Carnation (Dianthus caryophyllus L.) is a prominent floricultural crop valued for its diverse colors, offering significant economic and ornamental value globally. However, the global demand for its flowers makes flower yield an important attribute that relies on the quantity of lateral branches in the crop. Melatonin as a multi-regulatory phytohormone play vital functions in governing plant growth and development. It is synthesized from tryptophan via four key enzymes. Tryptophan decarboxylase (TDC), Tryptamine 5-hydroxylase (T5H), Serotonin N-acetyltransferase (SNAT), and N-Acetylserotonin O-methyltransferase (ASMT). Although the significance of melatonin is recognized, its impact on the growth and development of carnation remains understudied. In the current study, we investigated the effect of exogenous melatonin at different concentrations, on growth pattern of carnation, followed by genome-wide characterization, in-silico analysis and expression profiling of melatonin biosynthetic pathway genes. Results showed increased branching and reduced height with increased melatonin concentrations up to a point. In-silico analysis identified ten genes in the melatonin biosynthetic pathway, including two TDC, two T5H, one SNAT, and five ASMT members. Domain analysis confirmed the presence of characteristic domains such as pyridoxal-dependent decarboxylase, cytochrome P450, Acetyltransferase_1, and O-methyltransferase. Physiochemical properties, gene structure, conserved motifs, promoter regions, gene ontology, synteny, and evolutionary relationships through phylogeny were also analysed. Sub-cellular localization predictions showed distribution of melatonin biosynthetic enzymes across various cellular compartments. Expression analysis of these genes under different exogenous melatonin concentrations (100, 200, 300, 400, 500, and 1000 µM) revealed significant upregulation at 100 µM and 500 µM, while no change was observed at 1000 µM. These findings suggest that optimal exogenous melatonin concentrations enhance the expression of biosynthetic pathway genes ultimately led to increased branching in carnation due to increased endogenous melatonin levels. This study establishes a basis for future functional characterization of melatonin biosynthetic pathway genes to elucidate their roles in carnation growth and development.

中文翻译：

---

康乃馨 （Dianthus caryophyllus L.） 中褪黑激素生物合成途径基因的全基因组表征及其响应外源褪黑激素的表达分析


康乃馨 （Dianthus caryophyllus L.） 是一种著名的花卉作物，因其多样化的颜色而受到重视，在全球范围内具有重要的经济和观赏价值。然而，全球对其花的需求使花产量成为一个重要的属性，它依赖于作物中侧枝的数量。褪黑激素作为一种多调节植物激素，在控制植物生长和发育中起着至关重要的作用。它是由色氨酸通过四种关键酶合成的。色氨酸脱羧酶 （TDC）、色胺 5-羟化酶 （T5H）、血清素 N-乙酰转移酶 （SNAT） 和 N-乙酰血清素 O-甲基转移酶 （ASMT）。尽管褪黑激素的重要性已得到认可，但其对康乃馨生长发育的影响仍未得到充分研究。在本研究中，我们研究了不同浓度的外源褪黑激素对康乃馨生长模式的影响，然后对褪黑激素生物合成途径基因进行了全基因组表征、计算机分析和表达谱分析。结果显示，随着褪黑激素浓度的增加，分枝增加，高度降低。计算机模拟分析在褪黑激素生物合成途径中鉴定了 10 个基因，包括 2 个 TDC 、 2 个 T5H 、 1 个 SNAT 和 5 个 ASMT 成员。结构域分析证实存在特征结构域，例如吡哆醛依赖性脱羧酶、细胞色素 P450、Acetyltransferase_1 和 O-甲基转移酶。还分析了理化性质、基因结构、保守基序、启动子区域、基因本体论、同线和通过系统发育的进化关系。亚细胞定位预测显示褪黑激素生物合成酶分布在各个细胞区室中。 这些基因在不同外源褪黑激素浓度 （100 、 200 、 300 、 400 、 500 和 1000 μM） 下的表达分析显示，在 100 μM 和 500 μM 时显著上调，而在 1000 μM 时未观察到变化。这些发现表明，最佳的外源褪黑激素浓度增强了生物合成途径基因的表达，最终导致由于内源性褪黑激素水平增加，康乃馨的分支增加。本研究为褪黑激素生物合成途径基因的未来功能表征奠定了基础，以阐明它们在康乃馨生长发育中的作用。