Global RNA sequencing reveals enhanced photosynthetic activity and auxin response in Brassica napus treated with Pseudomonas chlororaphis PA23

Plant growth promoting bacteria (PGPB) are a growing subset of agricultural adjuncts which can be used to increase crop yield and plant productivity. Although, substantial research has been conducted on the metabolites and active molecules secreted by PGPBs; relatively little is known about their effects on the global transcriptome of the host plant. The present study was carried out to investigate changes in the gene expression landscape of early vegetative Brassica napus following treatment with Pseudomonas chlororaphis PA23. This PGPB was isolated from the soybean rhizosphere and has been extensively studied as a biocontrol agent. However, little is known about its effects on plant growth and development. Using a combination of RNA-sequencing and physiological analyses, we identified increased abundance of mRNA transcripts associated with photosynthesis and phytohormone response. Phenotypically we observed increased photosynthetic rates and larger root and shoot systems in B. napus following P. chlororaphis PA23 treatment. Lastly, we identified auxin production by P. chlororaphis PA23 which likely contributes to changes in gene expression and observed phenotypic differences in root and shoot structures. Together, the results of our study suggest that PA23 is a potent plant growth promoting agent with the potential for field applications as an agricultural adjunct. Overall design: Total of 8 samples: 2 time points (24hour and 7days) 2 tissue types (shoot and root) 2 replicates of each sample

植物促生细菌（Plant growth promoting bacteria, PGPB）是一类日益受到关注的农业辅助制剂，可用于提升作物产量与植物生长效能。尽管学界已针对PGPB分泌的代谢产物与活性分子开展了大量研究，但目前对其如何影响宿主植物的全球转录组仍知之甚少。
本研究旨在探究嗜氯假单胞菌（Pseudomonas chlororaphis）PA23处理后，早期营养生长期甘蓝型油菜（Brassica napus）的基因表达谱变化。该PGPB分离自大豆根际，作为生防菌剂已被广泛研究，但目前对其促进植物生长发育的具体效应仍鲜有报道。
本研究结合RNA测序（RNA-sequencing）与生理分析手段，发现与光合作用及植物激素响应相关的mRNA转录本丰度显著上调。表型层面观察到，经PA23处理的甘蓝型油菜光合速率提升，根系与地上部更为发达。此外，本研究证实PA23可产生生长素（auxin），这大概率是其调控植物基因表达变化、改变根系与地上部结构表型的核心诱因。
综合来看，本研究结果表明PA23是一种高效的植物促生制剂，具备作为农业辅助制剂开展田间应用的潜力。
实验整体设计：本研究共设置8个样本，涵盖2个时间点（24小时与7天）、2种组织类型（地上部与根系），每组样本设置2次重复。