Liang Zhaolin, Liu Kai, Jiang Chunyang, Yang An, Yan Jiadi, Han Xiaolei, Zhang Caixia, Cong Peihua, Zhang Liyi
Research Institute of Pomology, Chinese Academy of Agricultural Sciences, Xingcheng, China.
Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (Germplasm Resources Utilization), Research Institute of Pomology, Chinese Academy of Agricultural Sciences, Ministry of Agriculture, Xingcheng, China.
Front Plant Sci. 2022 Dec 29;13:1090621. doi: 10.3389/fpls.2022.1090621. eCollection 2022.
Alternaria blotch disease, caused by apple pathotype (AAAP), is one of the major fungal diseases in apple. Early field observations revealed, the anther-derived homozygote Hanfu line (HFTH1) was highly susceptible to AAAP, whereas Hanfu (HF) exhibited resistance to AAAP. To understand the molecular mechanisms underlying the difference in sensitivity of HF and HFTH1 to AAAP, we performed allele-specific expression (ASE) analysis and comparative transcriptomic analysis before and after AAAP inoculation. We reported an important immune gene, namely, , which displayed strong ASE in HF with much lower expression levels of HFTH1-derived alleles. Transient overexpression of the dominant allele of from HF in GL-3 apple leaves could enhance resistance to AAAP and induce expression of genes related to salicylic acid pathway. In addition, was identified with an insertion of an 85-bp terminal-repeat retrotransposon in miniature (TRIM) element-like sequence in the upstream region of the nonreference allele. In contrast, only one terminal direct repeat (TDR) from TRIM-like sequence was present in the upstream region of the HFTH1-derived allele Furthermore, the results of luciferase and β-glucuronidase reporter assays demonstrated that the intact TRIM-like sequence has enhancer activity. This suggested that insertion of the TRIM-like sequence regulates the expression level of the allele of , in turn, affecting the sensitivity of HF and HFTH1 to AAAP.
交链孢斑点病由苹果致病型（AAAP）引起，是苹果主要的真菌病害之一。早期田间观察发现，花药来源的纯合子寒富株系（HFTH1）对AAAP高度敏感，而寒富（HF）对AAAP表现出抗性。为了解HF和HFTH1对AAAP敏感性差异的分子机制，我们在接种AAAP前后进行了等位基因特异性表达（ASE）分析和比较转录组分析。我们报道了一个重要的免疫基因，即 ，其在HF中表现出强烈的ASE，而HFTH1来源的等位基因表达水平低得多。在GL-3苹果叶片中瞬时过表达HF的 显性等位基因可增强对AAAP的抗性并诱导水杨酸途径相关基因的表达。此外，在非参考等位基因上游区域鉴定出 插入了一个85bp的微型末端重复反转录转座子（TRIM）样序列。相比之下，HFTH1来源的等位基因 上游区域仅存在一个来自TRIM样序列的末端直接重复序列（TDR）。此外，荧光素酶和β-葡萄糖醛酸酶报告基因检测结果表明完整的TRIM样序列具有增强子活性。这表明TRIM样序列的插入调节了 等位基因的表达水平，进而影响HF和HFTH1对AAAP的敏感性。
