Transcriptomic, proteomic and metabolomic analysis of UV-B signaling in maize

Paula Casati,Darren J Morrow,Mabel Campi,Virginia Walbot,John F Fernandes

doi:10.1186/1471-2164-12-321

Abstract

BackgroundUnder normal solar fluence, UV-B damages macromolecules, but it also elicits physiological acclimation and developmental changes in plants. Excess UV-B decreases crop yield. Using a treatment twice solar fluence, we focus on discovering signals produced in UV-B-irradiated maize leaves that translate to systemic changes in shielded leaves and immature ears.ResultsUsing transcriptome and proteomic profiling, we tracked the kinetics of transcript and protein alterations in exposed and shielded organs over 6 h. In parallel, metabolic profiling identified candidate signaling molecules based on rapid increase in irradiated leaves and increased levels in shielded organs; pathways associated with the synthesis, sequestration, or degradation of some of these potential signal molecules were UV-B-responsive. Exposure of just the top leaf substantially alters the transcriptomes of both irradiated and shielded organs, with greater changes as additional leaves are irradiated. Some phenylpropanoid pathway genes are expressed only in irradiated leaves, reflected in accumulation of pathway sunscreen molecules. Most protein changes detected occur quickly: approximately 92% of the proteins in leaves and 73% in immature ears changed after 4 h UV-B were altered by a 1 h UV-B treatment.ConclusionsThere were significant transcriptome, proteomic, and metabolomic changes under all conditions studied in both shielded and irradiated organs. A dramatic decrease in transcript diversity in irradiated and shielded leaves occurs between 0 h and 1 h, demonstrating the susceptibility of plants to short term UV-B spikes as during ozone depletion. Immature maize ears are highly responsive to canopy leaf exposure to UV-B.

Highlights

Under normal solar fluence, UV-B-irradiated leaves for h (UV-B) damages macromolecules, but it elicits physiological acclimation and developmental changes in plants
In a pilot experiment we discovered that shielded organs, such as leaves wrapped in UV-B filters and immature ears encased in the husk leaves, show transcriptome changes within an hour or two after canopy leaves receive UV-B [10]
Experimental samples were recovered from plants with partial shielding (Figure 1b); top canopy leaves were irradiated but other fully expanded leaves and immature ears were shielded from direct UV-B exposure

Summary

Introduction

UV-B damages macromolecules, but it elicits physiological acclimation and developmental changes in plants. The ozone shield against UV-B is not expected to stabilize at 1950 levels until ~2050 [2]; determining the molecular bases for acclimation to normal fluence and tolerance of higher fluence UV-B are important factors in sustaining crop yield as the world’s population continues to increase. Temperate maize with knockdowns in chromatin remodeling factors exhibit adult tissue hypersensitivity and seedling lethality after mild UV-B supplementation [5,6]. These and studies on other plants implicate both metabolite and gene expression responses as critical for short-term acclimation to UV-B and as examples of plant adaptation to this environmental variable [7,8,9]

Methods

Results

Discussion

Conclusion