The Genetic and Hormonal Inducers of Continuous Flowering in Orchids: An Emerging View

Abstract

Orchids are the flowers of magnetic beauty. Vivid and attractive flowers with magnificent shapes make them the king of the floriculture industry. However, the long-awaited flowering is a drawback to their market success, and therefore, flowering time regulation is the key to studies about orchid flower development. Although there are some rare orchids with a continuous flowering pattern, the molecular regulatory mechanisms are yet to be elucidated to find applicable solutions to other orchid species. Multiple regulatory pathways, such as photoperiod, vernalization, circadian clock, temperature and hormonal pathways are thought to signalize flower timing using a group of floral integrators. This mini review, thus, organizes the current knowledge of floral time regulators to suggest future perspectives on the continuous flowering mechanism that may help to plan functional studies to induce flowering revolution in precious orchid species.

Keywords: continuous flowering; hormones; key regulators; miRNAs; orchids; transcription factors.

Figure 1

The summary of important transcription factors in the regulation of flowering in orchids. Most of these transcription factors have been identified in continuous flowering orchid A. graminifolia [1,73].

Figure 2

Proposed key miRNAs that may play a role in continuous flowering regulation in orchids.

Figure 3

Hypotheses on multiple pathway regulation of continuous flowering in orchids, specifically the A. graminifolia, independent of TFL1. It may serve as a basis to study the phenomenon of continuous flowering in seasonal orchids. The color of circles shows the observed expression of different pathway genes in A. graminifolia [1].