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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Food Quality Laboratory » Research » Publications at this Location » Publication #322572
Title: Over-expression of polyphenol oxidase gene in strawberry fruit delays the fungus infection process

Author
item JIA, HAIFENG - Nanjing Agricultural University
item WANG, BAOJUN - Nanjing Agricultural University
item PERVAIZ, TARIQ - Nanjing Agricultural University
item ZHAO, FANGGUI - Jiangsu Academy Agricultural Sciences
item WANG, QINGLIAN - Jiangsu Academy Agricultural Sciences
item Yang, Tianbao
item FANG, JINGGUI - Nanjing Agricultural University

Submitted to: Plant Molecular Biology Reporter
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/12/2015
Publication Date: 6/1/2016
Citation: Jia, H., Wang, B., Pervaiz, T., Zhao, F., Wang, Q., Yang, T., Fang, J. 2016. Over-expression of polyphenol oxidase gene in strawberry fruit delays the fungus infection process. Plant Molecular Biology Reporter. 24:592-606.

Interpretive Summary: Polyphenols are secondary metabolites widely present in plants, and beneficial to human health. However, the regulation mechanics of polyphenol oxidation is not fully understood. This study analyzed the changes of polyphenol contents during strawberry fruit development as well as the changes of polyphenol oxidase (PPO), the enzyme that catalyzes the chemical reaction of phenolics. Both polyphenol content and PPO activity showed declining trend during fruit development, and mechanic damage to fruit enhanced the PPO activity. There are four PPO genes, and over-expression of one PPO improved the PPO activity in strawberry fruit, and delayed the fungus infection process. Furthermore, two PPO gene expression were regulated by both abiotic stresses, such as low temperature and salt, and biotic stresses of powdery mildew disease and gray mold. These results are useful to strawberry breeders for developing new varieties with improved disease resistance and fruit quality.

Technical Abstract: Polyphenols are secondary metabolites widely present in plants and beneficial to human health. In this study, the changes of polyphenol contents during strawberry fruit development as well as changes of polyphenol oxidase (PPO) was analyzed. The polyphenol content showed declining trend during fruit development. pH value in fruit impacted the PPO activity, and the optimal pH for the PPO activity was 4.5. PPO activity kept decreasing during fruit development, too. The fruit damage enhanced the PPO activity. Four PPO genes had different expression levels in tissues. Over-expression of the FaPPO1 genes improved the PPO activity in strawberry fruit, and delayed the fungus infection process. The FaPPO1 gene expression changes affected the pathogen related genes expression, such as PAL, SOD, POD, BG, and Chitinase genes. The fruit damage induced the FaPPO1 gene expression, and the abscisic acid and methyl jasmonate were also involved in the regulation of FaPPO1 gene expression. Further, the FaPPO1 and FaPPO2 gene expression were regulated both, by abiotic stresses of low temperature, NaCl and H2O2, and biotic stresses of powdery mildew and gray mold. These results will be helpful for understanding of the regulation mechanism of PPO to breed new varieties with increased fruit quality and enhanced disease resistance.