Department of Horticultural Sciences, Texas A&M University, College station, TX 77843, USA.
Present address: USDA-ARS, Agroecosystem Management Research, Lincoln, NE, 68503, USA.
BMC Plant Biol. 2022 Mar 30;22(1):156. doi: 10.1186/s12870-022-03505-z.
The tomato psyllid, Bactericera cockerelli Šulc (Hemiptera: Triozidae), is a pest of solanaceous crops such as tomato (Solanum lycopersicum L.) in the U.S. and vectors the disease-causing pathogen 'Candidatus Liberibacter solanacearum' (or Lso). Disease symptom severity is dependent on Lso haplotype: tomato plants infected with Lso haplotype B experience more severe symptoms and higher mortality compared to plants infected with Lso haplotype A. By characterizing the molecular differences in the tomato plant's responses to Lso haplotypes, the key components of LsoB virulence can be identified and, thus, targeted for disease mitigation strategies.
To characterize the tomato plant genes putatively involved in the differential immune responses to Lso haplotypes A and B, RNA was extracted from tomato 'Moneymaker' leaves 3 weeks after psyllid infestation. Gene expression levels were compared between uninfected tomato plants (i.e., controls and plants infested with Lso-free psyllids) and infected plants (i.e., plants infested with psyllids infected with either Lso haplotype A or Lso haplotype B). Furthermore, expression levels were compared between plants infected with Lso haplotype A and plants infected with Lso haplotype B. A whole transcriptome analysis identified 578 differentially expressed genes (DEGs) between uninfected and infected plants as well as 451 DEGs between LsoA- and LsoB-infected plants. These DEGs were primarily associated with plant defense against abiotic and biotic stressors, growth/development, plant primary metabolism, transport and signaling, and transcription/translation. These gene expression changes suggested that tomato plants traded off plant growth and homeostasis for improved defense against pathogens, especially when infected with LsoB. Consistent with these results, tomato plant growth experiments determined that LsoB-infected plants were significantly stunted and had impaired negative geotropism. However, it appeared that the defense responses mounted by tomatoes were insufficient for overcoming the disease symptoms and mortality caused by LsoB infection, while these defenses could compensate for LsoA infection.
The transcriptomic analysis and growth experiments demonstrated that Lso-infected tomato plants underwent gene expression changes related to abiotic and biotic stressors, impaired growth/development, impaired plant primary metabolism, impaired transport and signaling transduction, and impaired transcription/translation. Furthermore, the transcriptomic analysis also showed that LsoB-infected plants, relative to LsoA-infected, experienced more severe stunting, had improved responses to some stressors and impaired responses to others, had poorer transport and signaling transduction, and had impaired carbohydrate synthesis and photosynthesis.
番茄斑潜蝇，Bactericera cockerelli Šulc（半翅目：瘿蚊科），是美国番茄（Solanum lycopersicum L.）等茄科作物的害虫，也是致病病原体“候选利夫利伯菌 solanacearum”（或 Lso）的传播媒介。疾病症状的严重程度取决于 Lso 单倍型：感染 Lso 单倍型 B 的番茄植物比感染 Lso 单倍型 A 的植物经历更严重的症状和更高的死亡率。通过描述番茄植物对 Lso 单倍型的分子差异反应，可以确定 LsoB 毒力的关键组成部分，并因此针对疾病缓解策略进行靶向。
为了描述番茄植物对 Lso 单倍型 A 和 B 的免疫反应差异的推定基因，从感染斑潜蝇后 3 周的番茄“Moneymaker”叶片中提取 RNA。比较了未感染番茄植物（即对照和感染无 Lso 斑潜蝇的植物）和感染植物（即感染 Lso 单倍型 A 或 Lso 单倍型 B 的斑潜蝇感染的植物）之间的基因表达水平。此外，还比较了感染 Lso 单倍型 A 的植物和感染 Lso 单倍型 B 的植物之间的表达水平。全转录组分析确定了 578 个差异表达基因（DEGs），这些基因在未感染和感染植物之间以及 LsoA-和 LsoB 感染植物之间表达。这些 DEGs 主要与植物对非生物和生物胁迫、生长/发育、植物初级代谢、运输和信号转导以及转录/翻译的防御有关。这些基因表达的变化表明，番茄植物为了提高对病原体的防御能力，牺牲了植物的生长和内稳态。与这些结果一致，番茄植物生长实验表明，LsoB 感染的植物明显矮小，负向地性受损。然而，似乎番茄所产生的防御反应不足以克服由 LsoB 感染引起的疾病症状和死亡率，而这些防御反应可以弥补 LsoA 感染的影响。
转录组分析和生长实验表明，Lso 感染的番茄植物经历了与非生物和生物胁迫、生长/发育受损、植物初级代谢受损、运输和信号转导受损以及转录/翻译受损相关的基因表达变化。此外，转录组分析还表明，与 LsoA 感染相比，LsoB 感染的植物生长更严重，对一些胁迫的反应更好，对另一些胁迫的反应更差，运输和信号转导能力更差，碳水化合物合成和光合作用能力更差。
