The Cold Awakening of Doritaenopsis ‘Tinny Tender’ Orchid Flowers: The Role of Leaves in Cold-induced Bud Dormancy Release

Abstract

Massive flowering of tropical Phalaenopsis orchids is coordinated by the cold-induced release of reproductive bud dormancy. Light and temperature are the two key factors integrated by the dormancy mechanism to both stop and reactivate the meristem development of many other angiosperm species, including fruit trees and ornamental plants. It is well established that leaves and roots play a major role in inducing flower development; however, currently, knowledge of molecular events associated with reproductive bud dormancy release in organs other than the bud is limited. Using differential gene expression, we have shown that the leaves of a hybrid of Phalaenopsis species, Doritaenopsis 'Tinny Tender', undergo major metabolic modifications. These changes result in the production of sucrose and amino acids, both of which can sustain bud outgrowth, and auxin and ethylene, which may play important roles in awaking the dormant buds. Intake of abscisic acid and synthesis of the hormone jasmonate may also explain the inhibition of vegetative growth that coincides with bud growth. Interestingly, many genes that were upregulated by cold treatment are homologous for genes involved in flower induction and vernalization in Arabidopsis, indicating that processes regulating flowering induction and those regulating reproductive bud dormancy release may use similar pathways and effector molecules.

Can a high red: Far red ratio replace temperature-induced inflorescence development in Phalaenopsis?

“…Such a response may decrease the necessity of low temperature for development of multiple inflorescences. Additionally, or alternatively, there may be a possible role for phytochrome A (Qin et al, 2012), which inhibits flowering in short day plants (Hayama and Coupland, 2004), but it is uncertain whether or not Phalaenopsis functions like to a short Table 1 The light and temperature treatments used for flower induction of Phalaenopsis. Wk 1-8 denotes week 1 through 8 starting at the beginning of the experiment.…”

Comprehensive analysis of the longan transcriptome reveals distinct regulatory programs during the floral transition

“…In apple, TPS displays a gradual increase during flower induction [48]. In addition, expression of sugar biosynthesis-related genes such as SS2 , GBSS , and SUS increase during floral induction in Litchi and Doritaenopsis [49, 50]. Compared to ‘SX’, almost all DEGs related to starch and sucrose metabolism pathways were significantly altered during the T1 to T2 transition in ‘SJ’, whereas only 5 starch and sucrose-related DEGs changed significantly during the T2 to T3 transition.…”

Transcriptome profiling of litchi leaves in response to low temperature reveals candidate regulatory genes and key metabolic events during floral induction

“…Plants integrate diverse environmental and endogenous signals to ensure the timely transition from vegetative growth to flowering, which is a consuming energy process while the energy mainly comes from carbohydrates. Carbohydrates are thought to play a crucial role in the regulation of flowering, and many previous studies suggested the content of carbohydrates is correlated with floral formation in some horticultural plants [ 13 , 17 , 61 – 63 ]. Recently, trehalose-6-phosphate (T6P) has been suggested to function as a proxy for carbohydrate status in plants, trehalose-6-phosphate synthase 1 ( TPS1 ) is essential for normal vegetative growth and transition to flowering in Arabidopsis, the loss of TPS1 causes Arabidopsis thaliana to flower extremely late, even under otherwise inductive environmental conditions [ 64 , 65 ].…”

“…After exposure to low temperature for several weeks to induce flowering, litchi trees start floral initiation and morphological development with ascending temperature, subsequently, bloom in spring with favorable conditions [ 1 ]. Previous studies have shown that low temperature is a crucial environmental cue for floral induction of subtropical evergreen plants, litchi [ 2 – 6 ], olive [ 7 ], mango [ 8 , 9 ], citrus [ 10 – 12 ] and orchid [ 13 ], all of which require a certain period of relatively low temperature to induce flowering. However, besides low temperature, internal factors like state of branches (including buds and leaves) can also result in irregularities in litchi flowering [ 14 ].…”