Sun Yue, Shao Xiaolong, Zhang Yingchao, Han Liangliang, Huang Jiadai, Xie Yingpeng, Liu Jingui, Deng Xin
Department of Biomedical Sciences, City University of Hong Kong, Kowloon Tong, Hong Kong SAR, China.
College of Plant Protection, Laboratory of Plant Immunity, Key Laboratory of Integrated Management of Crop Diseases and Pests, Nanjing Agricultural University, No. 1 Weigang, Nanjing, 210095, Jiangsu, China.
Cell Biosci. 2022 Sep 5;12(1):147. doi: 10.1186/s13578-022-00884-6.
Sufficient nutrition contributes to rapid translational elongation and protein synthesis in eukaryotic cells and prokaryotic bacteria. Fast synthesis and accumulation of type III secretion system (T3SS) proteins conduce to the invasion of pathogenic bacteria into the host cells. However, the translational elongation patterns of T3SS proteins in pathogenic bacteria under T3SS-inducing conditions remain unclear. Here, we report a mechanism of translational elongation of T3SS regulators, effectors and structural protein in four model pathogenic bacteria (Pseudomonas syringae, Pseudomonas aeruginosa, Xanthomonas oryzae and Ralstonia solanacearum) and a clinical isolate (Pseudomonas aeruginosa UCBPP-PA14) under nutrient-limiting conditions. We proposed a luminescence reporter system to quantitatively determine the translational elongation rates (ERs) of T3SS regulators, effectors and structural protein under different nutrient-limiting conditions and culture durations.
The translational ERs of T3SS regulators, effectors and structural protein in these pathogenic bacteria were negatively regulated by the nutrient concentration and culture duration. The translational ERs in 0.5× T3SS-inducing medium were the highest of all tested media. In 1× T3SS-inducing medium, the translational ERs were highest at 0 min and then rapidly decreased. The translational ERs of T3SS regulators, effectors and structural protein were inhibited by tRNA degradation and by reduced levels of elongation factors (EFs).
Rapid translational ER and synthesis of T3SS protein need adequate tRNAs and EFs in nutrient-limiting conditions. Numeric presentation of T3SS translation visually indicates the invasion of bacteria and provides new insights into T3SS expression that can be applied to other pathogenic bacteria.
充足的营养有助于真核细胞和原核细菌中的翻译延伸和蛋白质合成。III型分泌系统（T3SS）蛋白的快速合成和积累有助于病原菌侵入宿主细胞。然而，在T3SS诱导条件下病原菌中T3SS蛋白的翻译延伸模式仍不清楚。在此，我们报道了四种模式病原菌（丁香假单胞菌、铜绿假单胞菌、水稻白叶枯菌和青枯雷尔氏菌）和一株临床分离株（铜绿假单胞菌UCBPP-PA14）在营养限制条件下T3SS调节蛋白、效应蛋白和结构蛋白的翻译延伸机制。我们提出了一种发光报告系统，以定量测定不同营养限制条件和培养时间下T3SS调节蛋白、效应蛋白和结构蛋白的翻译延伸率（ERs）。
这些病原菌中T3SS调节蛋白、效应蛋白和结构蛋白的翻译ERs受营养浓度和培养时间的负调控。在所有测试培养基中，0.5×T3SS诱导培养基中的翻译ERs最高。在1×T3SS诱导培养基中，翻译ERs在0分钟时最高，然后迅速下降。T3SS调节蛋白、效应蛋白和结构蛋白的翻译ERs受到tRNA降解和延伸因子（EFs）水平降低的抑制。
在营养限制条件下，T3SS蛋白的快速翻译ER和合成需要足够的tRNA和EFs。T3SS翻译的数值呈现直观地表明了细菌的侵袭，并为T3SS表达提供了新的见解，可应用于其他病原菌。
