To optimize fitness, plants must efficiently allocate their resources between growth and defense. Although phytohormone crosstalk has emerged as a major player in balancing growth and defense, the genetic basis by which plants manage this balance remains elusive. We previously identified a quantitative disease-resistance locus, qRfg2, in maize (Zea mays) that protects against the fungal disease Gibberella stalk rot. Here, through map-based cloning, we demonstrate that the causal gene at qRfg2 is ZmAuxRP1, which encodes a plastid stroma-localized auxin-regulated protein. ZmAuxRP1 responded quickly to pathogen challenge with a rapid yet transient reduction in expression that led to arrested root growth but enhanced resistance to Gibberella stalk rot and Fusarium ear rot. ZmAuxRP1 was shown to promote the biosynthesis of indole-3-acetic acid (IAA), while suppressing the formation of benzoxazinoid defense compounds. ZmAuxRP1 presumably acts as a resource regulator modulating indole-3-glycerol phosphate and/or indole flux at the branch point between the IAA and benzoxazinoid biosynthetic pathways. The concerted interplay between IAA and benzoxazinoids can regulate the growth–defense balance in a timely and efficient manner to optimize plant fitness.

为了优化适应性，植物必须在生长和防御之间有效地分配资源。尽管植物激素的串扰已成为平衡生长和防御的主要因素，但植物管理这种平衡的遗传基础仍然难以捉摸。我们先前在玉米（Zea mays）中鉴定了一个定量的抗病基因座qRfg2，可以预防真菌病赤霉菌茎腐病。在这里，通过基于图的克隆，我们证明qRfg 2处的因果基因是ZmAuxRP1，它编码质体基质定位的生长素调节蛋白。ZmAuxRP1迅速而短暂的表达减少迅速响应病原体挑战，导致根系生长受阻，但对赤霉菌茎腐病和镰刀菌耳腐病的抵抗力增强。ZmAuxRP1已显示出可以促进吲哚-3-乙酸（IAA）的生物合成，同时抑制了苯并恶嗪类防御化合物的形成。ZmAuxRP1可能在IAA和苯并恶嗪类生物合成途径之间的分支点上充当调节吲哚-3-甘油磷酸酯和/或吲哚通量的资源调节剂。IAA和苯并恶嗪类化合物之间的协调相互作用可以及时有效地调节植物的生长防御平衡，从而优化植物的适应性。