Abstract
In contrast to animals, adult organs in plants are not formed during embryogenesis but generated from meristematic cells as plants advance through development. Plant development involves a succession of different phenotypic stages and the transition between these stages is termed phase transition. Phase transitions need to be tightly regulated and coordinated to ensure they occur under optimal seasonal, environmental conditions. Polycarpic perennials transition through vegetative stages and the mature, reproductive stage many times during their lifecycles and, in both perennial and annual species, environmental factors and culturing methods can reverse the otherwise unidirectional vector of plant development. Epigenetic factors regulating gene expression in response to internal cues and external (environmental) stimuli influencing the plant’s phenotype and development have been shown to control phase transitions. How developmental and environmental cues interact to epigenetically alter gene expression and influence these transitions is not well understood, and understanding this interaction is important considering the current climate change scenarios, since epigenetic maladaptation could have catastrophic consequences for perennial plants in natural and agricultural ecosystems. Here, we review studies focusing on the epigenetic regulators of the vegetative phase change and highlight how these mechanisms might act in exogenously induced plant rejuvenation and regrowth following stress.
Highlights
Plant development is a step-by-step process causing a gradual alteration in the qualitative and quantitative phenotype of the plant [1]
The vegetative phase change is accompanied by species-specific changes in leaf size and shape, internode length, and trichome distribution, causing a change in the stem appearance, a condition known as heteroblasty [2,3,4]
Phenotypic changes associated with vegetative phase change can be subtle modifications to leaf morphology, such as those observed in certain annual species, or much more dramatic changes affecting the whole structure of the shoots in perennials like Acacia, Eucalyptus, Quercus, and Hedera species [7]
Summary
Plant development is a step-by-step process causing a gradual alteration in the qualitative (germination, flowering, etc.) and quantitative (number of leaves, number of flowers, etc.) phenotype of the plant [1]. During the juvenile vegetative phase, plants are generally insensitive to photoperiod and floral inducers, and with the transition to the adult vegetative phase, they gradually acquire reproductive competence. Phenotypic changes associated with vegetative phase change can be subtle modifications to leaf morphology, such as those observed in certain annual species (e.g., maize [5] and Arabidopsis [6]), or much more dramatic changes affecting the whole structure of the shoots in perennials like Acacia, Eucalyptus, Quercus, and Hedera species [7]. Most of the changes associated with vegetative to reproductive phase transition in annual plants are unidirectional; that is, once the plants enter the adult vegetative phase, they continue forward with the reproductive phase. Most perennial species have a polycarpic growth habit, and they undergo many reproductive cycles during their lifetimes. We discuss the physiological, epigenetic, and genetic control of vegetative phase change and rejuvenation in plants
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