Abstract
This study explored the mechanism of melon resistance to Alternaria alternata (A. alternata) infection in Jiashi and 86-1 melons. Melons were inoculated with A.alternata and the change in lesion diameter was measured. The changes in cinnamic acid-4-hydroxylase (C4H), phenylalanine ammonia lyase (PAL), and 4-coumaric acid coenzyme A ligase (4CL) activity and gene expression were studied in the pericarp tissues of Jiashi and 86-1 melons. The lesion diameter was smaller in Jiashi melon than in 86-1 melon, and the pericarp lesions were smaller than pulp lesions, indicating that Jiashi melon can resist A. alternata infection better than 86-1 melon. After inoculation with A. alternata, the C4H, PAL, and 4CL activities of Jiashi and 86-1 melons peaked in the middle and late storage period, and the peak was higher in Jiashi melons. The gene expression changes were consistent with the enzyme activity. The C4H, PAL, and 4CL gene expression was significantly higher in Jiashi melon pericarp than in 86-1 melon, and the C4H, PAL, and 4CL activities in Jiashi melon were positively correlated with their gene expression, confirming the role of phenylpropanoid metabolism enzymes in resistance to A. alternata.
Highlights
Xinjiang is the largest production area for high-quality muskmelon (Cucumis melo L.) in the world [1]
The pericarps of the two melons significantly (P < 0.05) inhibited the increase in A. alternata lesion diameter compared with the pulp
We found that after the melons were inoculated with A. alternata, the activity of phenylpropanoid metabolism enzymes increased in the pericarp tissue, which plays an important role in protecting melons from pathogenic bacteria
Summary
Xinjiang is the largest production area for high-quality muskmelon (Cucumis melo L.) in the world [1]. RNA extraction and first strand cDNA synthesis reaction Total RNA was isolated from pericarp tissue on Jiashi and 86-1 melons collected and frozen in liquid nitrogen immediately every 3 days, using the protocol from the TransZol Up (TransGen Biotech, ET111, Beijing, China). There was no significant difference in PAL activity between infected and control Jiashi melons in the early stage of storage, but the difference became significant when the activity peaked on day 21 (P < 0.01).
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