From Floral Induction to Blooming: The Molecular Mysteries of Flowering in Woody Plants

Abstract

Flowering is a pivotal developmental process in response to the environment and determines the start of a new life cycle in plants. Woody plants usually possess a long juvenile nonflowering phase followed by an adult phase with repeated flowering cycles. The molecular mechanism underlying flowering regulation in woody plants is believed to be much more complex than that in annual herbs. In this review, we briefly describe the successive but distinct flowering processes in perennial trees, namely the vegetative phase change, the floral transition, floral organogenesis, and final blooming, and summarize in detail the most recent advances in understanding how woody plants regulate flowering through dynamic gene expression. Notably, the florigen gene FLOWERING LOCUS T(FT) and its antagonistic gene TERMINAL FLOWER 1 (TFL1) seem to play a central role in various flowering transition events. Flower development in different taxa requires interactions between floral homeotic genes together with AGL6 conferring floral organ identity. Finally, we illustrate the issues and corresponding measures of flowering regulation investigation. It is of great benefit to the future study of flowering in perennial trees.

Regulatory frameworks involved in the floral induction, formation and developmental programming of woody horticultural plants: a case study on blueberries

“…On the other hand, flowers from seedling-derived fruit trees can only be initiated and developed after the tree reaches adulthood, which can take several years. Even in adult trees, flower initiation and development occur over two growing seasons, not one ( Wilkie et al., 2008 ; Sun et al., 2022 ). For example, floral bud initiation in apple and peach trees occurs in summer and basic morphological structures such as sepal, petal, stamen, and carpel are developed during the fall before entering a fully dormant state, remaining in a “resting” state during winter and then resumed developmental pace before flowering next spring.…”

CONSTANS, a HUB for all seasons: How photoperiod pervades plant physiology regulatory circuits

“…Although CO has been extensively studied in grasses and annual Eudicot plants, recent efforts have been made to understand the role of CO and COL genes in woody or semiwoody species. These species have a longer life cycle and relatively complicated reproductive processes ( Sun et al 2022 ), and CO proteins seem to act as an important factor that integrates photoperiodic signals and circadian rhythms. In grape ( Vitis vinifera ), bud fruitfulness is increased in LD, where the amplitude of VvCO (homolog of Arabidopsis CO) expression is greater.…”

“…All these examples illustrate the complexity of the control of photoperiod-dependent flowering in trees because photoperiod affects not only the transition from vegetative to reproductive phase, as in herbaceous plants, but also bud dormancy ( Hussain et al 2022 ). These 2 complex developmental processes directly influence the year-round cyclic regulation of flowering, which varies between trees adapted to different climates ( Sun et al 2022 ).…”

Identification of Genomic Regions for Traits Associated with Flowering in Cassava (Manihot esculenta Crantz)

“…The flowering process in angiosperms is evoked by an interaction of environmental and endogenous signals [ 13 , 14 , 15 , 16 ]. This is known to be regulated by a sophisticated network that monitors changes in the environment to ensure that flowering occurs under suitable conditions for maximization of reproductive success and seed production [ 17 , 18 ].…”