GABA Shunt in Durum Wheat.

Petronia Carillo

doi:10.3389/fpls.2018.00100

Abstract

Plant responses to salinity are complex, especially when combined with other stresses, and involve many changes in gene expression and metabolic fluxes. Until now, plant stress studies have been mainly dealt only with a single stress approach. However, plants exposed to multiple stresses at the same time, a combinatorial approach reflecting real-world scenarios, show tailored responses completely different from the response to the individual stresses, due to the stress-related plasticity of plant genome and to specific metabolic modifications. In this view, recently it has been found that γ-aminobutyric acid (GABA) but not glycine betaine (GB) is accumulated in durum wheat plants under salinity only when it is combined with high nitrate and high light. In these conditions, plants show lower reactive oxygen species levels and higher photosynthetic efficiency than plants under salinity at low light. This is certainly relevant because the most of drought or salinity studies performed on cereal seedlings have been done in growth chambers under controlled culture conditions and artificial lighting set at low light. However, it is very difficult to interpret these data. To unravel the reason of GABA accumulation and its possible mode of action, in this review, all possible roles for GABA shunt under stress are considered, and an additional mechanism of action triggered by salinity and high light suggested.

Highlights

The synthesis of γ-aminobutyric acid (GABA) in particular, and in minor way of other amino acids including proline, remodeled metabolism and defense processes, playing a key role in the response to simultaneous stresses (Woodrow et al, 2017). This result is worthy of attention because most of the studies done on cereal seedlings under salinity have been performed in controlled environment chambers operated with low-medium light levels up to about 300–350 μmol m−2 s−1 photosynthetic active radiation (PAR) corresponding to a daily light integral (DLI) of about 17–20 mol m−2 d−1 with a 16-h photoperiod (Annunziata et al, 2017)
Durum wheat plants growing in natural environments, on the contrary, can experience, in a clear day, light intensities rising up to 900 and 2000 μmol m−2 s−1 in winter and summer, respectively, which exceed their photosynthetic capacity (Carillo et al, 2011b)
GABA is a non-protein amino acid that was first discovered in plants, being highly accumulated in response to biotic and abiotic stresses included senescence, and in animal mature brain, where it plays a major role as an inhibitory neurotransmitter (Michaeli and Fromm, 2015)

Summary

Petronia Carillo*

Dipartimento di Scienze e Tecnologie Ambientali, Biologiche e Farmaceutiche, Università degli Studi della Campania “Luigi Vanvitelli”, Caserta, Italy. Plants exposed to multiple stresses at the same time, a combinatorial approach reflecting real-world scenarios, show tailored responses completely different from the response to the individual stresses, due to the stress-related plasticity of plant genome and to specific metabolic modifications. In this view, recently it has been found that γ-aminobutyric acid (GABA) but not glycine betaine (GB) is accumulated in durum wheat plants under salinity only when it is combined with high nitrate and high light.

INTRODUCTION

THE NATURE OF GABA ACCUMULATION IS STILL A CONTROVERSIAL ISSUE

Findings

CONCLUSION