Effect on tomato plants of asymptomatic infection with southern tomato virus

Southern tomato virus (STV) often infects healthy tomato plants (Solanum lycopersicum). In this study, we compared STV-free and STV-infected cultivar M82 plants to determine the effect of STV infection on the host plant. STV-free plants exhibited a short and bushy phenotype, whereas STV-infected plants exhibited increased height. STV-infected plants produced more fruit than STV-free plants, and the germination rate of seeds from STV-infected plants was higher than that of seeds from STV-free plants. This phenotypic difference was also observed in progeny plants (siblings) derived from a single STV-infected plant in which the transmission rate of STV to progeny plants via the seeds was approximately 86%. These results suggest that the interaction between STV and host plants is mutualistic. Transcriptome analyses revealed that STV infection affected gene expressions in host plants, notably evidenced by down-regulation of genes involved in ethylene biosynthesis and signaling. STV-infected tomato plants thus might be artificially selected due to their superior traits as a crop. Overall design: RNA-seq analyses using three 1-month-old STV-infected and three 1-month-old STV-free tomato plants of cv. M82

南方番茄病毒（Southern tomato virus, STV）常侵染健康番茄（Solanum lycopersicum）植株。本研究以STV未侵染与STV侵染的M82栽培番茄为材料，探究该病毒侵染对寄主植物的影响。未侵染STV的植株呈现矮化丛生表型，而STV侵染植株的株高显著增加；侵染植株的单株挂果量高于未侵染植株，且其种子的发芽率亦显著高于未侵染植株的种子。该表型差异在单株STV侵染植株的后代植株（姊妹株）中同样存在，且STV通过种子向子代植株的传播率约为86%。上述结果表明，南方番茄病毒与寄主植物之间存在互利共生关系。转录组分析显示，STV侵染会调控寄主植物的基因表达，其中尤以乙烯生物合成与信号通路相关基因的下调表达最为显著。因此，作为栽培作物，STV侵染的番茄植株因其优良性状可能被人工选育。实验整体设计：以3株1月龄STV侵染与3株1月龄未侵染的M82栽培番茄为材料开展RNA-seq分析。