Abstract
BackgroundDrought is a major constraint for plant growth and crop productivity that is receiving an increased attention due to global climate changes. Chloroplasts act as environmental sensors, however, only partial information is available on stress-induced mechanisms within plastids. Here, we investigated the chloroplast response to a severe drought treatment and a subsequent recovery cycle in tomato through physiological, metabolite and proteomic analyses.ResultsUnder stress conditions, tomato plants showed stunted growth, and elevated levels of proline, abscisic acid (ABA) and late embryogenesis abundant gene transcript. Proteomics revealed that water deficit deeply affects chloroplast protein repertoire (31 differentially represented components), mainly involving energy-related functional species. Following the rewatering cycle, physiological parameters and metabolite levels indicated a recovery of tomato plant functions, while proteomics revealed a still ongoing adjustment of the chloroplast protein repertoire, which was even wider than during the drought phase (54 components differentially represented). Changes in gene expression of candidate genes and accumulation of ABA suggested the activation under stress of a specific chloroplast-to-nucleus (retrograde) signaling pathway and interconnection with the ABA-dependent network.ConclusionsOur results give an original overview on the role of chloroplast as enviromental sensor by both coordinating the expression of nuclear-encoded plastid-localised proteins and mediating plant stress response. Although our data suggest the activation of a specific retrograde signaling pathway and interconnection with ABA signaling network in tomato, the involvement and fine regulation of such pathway need to be further investigated through the development and characterization of ad hoc designed plant mutants.
Highlights
Drought is a major constraint for plant growth and crop productivity that is receiving an increased attention due to global climate changes
Morphological, physiological and biochemical responses to drought stress A long-term drought treatment was applied to tomato plants by water withholding for 19 days followed by a rewatering phase
Our results effectively provide an original overview on the chloroplast response to long-term drought stress and subsequent recovery in tomato
Summary
Drought is a major constraint for plant growth and crop productivity that is receiving an increased attention due to global climate changes. Chloroplasts act as environmental sensors, only partial information is available on stress-induced mechanisms within plastids. Chloroplast is a semi-autonomous organelle since most plastid-localised proteins are nuclearencoded This implicates the existence of sophisticated communication mechanisms that allow adequate coordination of gene expression in both organelles, ensuring a correct functioning of overall cellular metabolism [3, 7,8,9]. Chloroplast harbours many cellular vital processes (i.e., aromatic amino acids, fatty acids and carotenoids biosynthesis and sulphate assimilation pathways) in Tamburino et al BMC Plant Biology (2017) 17:40 addition to photosynthesis, and is considered a key element in plant stress response, because it acts as sensor of environmental changes optimizing different cell functions for triggering the adaptive response to stressful conditions. Several aspects of plastid alterations following water deficit are still poorly characterized
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