Koeduka Takao, Ito Karin, Yamamoto Shin-Nosuke, Ozaki Shin-Ichi, Tsuge Tomohiko, Kitajima Sakihito
Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi, 753-8515, Japan.
Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan.
Plant Mol Biol. 2025 May 31;115(3):70. doi: 10.1007/s11103-025-01597-3.
Benzoic acid, the simplest aromatic carboxylic acid, is an important building block for a wide range of primary and specialized plant metabolites. In Petunia hybrida, benzoic acid serves as a key precursor of volatile benzenoids, which are responsible for the primary floral scent. However, the enzymes responsible for benzoic acid production in plants have rarely been reported. This study aimed to identify and characterize benzaldehyde dehydrogenases-enzymes that catalyze the oxidation of benzaldehyde to benzoic acid-using a combination of metabolite analysis and transcriptomic approaches. We identified two petunia benzaldehyde dehydrogenases, PhBALDH-1 and PhBALDH-2, with apparent K values of 93 and 51 μM for benzaldehyde, respectively. While PhBALDH-2 exhibited a strong preference for NAD as a cofactor, PhBALDH-1 was capable of utilizing both NAD and NADP. In vitro mutagenesis experiments demonstrated that substituting a single amino acid markedly affected the cofactor specificity of the PhBALDH-1 enzyme. Gene expression analysis during petunia flower development suggests that both PhBALDH-1 and PhBALDH-2 are likely involved in regulating volatile benzenoid biosynthesis in petunia flowers. Our findings provide functional insights into the biosynthesis of benzoic acid and its regulation in P. hybrida.
苯甲酸是最简单的芳香族羧酸，是多种初级和特殊植物代谢产物的重要组成部分。在矮牵牛中，苯甲酸是挥发性苯类化合物的关键前体，这些化合物构成了花朵的主要香气。然而，植物中负责苯甲酸生成的酶鲜有报道。本研究旨在结合代谢物分析和转录组学方法，鉴定并表征苯甲醛脱氢酶（催化苯甲醛氧化为苯甲酸的酶）。我们鉴定出两种矮牵牛苯甲醛脱氢酶，PhBALDH - 1和PhBALDH - 2，它们对苯甲醛的表观K值分别为93和51 μM。虽然PhBALDH - 2对辅酶NAD有强烈偏好，但PhBALDH - 1能够利用NAD和NADP。体外诱变实验表明，替换单个氨基酸会显著影响PhBALDH - 1酶的辅酶特异性。矮牵牛花朵发育过程中的基因表达分析表明，PhBALDH - 1和PhBALDH - 2都可能参与调控矮牵牛花朵中挥发性苯类化合物的生物合成。我们的研究结果为矮牵牛中苯甲酸的生物合成及其调控提供了功能方面的见解。
