Monsalvo Ivan, Parasecolo Leonardo, Pullano Sarah, Lin Jie, Shahabi Aida, Ly Melissa, Kwon Hyejung, Mathur Khushi, Rodrillo Karl Angelo M, Ifa Demian R, Kovinich Nik
Department of Biology, Faculty of Science, York University, 4700 Keele St., Toronto, ON M3J 1P3, Canada.
Department of Chemistry, Faculty of Science, York University, 4700 Keele St., Toronto, ON M3J 1P3, Canada.
Int J Mol Sci. 2025 Apr 13;26(8):3683. doi: 10.3390/ijms26083683.
Phytoalexins are specialized metabolites that are synthesized by plants in response to pathogens. A paradigm in transcription factor (TF) biology is that conserved TFs have dedicated roles across plant lineages in regulating specific branches of specialized metabolism. However, the Arabidopsis () NAC family TF ANAC042 (a.k.a. JUNGBRUNNEN1 or JUB1) regulates the synthesis of camalexin, a Trp-derived phytoalexin specifically produced by several species, whereas its homolog in soybean () regulates the synthesis of glyceollins, which are Phe-derived phytoalexins specific to soybean. The question addressed by this research is whether ANAC042 broadly regulates phytoalexin biosynthetic pathways in Arabidopsis. Using a novel matrix-assisted laser desorption ionization high-resolution mass spectrometry (MALDI-HRMS) method, we found that the Arabidopsis loss-of-function mutant elicited with bacterial flagellin (Flg22) is deficient in lineage-specific Trp- and conserved Phe-derived phytoalexins-namely camalexin and 4-hydroxyindole-3-carbonyl nitrile (4OH-ICN), and pathogen-inducible monolignols and scopoletin, respectively. Overexpressing in the mutant restored or exceeded wildtype amounts of the metabolites. The expression of phytoalexin biosynthetic genes in mutant and overexpression lines mirrored the accumulation of metabolites. Yeast-one hybrid and promoter-reporter assays in found that the ANAC042 protein directly binds and activates the promoters of , , and genes for the synthesis of camalexin, 4OH-ICN, and pathogen-inducible monolignol/scopoletin, respectively. Our results demonstrate that ANAC042 regulates conserved and lineage-specific phytoalexin pathways in Arabidopsis. The latter suggests that it is an opportunistic TF that has coopted lineage-specific genes into phytoalexin metabolism, thus providing an exception to the current paradigm.
植物抗毒素是植物在响应病原体时合成的特殊代谢产物。转录因子（TF）生物学中的一个范例是，保守的转录因子在整个植物谱系中具有专门的作用，以调节特殊代谢的特定分支。然而，拟南芥NAC家族转录因子ANAC042（又名JUNGBRUNNEN1或JUB1）调节camalexin的合成，camalexin是一种由色氨酸衍生的植物抗毒素，由几种拟南芥属植物特异性产生，而其在大豆中的同源物则调节大豆素的合成，大豆素是大豆特有的由苯丙氨酸衍生的植物抗毒素。本研究探讨的问题是ANAC042是否广泛调节拟南芥中植物抗毒素的生物合成途径。使用一种新型的基质辅助激光解吸电离高分辨率质谱（MALDI-HRMS）方法，我们发现用细菌鞭毛蛋白（Flg22）诱导的拟南芥功能丧失突变体缺乏谱系特异性色氨酸衍生和保守的苯丙氨酸衍生的植物抗毒素，即camalexin和4-羟基吲哚-3-羰基腈（4OH-ICN），以及病原体诱导的单木质素和东莨菪素。在突变体中过表达ANAC042可恢复或超过野生型代谢物的量。突变体和过表达系中植物抗毒素生物合成基因的表达反映了代谢物的积累。在拟南芥中进行的酵母单杂交和启动子报告分析发现，ANAC042蛋白分别直接结合并激活用于合成camalexin、4OH-ICN和病原体诱导的单木质素/东莨菪素的基因的启动子。我们的结果表明，ANAC042调节拟南芥中保守的和谱系特异性的植物抗毒素途径。后者表明它是一种机会主义转录因子，已将谱系特异性基因纳入植物抗毒素代谢，从而为当前范例提供了一个例外。
