A survey of the small RNA population during far-red light-induced apical hook opening.

Ying Li,Kranthi Varala,Matthew E Hudson

doi:10.3389/fpls.2014.00156

Ying Li, Kranthi Varala + Show 1 more

Open Access

https://doi.org/10.3389/fpls.2014.00156

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Abstract

Photomorphogenesis is a mechanism employed by plants to regulate their architecture and developmental program in response to light conditions. As they emerge into light for the first time, dark-grown seedlings employ a rapid and finely-controlled photomorphogenic signaling network. Small RNAs have increasingly been revealed to play an important role in regulating multiple aspects of plant development, by modulating the stability of mRNAs. The rapid alteration of the mRNA transcriptome is a known hallmark of the de-etiolation response, thus we investigated the small RNA transcriptome during this process in specific seedling tissues. Here we describe a survey of the small RNA expression profile in four tissues of etiolated soybean seedlings, the cotyledons, hypocotyl and the convex and concave sides of the apical hook. We also investigate how this profile responds to a 1-h far-red light treatment. Our data suggests that miRNAs show a different global profile between these tissues and treatments, suggesting a possible role for tissue- and treatment-specific expression in the differential morphology of the seedling on de-etiolation. Further evidence for the role of miRNA in light-regulated development is given by the de-etiolation responses of a hypomorphic ago1 mutant, which displays reduced and delayed photomorphogenic responses in apical hook and cotyledon angle to far-red light.

Highlights

Light is an essential energy source for plants
THE ago1 MUTANT IS IMPAIRED IN PHOTOMORPHOGENESIS To test whether a functional miRNA system is important for photomorphogenesis, we first investigated the de-etiolation process in an Arabidopsis mutant that is defective in small RNA function
We used the hypomorphic mutant allele ago1-27 (Morel et al, 2002), because the stronger mutant alleles are severely defective in development and sterile, and are not suitable for phenotyping at the seedling stage—this applies to other mutants we are aware of that affect the small RNA machinery

Summary

Introduction

Light is an essential energy source for plants. Plants have evolved a sophisticated system to sense the intensity, wavelength, direction, duration, and diurnal span of environmental light and adjust their developmental plan and architecture. Photomorphogenesis refers to the phenomenon wherein a plant developmentally regulates its body architecture in response to a light stimulus in a non-period-sensitive, non-directional-manner (Smith, 1974; Quail, 2002). A dark-grown dicotyledon seedling displays an elongated hypocotyl, unexpanded, closed cotyledons, closed apical hook, and undifferentiated chloroplasts. De-etiolation occurs after it is exposed to light, and involves an inhibition of hypocotyl elongation, opening of cotyledons and apical hook, and chloroplast maturation. This response would typically be activated at the time that a germinated seedling emerges from soil or leaf litter into sunlight. The timing of de-etiolation is critical to the survival of plants (Quail, 2002), and this process is influenced both by light signals and the plant’s developmental program

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