Abstract
To better understand abscisic acid (ABA) regulation of the synthesis of chloroplast proteins in maize (Zea mays L.) in response to drought and light, we compared leaf proteome differences between maize ABA-deficient mutant vp5 and corresponding wild-type Vp5 green and etiolated seedlings exposed to drought stress. Proteins extracted from the leaves of Vp5 and vp5 seedlings were used for two-dimensional electrophoresis (2-DE) and subsequent matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS). After Coomassie brilliant blue staining, approximately 450 protein spots were reproducibly detected on 2-DE gels. A total of 36 differentially expressed protein spots in response to drought and light were identified using MALDI-TOF MS and their subcellular localization was determined based on the annotation of reviewed accession in UniProt Knowledgebase and the software prediction. As a result, corresponding 13 proteins of the 24 differentially expressed protein spots were definitely localized in chloroplasts and their expression was in an ABA-dependent way, including 6 up-regulated by both drought and light, 5 up-regulated by drought but down-regulated by light, 5 up-regulated by light but down-regulated by drought; 5 proteins down-regulated by drought were mainly those involved in photosynthesis and ATP synthesis. Thus, the results in the present study supported the vital role of ABA in regulating the synthesis of drought- and/or light-induced proteins in maize chloroplasts and would facilitate the functional characterization of ABA-induced chloroplast proteins in C4 plants.
Highlights
The biogenesis of plastids is regulated by external and internal factors, light and phytohormones, such as abscisic acid (ABA) [1,2,3]
Previous reports have shown that some chloroplast proteins, such as the light-harvesting chlorophyll a/b binding proteins and chloroplastic antioxidant defense enzymes, are involved in ABA signal transduction and play a positive role in the response to ABA [3,7,8]
Under dim light, Vp5 and vp5 leaves had comparable chlorophyll contents (Figure 3). These results indicated that light and ABA are the major factors affecting chlorophyll synthesis, while drought has a limited negative effect on chlorophyll synthesis
Summary
The biogenesis of plastids is regulated by external and internal factors, light and phytohormones, such as abscisic acid (ABA) [1,2,3]. ABA signal transduction has been extensively studied, and numerous signaling components have been identified, including the chloroplast envelope-localized ABA receptor [6]. Previous reports have shown that some chloroplast proteins, such as the light-harvesting chlorophyll a/b binding proteins and chloroplastic antioxidant defense enzymes, are involved in ABA signal transduction and play a positive role in the response to ABA [3,7,8]. The expression of chloroplast proteins and chlorophyll synthesis are significantly affected in crop plant responses to drought [10]. Many proteins regulated by light have been identified through proteome analysis in green and etiolated maize seedlings [2,11]. Few comparative proteomic studies have addressed the effect of ABA on the drought- and light-regulation of chloroplast proteins
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