State Key Laboratory of Resource Insects, Institute of Sericulture and Systems Biology, Southwest University, Chongqing, China.
Resource Institute for Chinese & Ethnic Materia Medica, Guizhou University of Traditional Chinese Medicine, Guiyang, China.
Mol Plant Pathol. 2024 Nov;25(11):e70023. doi: 10.1111/mpp.70023.
Ciboria shiraiana is a necrotrophic fungus that causes mulberry sclerotinia disease resulting in huge economic losses in agriculture. During infection, the fungus uses immunity elicitors to induce plant tissue necrosis that could facilitate its colonization on plants. However, the key elicitors and immune mechanisms remain unclear in C. shiraiana. Herein, a novel elicitor Cs08297 secreted by C. shiraiana was identified, and it was found to target the apoplast in plants to induce cell death. Cs08297 is a cysteine-rich protein unique to C. shiraiana, and cysteine residues in Cs08297 were crucial for its ability to induce cell death. Cs08297 induced a series of defence responses in Nicotiana benthamiana, including the burst of reactive oxygen species (ROS), callose deposition, and activation of defence-related genes. Cs08297 induced-cell death was mediated by leucine-rich repeat (LRR) receptor-like kinases BAK1 and SOBIR1. Purified His-tagged Cs08297-thioredoxin fusion protein triggered cell death in different plants and enhanced plant resistance to diseases. Cs08297 was necessary for sclerotial development, oxidative-stress adaptation, and cell wall integrity but negatively regulated virulence of C. shiraiana. In conclusion, our results revealed that Cs08297 is a novel fungal elicitor in fungi inducing plant immunity. Furthermore, its potential to enhance plant resistance provides a new target to control agricultural diseases biologically.
白僵菌是一种坏死型真菌，可引起桑疫病，给农业造成巨大经济损失。在侵染过程中，真菌利用免疫激发子诱导植物组织坏死，从而促进其在植物上的定殖。然而，白僵菌中的关键激发子和免疫机制仍不清楚。在此，鉴定了一种白僵菌分泌的新型激发子 Cs08297，它靶向植物的质外体诱导细胞死亡。Cs08297 是白僵菌特有的富含半胱氨酸的蛋白质，半胱氨酸残基对其诱导细胞死亡的能力至关重要。Cs08297 在本氏烟中诱导了一系列防御反应，包括活性氧（ROS）爆发、胼胝质沉积和防御相关基因的激活。Cs08297 诱导的细胞死亡是由富含亮氨酸重复（LRR）受体样激酶 BAK1 和 SOBIR1 介导的。纯化的 His 标记的 Cs08297-硫氧还蛋白融合蛋白在不同植物中触发细胞死亡，并增强植物对疾病的抗性。Cs08297 对白僵菌的菌核发育、氧化应激适应和细胞壁完整性是必要的，但负调控其毒性。总之，我们的研究结果表明，Cs08297 是一种新型真菌激发子，可诱导植物免疫。此外，其增强植物抗性的潜力为生物防治农业病害提供了新的靶标。
