Kittiya Tantisuwanichkul, Supaart Sirikantaramas

Plant Physiol Biochem.; 2024 Jan: 206:108253. doi: 10.1016/j.plaphy.2023.108253.3.

Abstract

Durian (Durio zibethinus L.), popularly known as the "King of fruits," holds significant economic importance in Southeast Asia, including Thailand. During its ripening process, the phytohormone abscisic acid (ABA) content has been reported to increase. However, a comprehensive understanding of ABA's specific role in durian fruit ripening remains elusive. Furthermore, little is known about the molecular aspects of the carotenoid cleavage pathway in this iconic fruit. Therefore, we performed genome-wide identification of the carotenoid cleavage oxygenase (CCO) family in durian. This family includes the nine-cis-epoxycarotenoid dioxygenases (NCEDs) responsible for ABA production and the carotenoid cleavage dioxygenases exhibiting diverse substrate specificities. Through phylogenetic analysis, we classified 14 CCOs in durian into 8 distinct subfamilies. Notably, each DzCCO subfamily displayed a conserved motif composition. Cis-acting element prediction showed that cis-elements related to plant hormones and environmental stress responses were distributed in the DzCCO promoter. In addition, transcriptome analysis was performed to examine the expression pattern during the fruit development and ripening stages. Interestingly, DzNCED5a, a ripening-associated gene, exhibited the highest expression level at the ripe stage, outperforming other CCOs. Its expression markedly correlated with increased ABA contents during the ripening stages of both the "Monthong" variety and other durian cultivars. Transiently expressed DzNCED5a in Nicotiana benthamiana leaves confirmed its function in ABA biosynthesis. These findings highlight the involvement of DzNCED5a in ABA production and its potential importance in durian fruit ripening. Overall, this study provides insights into the significance of CCOs in durian fruit ripening.

See: https://pubmed.ncbi.nlm.nih.gov/38086212/

Fig. 1. (A) Phylogenetic tree and (B) conserved motif analysis of CCO proteins from Durio zibethenus, Arabidopsis thaliana, and Solanum lycopersicum. ClustalW was used for multiple alignment. MEGA 11 was used for constructing the tree via neighbor-joining methods with the default parameter (Tamura et al., 2021). The percentage of replicate trees in which the associated taxa clustered together in the bootstrap test (1000 replicates) is shown above the branches (only scores above 60 are shown). The conserved motifs were identified by MEME suit version 5.5.2 (https://meme-suite.org/meme/tools/meme) and visualized with TBtools (Chen et al., 2020).