Comparative transcriptomics provides insights into the pathogenic immune response of brown leaf spots in weeping forsythia.

Weeping forsythia is an important ornamental, ecological and medicinal plant. Brown leaf spots limit the large-scale production of weeping forsythia as a medicinal crop. Alternaria alternata is a pathogen causing brown leaf spots in weeping forsythia; however, its pathogenesis and the immune response mechanisms of weeping forsythia remain unclear. In this study, we identified two mechanisms based on morphological anatomy, physiological indexes and gene expression analyses. Our results showed that A. alternata induced leaf stomata to open, invaded the mesophyll, dissolved the cell wall, destroyed the cell membrane and decreased the number of chloroplasts by up-regulating the expression of auxin-activated signaling pathway genes. Alternaria alternata also down-regulated iron-ion homeostasis and binding-related genes, which caused an increase in the levels of iron ions and reactive oxygen species in leaves. These processes eventually led to programmed cell death, destroying palisade and spongy tissues and causing the formation of iron rust spots. Alternaria alternata also caused defense and hypersensitive responses in weeping forsythia through signaling pathways mediated by flg22-like and elf18-like polypeptides, ethylene, H2O2 and bacterial secretion systems. Our study provides a theoretical basis for the control of brown leaf spots in weeping forsythia. © The Author(s) 2023. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Citation

Wang-Jun Yuan, Zhi-Yin He, Su-Ping Zhang, Yan-Ping Zheng, Xiao-Qian Zhang, She-Qi He, Yan-Xia He, Yong Li. Comparative transcriptomics provides insights into the pathogenic immune response of brown leaf spots in weeping forsythia. Tree physiology. 2023 Sep 06;43(9):1641-1652

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PMID: 37171622

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