Elucidation of the Initial Growth Process and the Infection Mechanism of Penicillium digitatum on Postharvest Citrus (Citrus reticulata Blanco)

Abstract

Green mold disease, a common citrus post-harvest disease caused by Penicillium digitatum, has an unresolved initial infection mechanism. Understanding the infection mechanism leads to the development of potential controls and preventive measures against the disease. The present study aimed to delineate the infection mechanism by investigating spore germination, changes of organic molecules and enzyme activity, and differential expression of genes in the P. digitatum infection. P. digitatum spore germination was observed by a pathology section scanner and it was found that in vivo germination was 3 h behind the in vitro germination. In addition, cell wall degrading enzymes and soluble sugar and titratable acid content during the infection process measured dynamically. The level of pectinase reached its maximum of 6067 U/g before 48 hpi, while cellulase increased rapidly after 48 hpi. The soluble sugar and organic acid content increased considerably with the progression of the infection. The transcriptomic profile of P. digitatum before and after infection was analyzed by RNA-seq. The genes related to cell wall degrading enzymes were significantly up-regulated and annotated to participate in two major carbon source synthesis pathways. The study delineated the initial infection mechanism of P. digitatum which eventually opened the gate way for the development of new control strategies in the future.

Study on the Infection Mechanism of Penicillium Digitatum on Postharvest Citrus (Citrus Reticulata Blanco) Based on Transcriptomics

“…CWDEs are the most frequently reported pathogenic factors of plant pathogens. The large number of genes, associated with the synthesis of CWDEs, found in this study were already reported in our previous study [12]. In addition, the pH of the host environment is closely related to the synthesis and activity of CWDEs.…”

“…However, transcriptome analysis hasn't been used to determine the infection mechanism of P. digitatum in citrus fruits and thus the molecular mechanism behind the infection process is lacking. Therefore, this study sampled the P. digitatum infection in citrus at key time points as revealed in our previous study [12], and explored the key genes and pathways through high-throughput transcriptome sequencing, that reveal its infection mechanism at the molecular level. P. digitatum spores can activate rapidly and start colonization after they come into contact with citrus wounds.…”

“…The pathogen was isolated in our previous work and identified as P. digitatum [12]. The P. digitatum were cultured on potato dextrose agar (PDA) medium at 25 • C for 7 days, then spores were collected and the concentration was adjusted to 1 × 10 6 spores/mL suspension with normal saline.…”

“…Transcriptomics can comprehensively and intuitively display the gene expression of pathogenic fungi in the process of infection, and thus can similarly delineate the molecular mechanism of P. digitatum infection in postharvest citrus. In our previous work, through microscopic observation, enzyme activity, and physical and chemical determination, the key time point (44 h post-inoculation) of P. digitatum infection on citrus was determined [12]. In this study, we performed high-throughput transcriptome sequencing of P. digitatum in the early stages of infection (0-44 h post-inoculation).…”

UHPLC-Q-TOF/MS-Based Metabolomics Approach Reveals the Antifungal Potential of Pinocembroside against Citrus Green Mold Phytopathogen

“…Among these pathogens, P. digitatum, the causal agent of green mold, is considered one of the most threatening postharvest diseases in citrus fruit. The P. digitatum infection on citrus fruit has posed a series of adverse effects including toxins accumulation, postharvest deterioration, human health, environmental pollution, and 60-80% of postharvest crop loss in China [7,8]. To reduce the incidence of green mold, a variety of synthetic fungicides have been commonly used to ensure a stable supply of citrus fruit at markets for a growing world population [9,10].…”