Abstract
BackgroundDrought stress during grain development causes significant yield loss in cereal production. The phosphorylated modification of starch granule-binding proteins (SGBPs) is an important mechanism regulating wheat starch biosynthesis. In this study, we performed the first proteomics and phosphoproteomics analyses of SGBPs in elite Chinese bread wheat (Triticum aestivum L.) cultivar Jingdong 17 under well-watered and water-stress conditions.ResultsWater stress treatment caused significant reductions in spike grain numbers and weight, total starch and amylopectin content, and grain yield. Two-dimensional gel electrophoresis revealed that the quantity of SGBPs was reduced significantly by water-deficit treatment. Phosphoproteome characterization of SGBPs under water-deficit treatment demonstrated a reduced level of phosphorylation of main starch synthesis enzymes, particularly for granule-bound starch synthase (GBSS I), starch synthase II-a (SS II-a), and starch synthase III (SS III). Specifically, the Ser34 site of the GBSSI protein, the Tyr358 site of SS II-a, and the Ser837 site of SS III-a exhibited significant less phosphorylation under water-deficit treatment than well-watered treatment. Furthermore, the expression levels of several key genes related with starch biosynthesis detected by qRT-PCR were decreased significantly at 15 days post-anthesis under water-deficit treatment. Immunolocalization showed a clear movement of GBSS I from the periphery to the interior of starch granules during grain development, under both water-deficit and well-watered conditions.ConclusionsOur results demonstrated that the reduction in gene expression or transcription level, protein expression and phosphorylation levels of starch biosynthesis related enzymes under water-deficit conditions is responsible for the significant decrease in total starch content and grain yield.
Highlights
Drought stress during grain development causes significant yield loss in cereal production
Our results revealed the changes of starch granule-binding proteins (SGBPs) phosphorylation level in vivo in response to drought stress, as well as starch biosynthesis, which provides new insights into the molecular mechanisms of the response to drought stress
SGBPs were subjected to large-scale phosphoproteome analysis with TiO2 microcolumns enrichment and LC-MS/MS, and we studied phosphorylated SGBPs that regulate starch biosynthesis and drought stress responses
Summary
Drought stress during grain development causes significant yield loss in cereal production. Wheat (Triticum aestivum L.) grain yield and quality are affected by many environmental factors. Water-deficit is one of the most important stress factor, as it causes significant yield loss in cereal production [1, 2]. Starch consists of the glucose polymers amylose and amylopectin. Amylopectin consists mainly of long chains of (1–4)-linked D-glucopyranosyl units with occasional branching (1–6) linkages, resulting in tandem linked clusters (~9–10 nm long each) [7, 8]. ADP-glucose pyrophosphorylase (AGPase), SS, Chen et al BMC Plant Biology (2017) 17:168 starch-branching enzyme (SBE), and starch-debranching enzyme (DBE) are involved in amylopectin synthesis [9]
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