Abstract
BackgroundManipulation of flowering time and frequency of blooming is key to enhancing the ornamental value of orchids. Arundina graminifolia is a unique orchid that flowers year round, although the molecular basis of this flowering pattern remains poorly understood.ResultsWe compared the A. graminifolia transcriptome across tissue types and floral developmental stages to elucidate important genetic regulators of flowering and hormones. Clustering analyses identified modules specific to floral transition and floral morphogenesis, providing a set of candidate regulators for the floral initiation and timing. Among candidate floral homeotic genes, the expression of two FT genes was positively correlated with flower development. Assessment of the endogenous hormone levels and qRT-PCR analysis of 32 pathway-responsive genes supported a role for the regulatory networks in floral bud control in A. graminifolia. Moreover, WGCNA showed that flowering control can be delineated by modules of coexpressed genes; especially, MEgreen presented group of genes specific to flowering.ConclusionsCandidate gene selection coupled with hormonal regulators brings a robust source to understand the intricate molecular regulation of flowering in precious orchids.
Highlights
Manipulation of flowering time and frequency of blooming is key to enhancing the ornamental value of orchids
A. graminifolia blooms all year round, with the most vigorous flowering from September to January (Supplementary Fig. 1)
Correlation between the endogenous hormones and flower development To validate the effect of hormones on flower development, we investigated the levels of endogenous hormones—cytokinins (CK), gibberellic acid (GA), abscisic acid (ABA), brassinosteroid (BR), jasmonic acid (JA), 1-Aminocyclopropane-1-carboxylic acid (ACC), and indoleacetic acid (IAA)—at different growth stages (Fig. 3b)
Summary
Manipulation of flowering time and frequency of blooming is key to enhancing the ornamental value of orchids. The time of flowering is crucial for the species to adapt in their environment as their life cycle runs depending on the fine combination of intrinsic and extrinsic stimuli. Stability of flowering time is the key goal for breeding endeavors. Environmental variations, such as changes in light, temperature, and hormone levels, control flower quality and flowering time [2]. Flowering time in Arabidopsis depends on five genetic pathways: photoperiod, aging, gibberellin, vernalization, and autonomous pathways [3]. These pathways are integrated by floral integrators, including SUPPRESSOR OF OVEREXPRESSION OF CO
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