Suggesting a prospect for melatonin-mediated orchid flowering under extreme conditions

• Published in: Scientia horticulturae Vol. 321; p. 112340
• Main Authors: Ahmad, Sagheer, Wang, Fei, Ahmad, Aqeel, Ercisli, Sezai, Chen, Jinliao, Guan, Yunxiao, Zhao, Kai, Zhou, Yuzhen, Lan, Siren, Liu, Zhongjian, Peng, Donghui
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.2023
• Subjects: abiotic stress; Abiotic stress tolerance; acetyltransferases; aesthetics; biosynthesis; caffeate O-methyltransferase; champagne; Cymbidium; flowers; gene expression regulation; growth and development; homeostasis; Leafless orchids; melatonin; Melatonin regulation; prices; serotonin; stress tolerance; Transcriptomes; transcriptomics; tryptophan; Tryptophan pathway; vegetative growth; Transcriptomes; Melatonin regulation; Abiotic stress tolerance; Leafless orchids; Tryptophan pathway
• ISSN: 0304-4238
• DOI: 10.1016/j.scienta.2023.112340

•Cymbidium orchids are the most valuable flowers with a long vegetative phase (2–3 years).•We obtained leafless flowers for three Cymbidium species through a special media combination in tissue culture. These can be excellent resources to study abiotic stress tolerance.•Comparative transcriptome between leafless flowers and healthy leaves provides important clues about melatonin-mediated flowering, which has not been documented before in orchids.•A number of DEGs were found for Tryptophan pathway with contrasting expression patterns between leafless flowers and healthy leaves of three Cymbidium species. Abiotic stress is a major constraint in the successful growth and development of ornamental plants under severe conditions. Since antiquity, melatonin homeostasis has been an effective contrivance in the strategies of abiotic stress tolerance in plants, although it is completely neglected in orchids, the champagne of flowers. Orchids with exceptionally long vegetative phase face a number of stresses and, therefore, stress alleviation has been a hot topic in orchid cultivation. The in-vitro flowering is a useful method for early identification of hybrids in crop improvement programs. We successfully achieved in-vitro leafless flowering in three Cymbidium orchids (C. sinense, C. goeringii and C. ensifolium), which are elite flowers in terms of versatile flower shapes, esthetic preference and price. Transcriptomic analysis was performed to compare the leafless flowers with leaves to identify genes related to tryptophan pathway and melatonin biosynthesis. More than 50 differentially expressed genes (DEGs) were identified in each species with contrasting expressions in the leafless flowers and leaves. The important melatonin pathway genes included serotonin N-acetyltransferase (SNAT), caffeic acid 3-O-methyltransferase (CAMT) and tryptophan decarboxylase (TDC). Moreover, clustering analysis pointed out the significant abiotic stress tolerance-related genes. This opening report, thus, provides a robust cradle to idealize the melatonin as an effective abiotic stress regulator to aid the long journey of vegetative growth and then flowering in precious orchids.