Indole-3-acetic acid (IAA) plays a central role in plant growth and development, and many plant-associated microbes produce IAA using tryptophan as the precursor. Using genomic analyses, we predicted that Pantoea sp. YR343, a microbe isolated from Populus deltoides, synthesizes IAA using the indole-3-pyruvate (IPA) pathway. To better understand IAA biosynthesis and the effects of IAA exposure on cell physiology, we characterized proteomes of Pantoea sp. YR343 grown in the presence of tryptophan or IAA. Exposure to IAA resulted in upregulation of proteins predicted to function in carbohydrate and amino acid transport and exopolysaccharide (EPS) biosynthesis. Metabolite profiles of wild-type cells showed the production of IPA, IAA, and tryptophol, consistent with an active IPA pathway. Finally, we constructed an ΔipdC mutant that showed the elimination of tryptophol, consistent with a loss of IpdC activity, but was still able to produce IAA (20% of wild-type levels). Although we failed to detect intermediates from other known IAA biosynthetic pathways, this result suggests the possibility of an alternate pathway or the production of IAA by a nonenzymatic route in Pantoea sp. YR343. The ΔipdC mutant was able to efficiently colonize poplar, suggesting that an active IPA pathway is not required for plant association.

中文翻译：

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吲哚-3-乙酸的生物合成特征及该植物激素对植物相关微生物泛菌蛋白质组的影响。YR343

吲哚-3-乙酸（IAA）在植物生长和发育中起着核心作用，许多与植物相关的微生物都使用色氨酸作为前体来产生IAA。使用基因组分析，我们预测了Pantoea sp。YR343是一种从美洲杨（Populus deltoides）分离出的微生物，它使用吲哚-3-丙酮酸盐（IPA）途径合成了IAA。为了更好地了解IAA的生物合成和IAA暴露对细胞生理的影响，我们对泛酸的蛋白质组进行了表征sp。YR343在色氨酸或IAA存在下生长。暴露于IAA会导致预计在碳水化合物和氨基酸转运以及胞外多糖（EPS）生物合成中起作用的蛋白质上调。野生型细胞的代谢产物图谱显示IPA，IAA和三氯酚的产生，与有效的IPA途径一致。最终，我们构建了一个ΔipdC突变体，该突变体显示出三氯酚的消除，与IpdC活性的丧失相一致，但仍然能够产生IAA（野生型水平的20％）。尽管我们未能从其他已知的IAA生物合成途径中检测到中间体，但该结果表明在泛菌属中可能存在替代途径或通过非酶途径生产IAA的可能性。YR343。该Δ IPDC 突变体能够有效地定居杨树，这表明植物缔合不需要有效的IPA途径。