Integrated Transcriptomic and Proteomic Analysis of the Global Response of Synechococcus to High Light Stress*[S

Qian Xiong,Jie Feng,Si-Ting Li,Gui-Ying Zhang,Zhi-Xian Qiao,Zhuo Chen,Ying Wu,Yan Lin,Tao Li,Feng Ge,Jin-Dong Zhao

doi:10.1074/mcp.m114.046003

Abstract

Sufficient light is essential for the growth and physiological functions of photosynthetic organisms, but prolonged exposure to high light (HL) stress can cause cellular damage and ultimately result in the death of these organisms. Synechococcus sp. PCC 7002 (hereafter Synechococcus 7002) is a unicellular cyanobacterium with exceptional tolerance to HL intensities. However, the molecular mechanisms involved in HL response by Synechococcus 7002 are not well understood. Here, an integrated RNA sequencing transcriptomic and quantitative proteomic analysis was performed to investigate the cellular response to HL in Synechococcus 7002. A total of 526 transcripts and 233 proteins were identified to be differentially regulated under HL stress. Data analysis revealed major changes in mRNAs and proteins involved in the photosynthesis pathways, resistance to light-induced damage, DNA replication and repair, and energy metabolism. A set of differentially expressed mRNAs and proteins were validated by quantitative RT-PCR and Western blot, respectively. Twelve genes differentially regulated under HL stress were selected for knockout generation and growth analysis of these mutants led to the identification of key genes involved in the response of HL in Synechococcus 7002. Taken altogether, this study established a model for global response mechanisms to HL in Synechococcus 7002 and may be valuable for further studies addressing HL resistance in photosynthetic organisms.

Highlights

Cyanobacteria are a large group of prokaryotes that have photosystem II (PS II)1, photosystem I (PS I), and carry out
Most of the cyanobacteria cannot tolerate a light intensity of 1000 ␮mol photons/m2/s, Synechococcus 7002 can grow rapidly at a light intensity of 2000 ␮mol photons/m2/s, making it a very nice organism to study the mechanisms of acclimation to high-light (HL)
To analyze the molecular components and regulatory mechanisms of HL-acclimation networks, especially for genes/proteins involved in long-term acclimation, we studied transcription and translation of Synechococcus 7002 in response to HL conditions with methods coupling RNA sequencing (RNA-Seq) and mass spectrometry

Summary

Introduction

Cyanobacteria are a large group of prokaryotes that have photosystem II (PS II)1, photosystem I (PS I), and carry out. To analyze the molecular components and regulatory mechanisms of HL-acclimation networks, especially for genes/proteins involved in long-term acclimation, we studied transcription and translation of Synechococcus 7002 in response to HL conditions with methods coupling RNA sequencing (RNA-Seq) and mass spectrometry. Comparison of Transcriptome and Proteome Data—To estimate the reproducibility of the TMT-based quantitative proteomic and RNA-Seq results, linear regression analysis based on the log2-transformed protein ratios or gene coverage depth was performed for pair-wise comparison of the two experiment replicates.

Results

Conclusion