Jasmonates are key regulators of the balance between defence and growth in plants. However, the molecular mechanisms by which activation of defence reduces growth are not yet fully understood. Here, we analyze the role of MYC transcription factors (TFs) and jasmonic acid (JA) in photomorphogenic growth. We found that multiple myc mutants share light-associated phenotypes with mutants of the phytochrome B photoreceptor, such as delayed seed germination in the dark and long hypocotyl growth. Overexpression of MYC2 in a phyB background partially suppressed its long hypocotyl phenotype. Transcriptomic analysis of multiple myc mutants confirmed that MYCs are required for full expression of red (R) light-regulated genes, including the master regulator HY5. ChIP-seq analyses revealed that MYC2 and MYC3 bind directly to the promoter of HY5 and that HY5 gene expression and protein levels are compromised in multiple myc mutants. Altogether, our results pinpoint MYCs as photomorphogenic TFs that control phytochrome responses by activating HY5 expression. This has important implications in understanding the trade-off between growth and defence as the same TFs that activate defence responses are photomorphogenic growth regulators.

中文翻译：

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JA途径MYC转录因子通过靶向HY5基因表达来调节光形态发生反应。

茉莉酸酯是植物防御与生长之间平衡的关键调节剂。但是，尚不完全了解激活防御作用降低生长的分子机制。在这里，我们分析了MYC转录因子（TFs）和茉莉酸（JA）在光形态发生生长中的作用。我们发现多个myc突变体与植物色素B光感受器的突变体具有光相关的表型，例如在黑暗和长下胚轴生长中延迟种子发芽。MYC2在phyB背景中的过表达部分抑制了其长下胚轴表型。多个myc突变体的转录组分析证实，MYC是完整表达红色（R）光调节基因（包括主调节子HY5）所必需的。ChIP-seq分析显示，MYC2和MYC3直接与HY5的启动子结合，并且在多个myc突变体中，HY5的基因表达和蛋白质水平受到损害。总而言之，我们的结果将MYC定位为通过激活HY5表达来控制植物色素反应的光形态发生TF。这对于理解生长与防御之间的权衡具有重要意义，因为激活防御反应的相同TF是光形态发生生长调节剂。