Data_Sheet_1_Comparative Transcriptome Analysis Reveals the Biocontrol Mechanism of Bacillus velezensis F21 Against Fusarium Wilt on Watermelon.docx

The watermelon (Citrullus lanatus) is one of the most important horticultural crops for fruit production worldwide. However, the production of watermelon is seriously restricted by one kind of soilborne disease, Fusarium wilt, which is caused by Fusarium oxysporum f. sp. niveum (Fon). In this study, we identified an efficient PGPR strain B. velezensis F21, which could be used in watermelon production for Fon control. The results of biocontrol mechanisms showed that B. velezensis F21 could suppress the growth and spore germination of Fon in vitro. Moreover, B. velezensis F21 could also enhance plant basal immunity to Fon by increasing the expression of plant defense related genes and activities of some defense enzymes, such as CAT, POD, and SOD. To elucidate the detailed mechanisms regulating B. velezensis F21 biocontrol of Fusarium wilt in watermelon, a comparative transcriptome analysis using watermelon plant roots treated with B. velezensis F21 or sterile water alone and in combination with Fon inoculation was conducted. The transcriptome sequencing results revealed almost one thousand ripening-related differentially expressed genes (DEGs) in the process of B. velezensis F21 triggering ISR (induced systemic resistance) to Fon. In addition, the Gene Ontology (GO) classification and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment indicated that numerous of transcription factors (TFs) and plant disease resistance genes were activated and validated by using quantitative real-time PCR (qRT-PCR), which showed significant differences in expression levels in the roots of watermelon with different treatments. In addition, genes involved in the MAPK signaling pathway and phytohormone signaling pathway were analyzed, and the results indicated that B. velezensis F21 could enhance plant disease resistance to Fon through the above related genes and phytohormone signal factors. Taken together, this study substantially expands transcriptome data resources and suggests a molecular framework for B. velezensis F21 inducing systemic resistance to Fon in watermelon. In addition, it also provides an effective strategy for the control of Fusarium wilt in watermelon.

西瓜（Citrullus lanatus）是全球果品生产中至关重要的园艺作物之一。然而，西瓜的产业生产却受到由尖孢镰刀菌西瓜专化型（Fusarium oxysporum f. sp. niveum，Fon）引发的土传枯萎病的严重制约。本研究筛选得到一株高效的植物根际促生菌（Plant Growth Promoting Rhizobacteria, PGPR）——贝莱斯芽孢杆菌（Bacillus velezensis）F21，该菌株可应用于西瓜生产以防治Fon。生物防控机制研究结果显示，贝莱斯芽孢杆菌F21在体外可抑制Fon的生长与孢子萌发。此外，该菌株还可通过上调植物防御相关基因的表达水平，以及提升过氧化氢酶（CAT）、过氧化物酶（POD）、超氧化物歧化酶（SOD）等防御酶的活性，增强植株对Fon的基础免疫能力。为阐明贝莱斯芽孢杆菌F21防控西瓜枯萎病的具体分子机制，本研究对分别经贝莱斯芽孢杆菌F21、无菌水处理，以及联合Fon接种处理的西瓜根系样本开展了比较转录组学分析。转录组测序结果表明，在贝莱斯芽孢杆菌F21诱导植株对Fon产生系统诱导抗性（Induced Systemic Resistance, ISR）的过程中，共鉴定得到近千个与抗病相关的差异表达基因（Differentially Expressed Genes, DEGs）。此外，基因本体（Gene Ontology, GO）功能分类与京都基因与基因组百科全书（Kyoto Encyclopedia of Genes and Genomes, KEGG）通路富集分析结果显示，大量转录因子（Transcription Factors, TFs）与植物抗病基因被激活，并通过实时荧光定量PCR（quantitative real-time PCR, qRT-PCR）进行了验证，不同处理组的西瓜根系中这些基因的表达量存在显著差异。本研究还对丝裂原活化蛋白激酶（Mitogen-Activated Protein Kinase, MAPK）信号通路及植物激素信号通路相关基因进行了分析，结果证实贝莱斯芽孢杆菌F21可通过上述相关基因与植物激素信号因子提升植株对Fon的抗病能力。综上，本研究极大丰富了西瓜转录组数据资源，并为贝莱斯芽孢杆菌F21诱导西瓜植株对Fon产生系统抗性提供了分子调控框架参考。同时，本研究也为西瓜枯萎病的防控提供了一种高效可行的策略。