Beyond the darkness: recent lessons from etiolation and de-etiolation studies.

Omar Sandoval-Ibañez,Tegan Armarego-Marriott,Łucja Kowalewska,Christine Raines

doi:10.1093/jxb/erz496

Abstract

The state of etiolation is generally defined by the presence of non-green plastids (etioplasts) in plant tissues that would normally contain chloroplasts. In the commonly used dark-grown seedling system, etiolation is coupled with a type of growth called skotomorphogenesis. Upon illumination, de-etiolation occurs, marked by the transition from etioplast to chloroplast, and, at the seedling level, a switch to photomorphogenic growth. Etiolation and de-etiolation systems are therefore important for understanding both the acquisition of photosynthetic capacity during chloroplast biogenesis and plant responses to light-the most relevant signal in the life and growth of the organism. In this review, we discuss recent discoveries (within the past 2-3 years) in the field of etiolation and de-etiolation, with a particular focus on post-transcriptional processes and ultrastructural changes. We further discuss ambiguities in definitions of the term 'etiolation', and benefits and biases of common etiolation/de-etiolation systems. Finally, we raise several open questions and future research possibilities.

Highlights

The state of etiolation is generally defined by the presence of non-green plastids in plant tissues that would normally contain chloroplasts
The prolamellar body (PLB) consists largely of the plastid lipids monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), and an association of the chlorophyll precursor protochlorophyllide (Pchlide), the lightdependent protochlorophyllide oxidoreductase (LPOR) that is responsible for its conversion, and the cofactor NADPH
In light of a recently clarified position for target of rapamycin (TOR) in the constitutively photomorphogenic 1 (COP1)– auxin cascade (Chen et al, 2018a), these findings suggest that TOR balances light and sugar signaling to control plant and plastid development both at near-instantaneous and at more gradual time scales (Fig. 2C)

Summary

Introduction

The state of etiolation is generally defined by the presence of non-green plastids (etioplasts) in plant tissues that would normally contain chloroplasts.

Results

Conclusion