State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
Department of Plant Pathology, College of Plant Protection, China Agricultural University, Beijing 100193, China.
Int J Mol Sci. 2022 Aug 15;23(16):9144. doi: 10.3390/ijms23169144.
Bacterial fruit blotch (BFB) caused by (Ac) is a devastating watermelon disease that severely impacts the global watermelon industry. Like other Gram-negative bacteria, the type three secretion system (T3SS) is the main pathogenicity factor of . The T3SS apparatus gene codes for the Hrp pilus and serves as a conduit to secret effector proteins into host cells. In this study, we found that the deletion of in results in the loss of pathogenicity on hosts and the hypersensitive response on non-hosts. In addition, the mutant showed a reduction in in vitro growth, colonization, swimming and twitching motility, and displayed increases in biofilm formation ability compared to the wild type. However, when HrpE was transiently expressed in hosts, the defense responses, including reactive oxygen species bursts, callose deposition, and expression of defense-related genes, were activated. Thus, the growth in HrpE-pretreated hosts was suppressed. These results indicated that HrpE is essential for virulence but can also be used by hosts to help resist . Our findings provide a better understanding of the T3SS pathogenesis in , thus providing a molecular basis for biopesticide development, and facilitating the effective control of BFB.
细菌性果斑病（BFB）由 （Ac）引起，是一种严重影响全球西瓜产业的毁灭性西瓜病害。与其他革兰氏阴性菌一样，III 型分泌系统（T3SS）是 的主要致病性因子。T3SS 装置基因 编码 Hrp 菌毛，是将效应蛋白分泌到宿主细胞的通道。在本研究中，我们发现 中 的缺失导致在宿主上丧失致病性和在非宿主上发生过敏反应。此外，与野生型相比， 突变体在体外生长、定殖、泳动和翻滚运动方面的能力降低，生物膜形成能力增强。然而，当 HrpE 在宿主中瞬时表达时，会激活包括活性氧爆发、胼胝质沉积和防御相关基因表达在内的防御反应。因此，HrpE 预处理宿主中的 生长受到抑制。这些结果表明 HrpE 是 的毒力所必需的，但也可以被宿主用来帮助抵抗 。我们的研究结果提供了对 T3SS 发病机制的更好理解，从而为生物农药的开发提供了分子基础，并有助于有效控制 BFB。
