Background

Sweet osmanthus (Osmanthus fragrans) is an ornamental evergreen tree species in China, whose flowers are sensitive to ethylene. The synthesis of ethylene is controlled by key enzymes and restriction enzymes, 1-aminocyclopropane-1-carboxylic acid synthase (ACS) and 1-aminocyclopropane-1-carboxylic acid oxidase (ACO), which are encoded by multigene families. However, the key synthase responsible for ethylene regulation in O. fragrans is still unknown.

Objective

This study aims to screen the key ethylene synthase genes of sweet osmanthus flowers in response to ethylene regulation.

Methods

In this study, we used the ACO and ACS sequences of Arabidopsis thaliana to search for homologous genes in the O. fragrans petal transcriptome database. These genes were also analyzed bioinformatically. Finally, the expression levels of O. fragrans were compared before and after senescence, as well as after ethephon and silver nitrate treatments.

Results

The results showed that there are five ACO genes and one ACS gene in O. fragrans transcriptome database, and the phylogenetic tree revealed that the proteins encoded by these genes had high homology to the ACS and ACO proteins in plants. Sequence alignment shows that the OfACO1-5 proteins have the 2OG-Fe(II) oxygenase domain, while OfACS1 contains seven conserved domains, as well as conserved amino acids in transaminases and glutamate residues related to substrate specificity. Expression analysis revealed that the expression levels of OfACS1 and OfACO1-5 were significantly higher at the early senescence stage compared to the full flowering stage. The transcripts of the OfACS1, OfACO2, and OfACO5 genes were upregulated by treatment with ethephon. However, out of these three genes, only OfACO2 was significantly downregulated by treatment with AgNO₃.

Conclusion

Our study found that OfACO2 is an important synthase gene in response to ethylene regulation in sweet osmanthus, which would provide valuable data for further investigation into the mechanisms of ethylene-induced senescence in sweet osmanthus flowers.

中文翻译：

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桂花花衰老过程中乙烯生物合成基因的表达以及乙烯利和硝酸银处理的响应

背景

桂花（Osmanthus fragrans）是我国常绿观赏树种，其花朵对乙烯敏感。乙烯的合成由关键酶和限制性酶控制，即1-氨基环丙烷-1-羧酸合酶（ACS）和1-氨基环丙烷-1-羧酸氧化酶（ACO），它们由多基因家族编码。然而，香桂中负责乙烯调节的关键合酶仍然未知。

客观的

本研究旨在筛选桂花响应乙烯调控的关键乙烯合酶基因。

方法

在本研究中，我们利用拟南芥的ACO和ACS序列在O.fragrans花瓣转录组数据库中寻找同源基因。还对这些基因进行了生物信息学分析。最后，比较了桂花衰老前后以及乙烯利和硝酸银处理后的表达水平。

结果

结果表明，香桂转录组数据库中有5个ACO基因和1个ACS基因，系统发育树显示这些基因编码的蛋白与植物中的ACS和ACO蛋白具有较高的同源性。序列比对显示，OfACO1-5蛋白具有2OG-Fe(II)加氧酶结构域，而OfACS1包含7个保守结构域，以及转氨酶中的保守氨基酸和与底物特异性相关的谷氨酸残基。表达分析显示，与盛花期相比，OfACS1和OfACO1-5在衰老早期的表达水平显着升高。 OfACS1、OfACO2和OfACO5基因的转录物通过乙烯利处理上调。然而，在这三个基因中，只有OfACO2通过AgNO ₃处理显着下调。

结论

我们的研究发现OfACO2是桂花中响应乙烯调控的重要合酶基因，这将为进一步研究乙烯诱导桂花衰老的机制提供有价值的数据。