Paclobutrazol is a highly efficient plant growth regulator that functions by inhibiting the biosynthesis of gibberellins, which are plant hormones responsible for stem elongation and other growth processes[1]. Paclobutrazol can be absorbed by plant roots and transported to the stem, making it an important tool for modulating plant structure and enhancing agricultural productivity[2]. Studies have shown that the inhibitory effect of Paclobutrazol on gibberellin production varies among different plant species but generally lies in the low micromolar range [3]. Additionally, Paclobutrazol has been found to cause embryotoxicity in zebrafish[4].
In vitro, pre-treatment of HepaRG hepatocytes with Paclobutrazol (90–360µM) for 72 hours significantly reduced cell viability, increased oxidative stress levels, and elevated the apoptosis rate. Moreover, Paclobutrazol impaired autophagy by inhibiting the AMPK/mTOR signaling pathway, thereby exacerbating apoptosis[5]. Pre-treatment of free endosperm cells from Cucurbita maxima with Paclobutrazol (9.5nM) significantly inhibited the activity of ent-kaurene oxidase. Additionally, the azido derivative of Paclobutrazol (AZP) bound to cytochrome P450 in Cucurbita maxima microsomes and induced a Type II spectral change, with an apparent binding constant of 0.24±0.04µM[6].
In vivo, exposure of zebrafish (Danio rerio) to Paclobutrazol (10mg/L) for 14 days significantly induced oxidative stress, increased the levels of malondialdehyde (MDA) and protein carbonyl (PC), and decreased the activities of superoxide dismutase (SOD) and catalase (CAT). Paclobutrazol also exhibited neurotoxicity in zebrafish[7]. Paclobutrazol (32.5mg/kg and 260mg/kg) was administered via gavage to 6–8-week-old Sprague-Dawley rats for 28 days. Paclobutrazol significantly reduced the levels of thyroid hormone T4 in rat serum, increased thyroid follicular cell inflammation and follicular deformation, and disrupted the function of the thyroid endocrine system[8].
References:
[1] Xu Y, Zhu Y, Wang X, et al. PACLOBUTRAZOL-RESISTANCE4 positively regulates cell expansion to promote tendril elongation in cucumber. Plant Physiol. 2023 Aug 3;192(4):2756-2767.
[2] Urfan M, Hakla HR, Sharma S, et al. Paclobutrazol improves surface water use efficiency by regulating allometric trait behavior in maize. Chemosphere. 2022 Nov;307(Pt 3):135958.
[3] Zhang Y, He Z, Xing P, et al. Effects of paclobutrazol seed priming on seedling quality, photosynthesis, and physiological characteristics of fragrant rice. BMC Plant Biol. 2024 Jan 17;24(1):53.
[4] Hussain A, Audira G, Siregar P, et al. Waterborne Exposure of Paclobutrazol at Environmental Relevant Concentration Induce Locomotion Hyperactivity in Larvae and Anxiolytic Exploratory Behavior in Adult Zebrafish.
[5] Luo Y, Lu S, Sun X, et al. Paclobutrazol exposure induces apoptosis and impairs autophagy in hepatocytes via the AMPK/mTOR signaling pathway. J Biochem Mol Toxicol. 2021 Oct;35(10):e22874.
[6] Hallahan DL, Heasman AP, Grossel MC, et al. Synthesis and biological activity of an azido derivative of paclobutrazol, an inhibitor of gibberellin biosynthesis. Plant Physiol. 1988 Dec;88(4):1425-9.
[7] Guo D, Luo L, Kong Y, et al. Enantioselective neurotoxicity and oxidative stress effects of paclobutrazol in zebrafish (Danio rerio). Pestic Biochem Physiol. 2022 Jul;185:105136.
[8] Liu H, Xu Y, Wang Y, et al. Study on endocrine disruption effect of paclobutrazol and uniconazole on the thyroid of male and female rats based on lipidomics. Ecotoxicol Environ Saf. 2022 Apr 1;234:113386.
Paclobutrazol是一种高效的植物生长调节剂，通过抑制赤霉素（一种负责茎伸长和其他生长过程的植物激素）的生物合成发挥作用[1]。Paclobutrazol可被植物根部吸收并转运至茎部，是调节植物结构和提高农业生产力的重要工具[2]。研究发现，Paclobutrazol对赤霉素生产的抑制作用在不同植物种类中有所不同，但通常处于低微摩尔范围[3]。此外，Paclobutrazol会引起斑马鱼胚胎毒性[4]。
在体外，Paclobutrazol（90–360μM）预处理HepaRG肝细胞72小时后，细胞活性显著下降，氧化应激水平升高，细胞凋亡率增加。此外，Paclobutrazol还通过抑制AMPK/mTOR信号通路，损害细胞自噬功能，进而加剧细胞凋亡[5]。Paclobutrazol（9.5nM）预处理南瓜（Cucurbita maxima）游离胚乳细胞后，能够显著抑制ent-kaurene氧化酶的活性。此外，Paclobutrazol的叠氮衍生物（AZP）能够与南瓜胚乳微粒体中的细胞色素P450结合，并诱导II型光谱变化，结合常数为0.24±0.04μM [6]。
在体内，Paclobutrazol（10mg/L）暴露于斑马鱼（Danio rerio）14天，显著诱导氧化应激，增加丙二醛（MDA）和蛋白羰基（PC）含量，并降低超氧化物歧化酶（SOD）和过氧化氢酶（CAT）活性。同时，Paclobutrazol显示出对斑马鱼具有神经毒性[7]。Paclobutrazol（32.5mg/kg和260mg/kg）通过灌胃给药，处理6–8周龄的Sprague-Dawley大鼠，持续28天。Paclobutrazol显著降低了大鼠血清中甲状腺激素T4水平，增加了甲状腺滤泡细胞炎症和滤泡变形，干扰了甲状腺内分泌系统的功能[8]。