Transcriptome Analysis Provides Insights into the Mechanism of the Transcription Factor AaCrz1 Regulating the Infection Structure Formation of Alternaria alternata Induced by Pear Peel Wax Signal

Alternaria alternata, a causal agent of pear black spot, can recognize and respond to physicochemical signals from fruit surfaces through an intricate signaling network to initiate infection. Crz1 is an important transcription factor downstream of the calcium signaling pathway. In this study, we first investigated the infection structure formation process of the wild type (WT) and Delta AaCrz1 strains induced by the cuticular wax of the "Zaosu" pear by microscopic observation. We found that the infection process was delayed and the rate of appressorium formation and infection hyphae formation was significantly decreased in the Delta AaCrz1 strain. RNA-seq of WT and Delta AaCrz1 strains was analyzed after 6 h of induction with pear wax. A total of 893 up-regulated and 534 down-regulated genes were identified. Among them, genes related to cell wall degrading enzymes, ABC transporters, and ion homeostasis were down-regulated, and the autophagy pathway was induced and activated. In addition, disruption to the intracellular antioxidant system was also found after AaCrz1 knockdown. In summary, this study provides new information on the mechanism of the transcription factor AaCrz1 in the regulation of infection structure formation of A. alternata induced by pear peel wax signal, which can be used to develop new strategies for controlling fungal diseases in the future.