广泛的基因组结构变异,如拷贝数变异(CNVs)和存在/不存在变异,是玉米显著遗传多样性的基础;然而,CNVs对玉米草食性防御的影响仍未充分开发。这里,我们报告说,玉米9-脂氧合酶基因ZmLOX5的自然复制导致秋季粘虫(FAWs)对玉米的食草抗性增加。以前,我们表明ZmLOX5衍生的氧化脂素是防御咀嚼昆虫草食动物所必需的,并鉴定了几个近交系,包括Yu796,其包含ZmLOX5的重复CNV,称为Yu796-2×LOX5。为了测试Yu796-2×LOX5基因座渗入含有单个ZmLOX5基因的草食动物易感B73背景是否是增加抗性的可行方法,我们产生了一系列近等基因系,其中包含两个,一,或通过六次回交(BC6)在B73背景中Yu796-2×LOX5基因座的零拷贝。液滴数字PCR(ddPCR)证实了Yu796-2×LOX5基因座在B73中的成功渗入。所得的B73-2×LOX5近交系对FAW的抗性增加,与ZmLOX5的表达增加相关,伤口诱导的主要羟脂素产物的产生增加,α-酮醇,9-羟基-10-氧代-12(Z),15(Z)-十八碳二烯酸(9,10-科达),下游的防御激素由这个分子调节,12-氧代-植物二烯酸(12-OPDA)和脱落酸(ABA)。令人惊讶的是,由于JA分解代谢的增加,B73-2×LOX5中伤口诱导的JA-Ile产生没有增加。此外,B73-2×LOX5显示响应干旱胁迫的失水减少,可能是由于ABA和12-OPDA含量增加。一起来看,这项研究表明,ZmLOX5的重复CNV在数量上有助于玉米抗草食动物防御,并提供了概念证明证据,表明防御基因的天然存在的重复CNV渗入到生产性但易感的作物品种中是一种可行的育种方法,可以增强植物对草食性和对非生物胁迫的耐受性。
Extensive genome structure variations, such as copy number variations (CNVs) and presence/absence variations, are the basis for the remarkable genetic diversity of maize; however, the effect of CNVs on maize herbivory defense remains largely underexplored. Here, we report that the naturally occurring duplication of the maize 9-lipoxygenase gene ZmLOX5 leads to increased resistance of maize to herbivory by fall armyworms (FAWs). Previously, we showed that ZmLOX5-derived oxylipins are required for defense against chewing insect herbivores and identified several inbred lines, including Yu796, that contained duplicated CNVs of ZmLOX5, referred to as Yu796-2×LOX5. To test whether introgression of the Yu796-2×LOX5 locus into a herbivore-susceptible B73 background that contains a single ZmLOX5 gene is a feasible approach to increase resistance, we generated a series of near-isogenic lines that contained either two, one, or zero copies of the Yu796-2×LOX5 locus in the B73 background via six backcrosses (BC6). Droplet digital PCR (ddPCR) confirmed the successful introgression of the Yu796-2×LOX5 locus in B73. The resulting B73-2×LOX5 inbred line displayed increased resistance against FAW, associated with increased expression of ZmLOX5, increased wound-induced production of its primary oxylipin product, the α-ketol, 9-hydroxy-10-oxo-12(Z),15(Z)-octadecadienoic acid (9,10-KODA), and the downstream defense hormones regulated by this molecule, 12-oxo-phytodienoic acid (12-OPDA) and abscisic acid (ABA). Surprisingly, wound-induced JA-Ile production was not increased in B73-2×LOX5, resulting from the increased JA catabolism. Furthermore, B73-2×LOX5 displayed reduced water loss in response to drought stress, likely due to increased ABA and 12-OPDA content. Taken together, this study revealed that the duplicated CNV of ZmLOX5 quantitively contributes to maize antiherbivore defense and presents proof-of-concept evidence that the introgression of naturally occurring duplicated CNVs of a defensive gene into productive but susceptible crop varieties is a feasible breeding approach for enhancing plant resistance to herbivory and tolerance to abiotic stress.