Role of Phytohormones and Light in De-etiolation

Abstract

Abstract De-etiolation or transition from etiolated growth (skotomorphogenesis) to photomorphogenesis is one of the most intriguing and intricate stages of plant ontogenesis. It comprises reprogramming of plant cell metabolism, reorganizing the operation of the hormonal system, and altering plant morphology. Dark growth in the soil mainly depends on phytohormones with gibberellins and brassinosteroids playing the leading role; on the soil surface, light as a major exogenous agent starts operating. It inhibits activity of the main repressor of photomorphogenesis (COP1) and regulators of transcription, which govern realization of gibberellin (DELLA) and brassinosteroid (BZR1/BES1) signals and activates trans-factors initiating transition to autotrophic nutrition (for instance, HY5). The strategy of etiolated growth consists in achieving a quick exposure to sunlight at the expense of active elongation of the stem. For transition to autotrophic nutrition, a plant must form a photosynthetic apparatus and protect itself from possible light injury. This review deals with the role of the main regulatory components ensuring etiolated growth and transition to photomorphogenic development.