• Food Science and Biotechnology
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• v.16 no.2
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• pp.294-298
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• 2007

The actinidin (EC 3.4.22. 14) found in kiwifruit is a cysteine protease. In order to obtain the actinidin gene from the Chinese wild kiwifruit, primers were designed on the basis of the actinidin gene of Actinidia deliciosa, the New Zealand kiwifruit. The 1.2 kb DNA fragment was acquired from the total RNAs of Chinese wild kiwifruit via reverse transcription polymerase chain reaction (RT-PCR), and its DNA sequence was analyzed. Its sequence was determined to share 98.4% homology with the actinidin gene of A. deliciosa. In order to verity the actinidin gene isolated from the Chinese wild kiwifruit in Escherichia coli, the mature gene was amplified via PCR and expressed in E. coli under the control of the T7lac promoter. The actinidin was expressed in E. coli as inclusion bodies, which were solubilized with urea and refolded. The protease activity of the refolded protein was approximately twice as high as that of E. coli BL2l (DE3).

• The Plant Pathology Journal
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• v.35 no.4
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• pp.372-380
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• 2019

Pseudomonas syringae pv. actinidiae (Psa) is by far the most important pathogen of kiwifruit. Sustainable expansion of the kiwifruit industry requires the use of Psa-tolerant or resistant genotypes for the breeding of tolerant cultivars. However, the resistance of most existing kiwifruit cultivars and wild genotypes is poorly understood, and suitable evaluation methods of Psa resistance in Actinidia have not been established. A unique in vitro method to evaluate Psa resistance has been developed with 18 selected Actinidia genotypes. The assay involved debarking and measuring the lesions of cane pieces inoculated with the bacterium in combination with the observation of symptoms such as callus formation, sprouting of buds, and the extent to which Psa invaded xylem. Relative Psa resistance or tolerance was divided into four categories. The division results were consistent with field observations. This is the first report of an in vitro assay capable of large-scale screening of Psa-resistance in Actinidia germplasm with high accuracy and reproducibility. The assay would considerably facilitate the breeding of Psa-resistant cultivars and provide a valuable reference and inspiration for the resistance evaluation of other plants to different pathogens.