Objective To reveal the changes of morphological characteristics and amino acid metabolism in fruit of Sinopodophyllum hexandrum at different ripening stages. Methods The morphological characteristics, amino acid content, and related genes expression were determined and analyzed in fruit of S. hexandrum at different ripening stages（S1 to S9）. Results There were significant differences in morphological characteristics（e.g., fruit color, length, and diameter）, amino acid content, and related genes expression during fruit ripening. The fruit length, diameter, fresh weight, and dry weight showed a 2.2, 2.18, 31.42, and 49.05 fold increase at the S6 compared with S1; the content of amino acid were greater at the S5 and S9 than other stages; the 10 candidate genes related to amino acid metabolism [e.g., arginine decarboxylase 2（ADC2）, arogenate dehydratase 6（ADT6）, and asparagine synthetase（AS）] showed a down-regulation to some extent at S4 to S8 compared with S2. Conclusion There were dynamic differences in morphological characteristics, amino acid metabolism and related gene expression levels with fruit ripening. These finding will provide useful references for the development and utilization of S. hexandrum fruits.

Sinopodophyllum hexandrum Royle  /  fruit  /  ripening stage  /  morphological characteristic  /  amino acid metabolism  /  gene expression