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Journal of Integrative Agriculture  2022, Vol. 21 Issue (12): 3578-3588    DOI: 10.1016/j.jia.2022.08.030
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Overexpression of the apple expansin-like gene MdEXLB1 accelerates the softening of fruit texture in tomato

CHEN Yan-hui1*, XIE Bin1*, AN Xiu-hong2, MA Ren-peng1, ZHAO De-ying1, CHENG Cun-gang1, LI En-mao1, ZHOU Jiang-tao1, KANG Guo-dong1, ZHANG Yan-zhen1

1 Key Laboratory of Mineral Nutrition and Efficient Fertilization for Deciduous Fruits, Liaoning Province/Key Laboratory of Fruit Germplasm Resources Utilization, Ministry of Agriculture and Rural Afffairs/Institute of Pomology, Chinese Academy of Agricultrual Sciences, Xingcheng 125100, P.R.China

2 National Engineering Research Center for Agriculture in Northern Mountainous Areas/Mountainous Area Research Institute, Hebei Agricultural University, Baoding 071001, P.R.China

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Fruit firmness is an important quality trait of apple fruit texture, and the pre-harvest ripening period is the key period for the formation of apple fruit texture.  Expansin is a cell wall loosing protein family that has four subfamilies: α-expansin (EXPA), β-expansin (EXPB), expansin-like A (EXLA), and expansin-like B (EXLB).  In this study, we investigated the key period of pre-harvest texture formation in ‘Golden Delicious’ apples based on fruit longitudinal diameter, transverse diameter, firmness, tissue structure, respiration intensity, ethylene release rate, and expansin activity.  Within the 10 days before harvest, the fruit was found to reach maturity.  Semi-quantitative RT-PCR revealed that most of the expansins were expressed at the ripening stage before harvest.  The biological function of the EXLB subfamily gene, MdEXLB1, was further identified, and its subcellular localization on the cell wall was confirmed by transient transformation experiments.  Compared with the wild type (WT), the transgenic tomato lines overexpressing MdEXLB1 had lower plant height, earlier fruiting period, fewer days for fruit ripening, higher fruit maturity, lower fruit firmness, higher fruit expansin activity, more discrete flesh cell structure, and accelerated fruit ripening process.  Overall, this is the first study to propose that the apple EXLB subfamily gene, MdEXLB1, has biological functions and plays an important role in promoting fruit ripening and softening.

Keywords:  fruit firmness       expansin        apple        transgenic tomato  
Received: 04 March 2022   Accepted: 25 May 2022
Fund: This work was supported by the National Key R&D Program of China (2016YFD0201100), the earmarked fund for China Agriculture Research System (CARS-27), the National Natural Science Foundation of China (31672116), and the Natural Science Foundation of Hebei Province, China (C2021204134).
About author:  CHEN Yan-hui, E-mail:; XIE Bin, E-mail:; Correspondence ZHAO De-ying, Tel: +86-429-3598203, E-mail:; CHENG Cun-gang, Tel/Fax: +86-429-3598158, E-mail: * These authors contributed equally to this study.

Cite this article: 

CHEN Yan-hui, XIE Bin, AN Xiu-hong, MA Ren-peng, ZHAO De-ying, CHENG Cun-gang, LI En-mao, ZHOU Jiang-tao, KANG Guo-dong, ZHANG Yan-zhen. 2022. Overexpression of the apple expansin-like gene MdEXLB1 accelerates the softening of fruit texture in tomato. Journal of Integrative Agriculture, 21(12): 3578-3588.

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