Data Sheet 1_Multifactor transcriptional profiling of potato during 2,4-D-induced resistance to common scab disease.pdf

Foliar application of low-dose 2,4-dichlorophenoxyacetic acid (2,4-D) has been demonstrated to reduce potato common scab disease caused by phytopathogenic Streptomyces. Foliar-applied 2,4-D is translocated to the tubers but does not cause direct toxicity against the pathogen. The efficacy of 2,4-D treatment for common scab disease management is inconsistent among field trials in the literature, and the exact mode of action is unknown. Here, we identified transcriptomic responses of potato to low-dose 2,4-D treatment in the presence and absence of the pathogen and in tuber periderm and foliar tissue. Pathogen infection primarily altered transcriptomic responses in tuber periderm tissue, while foliar 2,4-D application caused larger shifts in gene expression in leaf tissue, as expected. Gene ontology (GO) terms associated with pathogen defense, stress responses, and enzymatic inhibitors were significantly enriched among differentially expressed genes in the tuber response to the pathogen. There were more differentially expressed genes and enriched GO terms in response to the pathogen when plants were treated with 2,4-D than in the non-2,4-D-treated plants, including differentially expressed genes and GO terms related to lipases, jasmonic acid signaling, and transport. Fewer differentially expressed genes were identified in tuber tissue than in leaf tissue following foliar 2,4-D treatment, but GO terms related to sucrose transport were enriched in tuber RNA samples from 2,4-D-treated, non-inoculated plants. Altered glucose and fructose, but not sucrose, levels in tuber medulla and periderm tissue, the site of common scab infection, were observed in 2,4-D-treated plants. Utilizing multiple factors, i.e., mock or 2,4-D treatments in both the presence and absence of the pathogen, in parallel transcriptional profiling experiments enabled the identification of pathways that directly respond to 2,4-D treatment in both foliar and tuber tissue and pathways with altered response in the context of pathogen infection. Identifying tools to more consistently induce these changes may enable more robust disease management than indirect foliar 2,4-D treatments.

低剂量2,4-二氯苯氧乙酸（2,4-dichlorophenoxyacetic acid，2,4-D）叶面喷施已被证实可减轻由致病性链霉菌（Streptomyces）引发的马铃薯普通疮痂病。叶面施用的2,4-D可转运至块茎，但不会对该病原菌产生直接毒性作用。现有文献报道的田间试验表明，2,4-D用于马铃薯普通疮痂病防治的效果并不稳定，且其确切作用机制至今不明。本研究解析了在病原菌存在与缺失两种条件下，以及块茎周皮与叶片组织中，马铃薯对低剂量2,4-D处理的转录组响应。正如预期，病原菌侵染主要改变块茎周皮组织的转录组特征，而叶面喷施2,4-D则使叶片组织的基因表达发生更为显著的变化。在马铃薯块茎对病原菌的响应过程中，与病原菌防御、胁迫响应及酶抑制剂相关的基因本体论（Gene Ontology，GO）条目在差异表达基因中显著富集。相较于未施用2,4-D的植株，经2,4-D处理的植株在应对病原菌侵染时，其差异表达基因及富集GO条目更多，涵盖与脂肪酶、茉莉酸信号传导及物质转运相关的基因与GO条目。叶面喷施2,4-D后，块茎组织中鉴定出的差异表达基因数量少于叶片组织，但在未接种病原菌且经2,4-D处理的植株的块茎RNA样本中，与蔗糖转运相关的GO条目得到显著富集。经2,4-D处理的植株在普通疮痂病的侵染位点——块茎髓部与周皮组织中，检测到葡萄糖和果糖（而非蔗糖）的含量发生改变。本研究通过设置Mock处理（空白对照）与2,4-D处理，且分别在病原菌存在与不存在的条件下开展平行转录组分析实验，成功鉴定出两类通路：一类是在叶片与块茎组织中均直接响应2,4-D处理的通路，另一类是在病原菌侵染背景下响应发生改变的通路。开发能更稳定诱导上述变化的工具，或可实现比间接叶面喷施2,4-D更为可靠的病害防治效果。