DOE Plant Research Laboratory, Michigan State University, East Lansing, MI, 48824, USA.
Plant Resilience Institute, Michigan State University, East Lansing, MI, 48824, USA.
New Phytol. 2022 Oct;236(1):132-145. doi: 10.1111/nph.18293. Epub 2022 Jun 21.
Robust plant immunity negatively affects other fitness traits, including growth and seed production. Jasmonate (JA) confers broad-spectrum protection against plant consumers by stimulating the degradation of JASMONATE ZIM-DOMAIN (JAZ) proteins, which in turn relieves repression on transcription factors (TFs) coincident with reduced growth and fecundity. The molecular mechanisms underlying JA-mediated decreases in fitness remain largely unknown. To assess the contribution of MYC TFs to growth and reproductive fitness at high levels of defence, we mutated three MYC genes in a JAZ-deficient mutant (jazD) of Arabidopsis thaliana that exhibits strong defence and low seed yield. Genetic epistasis analysis showed that de-repression of MYC TFs in jazD not only conferred strong resistance to insect herbivory but also reduced shoot and root growth, fruit size and seed yield. We also provided evidence that the JAZ-MYC module coordinates the supply of tryptophan with the production of indole glucosinolates and the proliferation of endoplasmic reticulum bodies that metabolise glucosinolates through the action of β-glucosidases. Our results establish MYCs as major regulators of growth- and reproductive-defence trade-offs and further indicate that these factors coordinate tryptophan availability with the production of amino acid-derived defence compounds.
植物的固有免疫会对其他适应特征（包括生长和种子产量）产生负面影响。茉莉酸（JA）通过刺激 JAZ 蛋白的降解来赋予植物对消费者的广谱保护作用，进而解除对转录因子（TF）的抑制作用，同时降低生长和繁殖力。JA 介导的适应特征下降的分子机制在很大程度上仍不清楚。为了评估 MYC 转录因子在高水平防御下对生长和生殖适应特征的贡献，我们在拟南芥 jazD 突变体（表现出强烈防御和低种子产量）中突变了三个 MYC 基因。遗传上位性分析表明，MYC TF 在 jazD 中的去抑制作用不仅赋予了对昆虫取食的强抗性，还降低了地上和地下部分的生长、果实大小和种子产量。我们还提供了证据表明，JAZ-MYC 模块通过β-葡萄糖苷酶的作用协调色氨酸的供应与吲哚类芥子油苷的产生以及参与芥子油苷代谢的内质体的增殖。我们的结果确立了 MYC 作为生长和生殖防御权衡的主要调节因子，并进一步表明这些因素协调色氨酸的可用性与氨基酸衍生防御化合物的产生。
