A comparative analysis of transcriptomic, biochemical, and physiological responses to elevated ozone identifies species-specific mechanisms of resilience in legume crops.

Craig R Yendrek,Elizabeth A Ainsworth,Robert P Koester

doi:10.1093/jxb/erv404

Abstract

Current concentrations of tropospheric ozone ([O3]) pollution negatively impact plant metabolism, which can result in decreased crop yields. Interspecific variation in the physiological response of plants to elevated [O3] exists; however, the underlying cellular responses explaining species-specific differences are largely unknown. Here, a physiological screen has been performed on multiple varieties of legume species. Three varieties of garden pea (Pisum sativum L.) were resilient to elevated [O3]. Garden pea showed no change in photosynthetic capacity or leaf longevity when exposed to elevated [O3], in contrast to varieties of soybean (Glycine max (L.) Merr.) and common bean (Phaseolus vulgaris L.). Global transcriptomic and targeted biochemical analyses were then done to examine the mechanistic differences in legume responses to elevated [O3]. In all three species, there was an O3-mediated reduction in specific leaf weight and total non-structural carbohydrate content, as well as increased abundance of respiration-related transcripts. Differences specific to garden pea included a pronounced increase in the abundance of GLUTATHIONE REDUCTASE transcript, as well as greater contents of foliar glutathione, apoplastic ascorbate, and sucrose in elevated [O3]. These results suggest that garden pea may have had greater capacity for detoxification, which prevented net losses in CO2 fixation in an elevated [O3] environment.

Highlights

One of the most harmful air pollutants impacting plant growth today is tropospheric ozone (O3; Krupa et al, 2001)
Garden pea displayed no visual signs of O3 damage in contrast to soybean and common bean, which both had signs of chlorosis (Fig. 2A)
No significant change in leaf longevity was detected in garden pea grown in elevated [O3], while a 12–15 day decrease in soybean and common bean was seen (Fig. 2B)

Summary

Introduction

One of the most harmful air pollutants impacting plant growth today is tropospheric ozone (O3; Krupa et al, 2001). The abundance and redox states of the antioxidants ascorbate and glutathione are important for detoxification of O3-induced ROS (Foyer and Noctor, 2005), and act to prevent cellular damage and maintain normal metabolic activity. Transgenic approaches have been used to alter the abundance and/or redox state of the ascorbate and/or glutathione pools in order to better understand the mechanisms of cellular O3 response These studies have highlighted the complexity of O3-induced oxidative signalling, which depends on the coordinated expression of specific ascorbate–glutathione cycle isoenzymes in the correct subcellular compartments to maintain redox homeostasis (Noctor and Foyer, 1998; Foyer and Noctor, 2005). Complicating the comparison between these two studies are different O3 exposures (concentration and duration) used to screen the transgenic plants

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