Li Yi, Lou Huijie, Fu Hongyan, Su Hanying, Hao Chenxing, Luo Jianming, Cai Nan, Jin Yan, Han Jian, Deng Ziniu, Cao Yunlin, Ma Xianfeng
Engineering Research Center of Education Ministry for Germplasm Innovation and Breeding New Varieties of Horticultural Crops, College of Horticulture, Hunan Agricultural University, Changsha, 410128 China.
National Center for Citrus Improvement-Changsha, College of Horticulture, Hunan Agricultural University, Changsha, 410128 China.
Mol Breed. 2025 Jan 6;45(1):10. doi: 10.1007/s11032-024-01531-3. eCollection 2025 Jan.
Citrus canker is a devastating disease caused by subsp. (), which secretes the effector PthA4 into host plants to trigger transcription of the susceptibility gene , resulting in pustule formation. However, the molecular mechanism underlying CsLOB1-mediated susceptibility to remains elusive. This study identified as a target gene positively regulated by CsLOB1. Cell expansion and cell wall degradation were observed in sweet orange leaves after infection. A total of 69 cellulase genes were retrieved within the genome, comprising 40 endoglucanase genes and 29 glucosidase genes. Transcriptomic analysis revealed that expression levels of , , and were induced by invasion in sweet orange leaves, but not in the resistant genotype Citron C-05. Among them, exhibited the highest expression level, with an over 430-fold increase following infection. Additionally, RT-qPCR analysis confirmed that expression was induced in susceptible genotypes (Sweet orange, Danna citron, Lemon) upon invasion, but not in resistant genotypes (Citron C-05, Aiguo citron, American citron). A Single-Nucleotide Polymorphism (SNP) at -423 bp was identified in the promoters and exhibits a difference between eight susceptible citrus genotypes and three resistant ones. Moreover, expression was upregulated in -overexpression transgenic lines compared to the wild type. Dual-luciferase reporter assays indicated that CsLOB1 can target the -505 bp to -168 bp region of promoter to trans-activate its expression. These findings suggest that may function as a candidate gene for citrus canker development and may be a promising target for biotechnological breeding of -resistant citrus genotypes.
The online version contains supplementary material available at 10.1007/s11032-024-01531-3.
柑橘溃疡病是由 亚种（）引起的一种毁灭性病害，该病菌向寄主植物分泌效应蛋白PthA4，以触发感病基因 的转录，从而导致脓疱形成。然而，CsLOB1介导的对柑橘溃疡病菌的感病分子机制仍不清楚。本研究鉴定出 是受CsLOB1正向调控的靶基因。柑橘溃疡病菌侵染后，在甜橙叶片中观察到细胞扩张和细胞壁降解。在柑橘溃疡病菌基因组中总共检索到69个纤维素酶基因，包括40个内切葡聚糖酶基因和29个葡糖苷酶基因。转录组分析表明，、、 和 的表达水平在甜橙叶片受到柑橘溃疡病菌侵染时被诱导，但在抗性基因型枸橼C-05中未被诱导。其中， 表现出最高的表达水平，在柑橘溃疡病菌侵染后增加了430多倍。此外，RT-qPCR分析证实，柑橘溃疡病菌侵染后，感病基因型（甜橙、丹娜枸橼、柠檬）中 表达被诱导，但在抗性基因型（枸橼C-05、爱国枸橼、美国枸橼）中未被诱导。在 启动子的-423 bp处鉴定出一个单核苷酸多态性（SNP），其在8个感病柑橘基因型和3个抗病基因型之间存在差异。此外，与野生型相比， 在过表达转基因系中表达上调。双荧光素酶报告基因检测表明，CsLOB1可以靶向 启动子的-505 bp至-168 bp区域来反式激活其表达。这些发现表明， 可能作为柑橘溃疡病发生发展的候选基因，并且可能是抗柑橘溃疡病菌柑橘基因型生物技术育种的一个有前景的靶点。
在线版本包含可在10.1007/s11032-024-01531-3获取的补充材料。
