Lignin Biosynthesis Pathway and Redox Balance Act Synergistically in Conferring Resistance against Penicillium italicum Infection in 7-Demethoxytylophorine-Treated Navel Orange

Abstract

7-Demethoxytylophorine (DEM), a natural water-soluble phenanthroindolizidine alkaloid, has a great potential for in vitro suppression of Penicillium italicum growth. In the present study, we investigated the ability of DEM to confer resistance against P. italicum in harvested “Newhall” navel orange and the underlying mechanism. Results from the in vivo experiment showed that DEM treatment delayed blue mold development. The water-soaked lesion diameter in 40 mg L–1 DEM-treated fruit was 35.2% lower than that in the control after 96 h. Moreover, the decrease in peel firmness loss and increase in electrolyte leakage, superoxide anion (O2 •–) production, and malondialdehyde (MDA) content were significantly inhibited by DEM treatment. Hydrogen peroxide (H2O2) burst in DEM-treated fruit at the early stage of P. italicum infection contributed to the conferred resistance by increasing the activities of lignin biosynthesis-related enzymes, along with the expressions of their encoding genes, resulting in lignin accumulation. The DEM-treated fruit maintained an elevated antioxidant capacity, as evidenced by high levels of ascorbic acid and glutathione content, and enhanced or upregulated the activities and gene expression levels of APX, GR, MDHAR, DHAR, GPX, and GST, thereby maintaining ROS homeostasis and reducing postharvest blue mold. Collectively, the results in the present study revealed a control mechanism in which DEM treatment conferred the resistance against P. italicum infection in harvested “Newhall” navel orange fruit by activating lignin biosynthesis and maintaining the redox balance.

Levulinic acid as a strategy for control of postharvest citrus blue mold by a newly isolated Penicillium italicum

“…The production of antioxidant enzymes is a mechanism for eliminating ROS that plants and plant tissues develop when attacked to minimize oxidative stress and eliminate these species, reducing fruit electrolyte leakage, lipid damage to the cell membrane, and organelle damage. CAT and APX are efficient eliminators of ROS, whereas POD is linked to fruit resistance, which increases as a consequence of fungal proliferation in the host 6,30‐33 . The increase in these enzymes is, therefore, associated with the manifestation of the resistance system of the plant tissue when attacked by the fungus.…”

“…CAT and APX are efficient eliminators of ROS, whereas POD is linked to fruit resistance, which increases as a consequence of fungal proliferation in the host. 6,[30][31][32][33] The increase in these enzymes is, therefore, associated with the manifestation of the resistance system of the plant tissue when attacked by the fungus. Our study showed no increased production of antioxidant enzymes in the LA treatments.…”

“…Generally, studies evaluate compounds, products and even microorganisms that can induce and increase the fruit's resistance to pathogens, or even delay the onset of blue mold, leading to increased enzymatic activities. 30,[32][33][34] . In the present research, as the pathogen was inhibited before infecting the fruit, even when inoculated under conditions favorable for disease proliferation, the rates of enzymatic activities in the target treatment were lower.…”

Fumonisin B1 Biosynthesis Is Associated with Oxidative Stress and Plays an Important Role in Fusarium proliferatum Infection on Banana Fruit

“…In response to pathogen attack, plants establish a broad range of defense responses to protect themselves, including rapid production of reactive oxygen species (ROS). , Importantly, disease development in harvested fruit also results from the disorder of ROS metabolism. , Hence, ROS stress is one of the most important stresses confronted by fungi during the infection process. In turn, ROS detoxification is critical for the pathogenicity of pathogens .…”

“…8,9 Importantly, disease development in harvested fruit also results from the disorder of ROS metabolism. 10,11 Hence, ROS stress is one of the most important stresses confronted by fungi during the infection process. In turn, ROS detoxification is critical for the pathogenicity of pathogens.…”