maize aphid resistance identified quantitative trait loci (QTL) on chromosomes 4 and 6, with the Mo17 allele reducing aphid reproduction in each case. The chromosome 4 QTL mapping interval includes several genes involved in the biosynthesis of DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one), a maize defensive metabolite that also is required for callose accumulation in response to aphid feeding. Consistent with the known association of callose with plant defence against aphids, R. maidis reproduction on B73×Mo17 recombinant inbred lines was negatively correlated with both DIMBOA content and callose formation. Further genetic mapping, as well as experiments with near-isogenic lines, confirmed that the Mo17 allele causes increased DIMBOA accumulation relative to the B73 allele. The chromosome 6 aphid resistance QTL functions independently of DIMBOA accumulation and has an effect that is additive to that of the chromosome 4 QTL. Thus, at least two separate defence mechanisms account for the higher level of R. maidis resistance in Mo17 compared with B73.
植物在其对昆虫食草动物的抗性方面表现出相当大的种内变异性。以玉米（栽培玉米）为例，玉米蚜虫（玉米叶蝉）在自交系 B73 上产生的后代大约比在自交系 Mo17 上产生的后代多 20 倍。玉米蚜虫抗性的这种差异的遗传图谱定位确定了染色体 4 和 6 上的数量性状基因座（QTL），Mo17 等位基因在每种情况下都降低了蚜虫的繁殖。染色体 4 QTL 图谱区间包含几个参与 DIMBOA（2,4-二羟基-7-甲氧基-1,4-苯并恶嗪-3-酮）生物合成的基因，玉米防御代谢物，也需要对蚜虫取食做出反应的几丁质积累。与已知的几丁质与植物对蚜虫的防御有关一致，B73×Mo17 重组自交系上 R. maidis 的繁殖与 DIMBOA 含量和几丁质形成呈负相关。进一步的遗传图谱以及与近等基因系的实验证实，Mo17 等位基因导致 DIMBOA 积累相对于 B73 等位基因增加。染色体 6 上的蚜虫抗性 QTL 独立于 DIMBOA 积累起作用，并且其作用与染色体 4 QTL 的作用相加。因此，与 B73 相比，Mo17 中至少有两种独立的防御机制导致 R. maidis 抗性水平更高。
