Analysis on Cloning of AOS1 Gene and Its Expression Pattern During the Browning Process in Fresh-cut Taros

Abstract

【Objective】Fresh-cut taro is prone to turning yellow and brown during storage, even stored at low temperature, which greatly diminishes its commercial values. In order to identify the important functional genes involved in the browning process of fresh-cut taro, the allene oxide synthase (AOS) gene AOS1 was cloned from fresh-cut taros.The correlation between the expression of AOS1 and the browning development of fresh-cut taro was analyzed, with a view to offering references for the study of taro browning mechanism.【Method】With cDNA of fresh-cut taro as a template, the coding sequence (CDS) of AOS1 gene was cloned by the RT-PCR method. The expression patterns of AOS1 during the browning of fresh-cut taro were analyzed by using qRT-PCR, the impact of exogenous browning inhibitors on AOS1 expression was examined by using transcriptome sequencing data, and the promoter subsequence was analyzed.【Result】Fresh-cut taros showed obvious yellowing and browning symptoms on the cut surface after 24 hours of storage at 20 ℃, while the obvious browning symptoms were occurred after 12 d of cold storage at 4 ℃. These results suggested that storage temperature was a crucial factor influencing the browning process of fresh-cut taros, with low temperature storage effectively inhibiting the browning. The CDS of taro AOS1 gene had a total length of 1 560 bp and encoded 519 amino acid residues. The molecular weight of the protein encoded by AOS1 gene was 57.63 kD, with an isoelectric point of 8.68, and located in chloroplast. The similarity of AOS1 protein sequences across different plant species was relatively low, with notable differences observed between taro, tomato, and Arabidopsis. However, high sequence homology was found among AOS1 proteins in Araceae family plants. The promoter region of taro AOS1 contained various plant hormone and stress response elements. The expression of AOS1 significantly increased after fresh-cut processing, indicating that the cutting treatment induced AOS1 expression. Moreover, as the browning of freshcut taro progressed, the expression of AOS1 gradually increased. Applications of exogenous glycolic acid and vanillic acid significantly decreased the expression of AOS1 in fresh-cut taros, showing its correlation with the browning process.【Conclusion】A significant positive correlation was observed between the browning of fresh-cut taros and the expression of AOS1 during cold storage. Treatments such as cutting and peeling may accelerate the browning process by inducing AOS1 expression.

Keywords

• fresh-cut taro
• browning
• allene oxide synthase
• gene cloning
• expression analysis