西瓜噬酸菌不同菌株与甜瓜幼苗早期互作的转录组学分析

Transcriptomic analysis of early interaction between melon seedlings and Acidovorax citrulli strains

西瓜噬酸菌(Acidovorax citrulli)引起的瓜类细菌性果斑病(bacterial fruit blotch,BFB)是西瓜、甜瓜等葫芦科作物上毁灭性种传病害。本文利用RNA-seq技术,分析了2个西瓜噬酸菌菌株(pslb65和AAC00-1)分别诱导甜瓜感病品种IVF667幼苗6 h和12 h后的基因表达谱。结果表明,这2个菌株侵染寄主6 h后,分别检测到1 029和3 561个差异表达基因,其中上调基因分别为355和1 621个,下调基因分别为674和1 940个;与寄主互作12 h后,差异基因分别有2 397和1 875个,上调基因分别为903和898个,下调基因分别为1 494和977个。GO功能注释发现,pslb65与甜瓜幼苗互作的差异基因显著富集在生物学过程中的发育和代谢2个亚类,所占比例分别为32.92%和35.36%。在分子功能中转录因子所占比例较大,达到67.65%;AAC00-1与甜瓜幼苗互作后,差异基因显著富集在生物学过程中的转运和定位中,比例分别为23.84%和24.18%。在分子功能中氧化还原酶活性亚类所占比例高达17.59%。西瓜噬酸菌pslb65和AAC00-1侵染寄主6 h,Rboh、CaMCML、CDPK和FLS2等编码基因在植物-病原互作途径(csv04626)多为下调表达,植物-病原互作途径被抑制;12 h,pslb65-甜瓜互作途径相关基因多下调,AAC00-1-甜瓜互作途径相关基因多上调,推测此时植物-病原互作途径被AAC00-1激活,引起寄主的防御反应。西瓜噬酸菌pslb65和AAC00-1均可诱导植物发病,但在引起植物感病途径上略有不同,这可能与它们来自西瓜噬酸菌的不同亚群有关。最后,选取pslb65与寄主互作途径的6个基因进行qRT-PCR验证,结果与转录组测序结果基本一致。本研究初步揭示了西瓜噬酸菌2个不同菌株与寄主互作在转录水平上的表达差异,为研究甜瓜与不同菌株的互作机制差异奠定了基础。

Bacterial fruit blotch （BFB） caused by Acidovorax citrulli is considered as one of the most destructive seed borne diseases of cucurbitaceous plants such as watermelon and melon. In this study, RNA seq technology was applied to reveal transcriptome of susceptible melon IVF667 seedlings triggered by A.citrulli strains pslb65 or AAC00 1 at 6 h and 12 h post inoculation. Of the total 1 029 or 3 561 differentially expressed genes （DEGs） identified at 6 h in IVF667 after inoculation with pslb65 or AAC00 1, there were 355 or 1 621 up regulated, and 674 or 1 940 down regulated DEGs, respectively; While out of 2 397 or 1 875 DEGs at 12 h after infected with pslb65 or AAC00 1, there were 903 or 898 up regulated genes, and 1 494 or 977 down regulated genes, respectively. Gene ontology analysis of DEGs involved in melon pslb65 interaction revealed that most of the DEGs in the biological process belonged to “cellular development” and “metabolism” categories, accounting for 32.92% and 35.36%, respectively. Most of the DEGs （67.65%） in the molecular function category were predicted to be transcription factors. While for the DEGs involved in melon AAC00 1 interaction, transportation and localization were the most enriched biological process categories, and oxidoreductase activity was the most enriched molecular function category, accounting for 23.84%, 24.18%, and 17.59%, respectively. Analysis of plant pathogen interaction pathway showed that genes coding Rboh, CaMCML, CDPK and FLS2 were down regulated at 6 h post inoculation of pslb65 and AAC00 1, suggesting that the corresponding pathway was suppressed; These genes were down regulated and up regulated at 12 h post inoculation with pslb65 and AAC00 1, respectively, indicating that defense pathways of melon seedlings might be activated by AAC00 1. Differences in susceptibility of melon to these two A.citrulli strains might be attributed to the fact that pslb65 and AAC00 1 come from different subgroup. Further expression levels of validation for six genes in melon pslb65 interaction using qRT PCR were consistent with that in the Illumina sequencing results. This is the first transcriptome analysis of melon seedlings infected by A. citrulli strains from two distinct groups, which will provide a foundation for further characterization of the compatible interaction between melon and A.citrulli.