Comparative performance and transcriptomics of tomato (Solanum lycopersicum) in response to Bombus terrestris (Hymenoptera, Apidae) and 2,4-dichlorophenoxyacetic acid

The introduction of pollinator bumblebees (Bombus terrestris) or using the plant hormone, 2,4-dichlorophenoxyacetic acid (2,4-D), are common methods to improve tomato production in greenhouses. In this study, we compared the performance and transcriptomics of Solanum lycopersicum in response to B. terrestris and 2,4-D in greenhouse experiments. Tomato plants exposed to bumblebees had significantly higher fruiting rate and yield, weight and seed amounts, and significantly improved vitamin C, lycopene, soluble sugar contents, compared to hormone treatment. Bumblebee-treated tomatoes had 1171 significantly up-regulated genes, mainly enriched in photosynthesis, response to wounding, flavonoid biosynthesis, and carbohydrate biosynthetic process. By contrast, a total of 718 genes of 2,4-D-treated tomatoes were significantly up-regulated, which were mainly enriched in UDP-glucosyltransferase activity, response to chemical or auxin. Quantitative real-time PCR analysis of 14 candidate genes all exhibited good reproduction with the transcriptome data. These responses implied that bumblebee-treated tomatoes had improved photosynthesis and carbon-fixation capacity compared to 2,4-D-treated tomatoes. The use of bumblebees, as natural pollinators should be widely adopted in greenhouse horticulture to increase tomato yields and its nutritional contents.