Transcriptomics analysis of mangosteen ripening revealed active regulation of ethylene, anthocyanin and xanthone biosynthetic genes

Abstract

Mangosteen (Garcinia mangostana Linn.) is known as the ‘Queen of Fruits’ due to its sweet and unique taste. The fruit also contains beneficial compounds such as anthocyanins and xanthones which have pharmacological properties including anticancer, and anti-inflammatory activities. Mangosteen has unique ripening behavior whereby the fruit undergoes full ripening (up to Stage 6 (S6), dark purple) only when harvested at the middle ripening stage (Stage 2 (S2), appearance of pink spots) onwards. This is unlike most other climacteric fruits which can ripen completely when harvested at the initial green stage (Stage 0, S0). However, information governing the ripening regulation of mangosteen is limited particularly at the molecular level. Hence, transcriptomics analyses on mangosteen pericarp was performed at different ripening stages; S0 (initial stage), S2 (middle stage), and S6 (final stage), revealing 250,680 unique transcripts, of which 6233 were differentially expressed transcripts (DETs). Furthermore, the benchmarking universal single-copy orthologs (BUSCO) analysis affirmed that the assembled transcriptome contains 93.8 % of gene representation in the Viridiplantae kingdom. Functional annotation indicated a high match with the species from the Malpighiales order, with most of the DETs participating in the metabolism process. Additionally, transcriptomics analysis indicated the fruit undergoes transitioning at the early ripening (S0 vs S2) by conserving carbon skeleton instead of energy production before ethylene surge later (S2 vs S6). Transcripts relating to the anthocyanin and xanthone biosynthesis were upregulated during ripening particularly at an early stage, consistent with ripening as an oxidative process with high requirements of antioxidants. This study contributes to the findings of novel transcripts important for the regulation of ripening which could lead to better commercial utilization and preservation of mangosteen in the future.