College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, China.
Xuzhou Institute of Agricultural Sciences of Xuhuai Region of Jiangsu, Xuzhou, 221131, Jiangsu, China.
J Plant Physiol. 2022 Jun;273:153697. doi: 10.1016/j.jplph.2022.153697. Epub 2022 Apr 22.
Alternaria blotch disease, caused by Alternaria alternata apple pathotype (AAAP), is one of the most prevalent diseases in apple production. To identify AAAP resistance-related genes and provide a theoretical basis for Alternaria blotch disease resistance breeding, we used two apple cultivars, 'Jonathan', a variety resistant to AAAP infection, and 'Starking Delicious', a variety susceptible to AAAP infection, as materials to perform transcriptome sequencing of apple leaves 72 h after AAAP infection. A Venn diagram showed that a total of 5229 DEGs of 'Jonathan' and 4326 DEGs of 'Starking Delicious' were identified. GO analysis showed that these DEGs were clustered into 25 GO terms, primarily "metabolic process" and "catalytic activity." Functional classification analyses of the DEGs indicated that "MAPK signaling pathway-plant pathway" is the most significant metabolic pathway among the top 15 KEGG pathways, followed by the "plant hormone signal transduction" pathway. There are more DEGs in 'Jonathan' that are significantly classified GO terms and KEGG pathways than in 'Starking Delicious'. Specifically, 13 DEGs were identified as involved in the GA-GID1-DELLA module, and the expression of MdGRAS53, a homologous gene of DELLA, was significantly upregulated in 'Jonathan' compared with 'Starking Delicious'. Phenotype analysis revealed that exogenous hormone GA3 suppressed apple resistance to AAAP infection and reduced the expression of MdGRAS53. The opposite result was observed for exogenous spraying of paclobutrazol (PAC), an inhibitor of gibberellin synthesis. Overexpression of MdGRAS53 in apple leaves by transient transformation decreased lesion area and the number of spores in leaves infected with AAAP, while silencing MdGRAS53 showed the opposite result. Meanwhile, SA/JA signaling pathway-related genes were upregulated significantly in MdGRAS53-overexpressed leaves and downregulated significantly in MdGRAS53-silenced leaves. The findings suggest that the GA-GID1-DELLA module is involved in apple resistance to AAAP, and MdGRAS53, a DELLA homologous gene, may play a positive role in this resistance by modulating cooperative JA- and SA-dependent pathways.
链格孢斑点病，由链格孢苹果专化型（AAAP）引起，是苹果生产中最普遍的病害之一。为了鉴定 AAAP 抗性相关基因，并为链格孢斑点病抗性育种提供理论基础，我们以对 AAAP 感染具有抗性的品种‘Jonathan’和对 AAAP 感染敏感的品种‘Starking Delicious’为材料，对苹果叶片在 AAAP 感染后 72 h 进行转录组测序。Venn 图显示，‘Jonathan’共有 5229 个 DEGs，‘Starking Delicious’共有 4326 个 DEGs。GO 分析表明，这些 DEGs 被聚类到 25 个 GO 术语中，主要是“代谢过程”和“催化活性”。DEGs 的功能分类分析表明，在 15 个 KEGG 通路中，“MAPK 信号通路-植物途径”是最重要的代谢途径，其次是“植物激素信号转导”途径。在‘Jonathan’中，显著分类的 GO 术语和 KEGG 通路的 DEGs 比在‘Starking Delicious’中更多。具体来说，鉴定出 13 个 DEGs 参与 GA-GID1-DELLA 模块，与‘Starking Delicious’相比，‘Jonathan’中 DELLA 同源基因 MdGRAS53 的表达显著上调。表型分析表明，外源激素 GA3 抑制了苹果对 AAAP 感染的抗性，降低了 MdGRAS53 的表达。而赤霉素合成抑制剂多效唑（PAC）的外源喷雾则得到了相反的结果。通过瞬时转化在苹果叶片中过表达 MdGRAS53 可减少 AAAP 感染叶片的病斑面积和孢子数量，而沉默 MdGRAS53 则得到相反的结果。同时，MdGRAS53 过表达叶片中 SA/JA 信号通路相关基因显著上调，而 MdGRAS53 沉默叶片中显著下调。研究结果表明，GA-GID1-DELLA 模块参与了苹果对 AAAP 的抗性，DELLA 同源基因 MdGRAS53 可能通过调节协同的 JA 和 SA 依赖途径在这种抗性中发挥积极作用。
