Physiological and transcriptomic analysis of tomato in response to sub-optimal temperature stress

Tomato (Solanum lycopersicum L.) is one of the most important economic crops in China. However, its quality and yield are susceptible to the adverse effects of low temperatures. In our study, two tomato cultivars, showing different tolerance to low temperatures, namely the cold-sensitive tomato cultivar (S708) and cold-tolerant tomato cultivar (T722), were grown at optimal (25/18°C) and sub-optimal (15/10°C) temperature conditions for 5 days. Our study aimed to explore the effect of sub-optimal temperature on fresh weight, chlorophyll content and chlorophyll fluorescence, soluble sugars and proline content of two tomato cultivars. Moreover, we employed RNA-Seq to analyze the transcriptomic response of tomato roots to sub-optimal temperature. The results revealed that S708 showed a more significant reduction in fresh weight, chlorophyll content, photochemical efficiency of PSII (YII), maximum quantum yield of PSII (Fv/Fm), photochemical quenching (qP) and electron transport rate (ETR) compared to T722 under the sub-optimal temperature condition. Notably, T722 maintained higher level of soluble sugars and proline in comparison to S708 uner sub-optimal temperature. RNA-seq data showed that up-regulated DEGs in both tomato cultivars were involved in “plant-pathogen interaction”, “MAPK signaling pathway”, “plant hormone signal transduction”, and “phosphatidylinositol signaling system”. Furthermore, “Amino sugar and nucleotide sugar metabolism” pathway was enriched only in T722. Moreover, under sub-optimal temperature, transcription factor genes and osmoregulation genes showed varying degrees of response in both tomato cultivars. Conclusion: In summary, our results offer detailed insights into the response characteristics of tomato to sub-optimal temperature, providing valuable references for the practical management of tomato crops under sub-optimal temperature condition.

番茄（Solanum lycopersicum L.）是中国最重要的经济作物之一。然而其品质与产量极易受到低温的不利影响。本研究选取对低温耐受性存在差异的两个番茄品种：低温敏感型番茄品种S708与耐低温型番茄品种T722，分别置于适宜温度（25/18℃）与亚适宜温度（15/10℃）环境下培养5天。本研究旨在探究亚适宜温度对两个番茄品种的鲜重、叶绿素含量、叶绿素荧光参数、可溶性糖及脯氨酸含量的影响。此外，本研究采用RNA测序（RNA-Seq）技术分析番茄根系对亚适宜温度的转录组响应。研究结果显示，在亚适宜温度条件下，相较于T722，S708的鲜重、叶绿素含量、光系统II（PSII）光化学效率（YII）、PSII最大量子产额（Fv/Fm）、光化学淬灭系数（qP）以及电子传递速率（ETR）均出现更为显著的下降。值得注意的是，在亚适宜温度环境中，T722的可溶性糖与脯氨酸含量均高于S708。RNA测序数据显示，两个番茄品种中上调的差异表达基因（DEGs）均富集于"植物-病原体互作"、"丝裂原活化蛋白激酶（MAPK）信号通路"、"植物激素信号转导"以及"磷脂酰肌醇信号系统"通路。此外，"氨基糖与核苷酸糖代谢"通路仅在T722中得到富集。此外，在亚适宜温度条件下，两个番茄品种的转录因子基因与渗透调节基因均呈现出不同程度的响应。结论：综上，本研究结果详细阐明了番茄对亚适宜温度的响应特征，可为亚适宜温度环境下番茄作物的田间管理提供重要参考依据。