Abstract
BackgroundRice is a major crop worldwide. Bacterial blight (BB) caused by Xanthomonas oryzae pv. oryzae (Xoo) has become one of the most devastating diseases for rice. It has been clear that phosphorylation plays essential roles in plant disease resistance. However, the role of phosphorylation is poorly understood in rice-Xoo system. Here, we report the first study on large scale enrichment of phosphopeptides and identification of phosphosites in rice before and 24 h after Xoo infection.ResultsWe have successfully identified 2367 and 2223 phosphosites on 1334 and 1297 representative proteins in 0 h and 24 h after Xoo infection, respectively. A total of 762 differentially phosphorylated proteins, including transcription factors, kinases, epi-genetic controlling factors and many well-known disease resistant proteins, are identified after Xoo infection suggesting that they may be functionally relevant to Xoo resistance. In particular, we found that phosphorylation/dephosphorylation might be a key switch turning on/off many epi-genetic controlling factors, including HDT701, in response to Xoo infection, suggesting that phosphorylation switch overriding the epi-genetic regulation may be a very universal model in the plant disease resistance pathway.ConclusionsThe phosphosites identified in this study would be a big complementation to our current knowledge in the phosphorylation status and sites of rice proteins. This research represents a substantial advance in understanding the rice phosphoproteome as well as the mechanism of rice bacterial blight resistance.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0541-2) contains supplementary material, which is available to authorized users.
Highlights
Phosphorylation dynamics of rice variety IRBB5 in response to Xanthomonas oryzae pv. oryzae (Xoo) infection A Bacterial blight (BB) resistant variety IRBB5 was used as the starting material in this study due to its good performance against BB (Fig. 1a and b)
Our infection assay found that the lesion area of IRBB5 was only around 7 % when the Xoo strain zhe173 was inoculated for 10 days, while IRBB13, a BB susceptible variety, showed over 35 % lesion area under the same condition (Fig. 1c), suggesting IRBB5 is highly resistant to BB
In this study, a quantitative, MS-based, label-free proteomic analysis identified 2450 non-redundant phosphopeptides from 1302 phosphoproteins of rice at both 0 h and 24 h after Xoo infection including 762 differentially phosphorylated proteins, representing the first phosphoproteomic attempt to explore the phosphorylation events in rice- signaling of rice-Xoo interaction is a very complex event pathogen cross-talk
Summary
Oryzae (Xoo) has become one of the most devastating diseases for rice. It has been clear that phosphorylation plays essential roles in plant disease resistance. The role of phosphorylation is poorly understood in rice-Xoo system. We report the first study on large scale enrichment of phosphopeptides and identification of phosphosites in rice before and 24 h after Xoo infection. The recognition of effector proteins and signal transduction in the second defense are of great importance in the plant-pathogen interaction study. Recent studies have revealed that besides the quantity of protein synthesis, post-translational modification (PTM) of the pre-existing signaling proteins is critical in the signal transduction cascade to ensure that plants respond to the pathogen invasion in a prompt manner [1]. It was suggested that more than one-third of all proteins are potentially phosphorylated [3]
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