Transcriptomic and proteomic analyses of a pale-green durum wheat mutant shows variations in photosystem components and metabolic deficiencies under drought stress

Ariadna Peremarti,Luigi Cattivelli,Alessio Aprile,Enrica Roncaglia,Caterina Marè,Dolors Villegas,Conxita Royo

doi:10.1186/1471-2164-15-125

Abstract

BackgroundLeaf pigment content is an important trait involved in environmental interactions. In order to determine its impact on drought tolerance in wheat, we characterized a pale-green durum wheat mutant (Triticum turgidum L. var. durum) under contrasting water availability conditions.ResultsThe pale-green mutant was investigated by comparing pigment content and gene/protein expression profiles to wild-type plants at anthesis. Under well-watered (control) conditions the mutant had lower levels of chlorophylls and carotenoids, but higher levels of xanthophyll de-epoxidation compared to wild-type. Transcriptomic analysis under control conditions showed that defense genes (encoding e.g. pathogenesis-related proteins, peroxidases and chitinases) were upregulated in the mutant, suggesting the presence of mild oxidative stress that was compensated without altering the net rate of photosynthesis. Transcriptomic analysis under terminal water stress conditions, revealed the modulation of antioxidant enzymes, photosystem components, and enzymes representing carbohydrate metabolism and the tricarboxylic acid cycle, indicating that the mutant was exposed to greater oxidative stress than the wild-type plants, but had a limited capacity to respond. We also compared the two genotypes under irrigated and rain-fed field conditions over three years, finding that the greater oxidative stress and corresponding molecular changes in the pale-green mutant were associated to a yield reduction.ConclusionsThis study provides insight on the effect of pigment content in the molecular response to drought. Identified genes differentially expressed under terminal water stress may be valuable for further studies addressing drought resistance in wheat.

Highlights

Leaf pigment content is an important trait involved in environmental interactions
Chloroplast ultrastructure Wild-type and mutant leaf sections at the tillering stage were compared by transmission electron microscopy (TEM)
Under well-watered glasshouse conditions the reduced chlorophyll and carotenoids content of our pale-green mutant resulted on mild oxidative stress symptoms that could be compensated without altering photosynthesis and physiological performance by the induction of stressresponse genes

Summary

Introduction

Leaf pigment content is an important trait involved in environmental interactions. In order to determine its impact on drought tolerance in wheat, we characterized a pale-green durum wheat mutant (Triticum turgidum L. var. durum) under contrasting water availability conditions. Plants typically respond to water stress by reducing the leaf chlorophyll content, and their photosynthetic activity [2]. Thylakoid organization is coordinated with the expression of nuclear genes, encoding pigment-binding proteins that are imported into the chloroplast to assemble the photosynthetic complexes and the expression of chloroplast encoded genes [8,9]. This process is tightly regulated, so mutants deficient in chlorophyll content can arise through the disruption of chlorophyll biosynthesis and via processes related to photosystem assembly and light-harvesting activity [10,11]. Such chlorophyll mutants have been used to study the function of photosynthetic components as described in rice e.g. [12,13], barley e.g. [14,15,16,17] and wheat e.g. [18,19,20]

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