Transcriptome analysis of aroma volatile metabolism change in tomato (Solanum lycopersicum) fruit under different storage temperatures and 1-MCP treatment

Temperature control and ethylene inhibitor 1-methylcyclopropene (1-MCP) treatment are the main techniques for increasing the shelf life of tomato (Solanum lycopersicum L.) fruit. However, these techniques could strongly affect the aromatic flavor of tomato. In this study, RNA-sequencing was employed to characterize the transcriptomic profiles of cherry tomato fruit, harvested at breaker stage, during postharvest storage under different temperatures (25 degrees C, 10 degrees C, and 4 degrees C) and at 10 degrees C after 1-MCP treatment. Results showed that storage temperature remarkably affected the expression of numerous genes in tomato fruit, especially on several key genes associated with aroma volatile biosynthesis. It was found that 33 genes presented significantly different expression between 10 degrees C and 25 degrees C, and in particular, five genes expressed significantly lower at 10 degrees C than that at 25 degrees C, including CCD1, GOT1, ADH2, PDC1-likel, and PDC1-like2, mainly involved in the syntheses of pseudoionone, beta-ionone, phenylacetaldehyde, phenylethylalcohol, cis-3-hexenol, and trans-3-Hexenol. The expression level of other 14 genes associated with aroma volatile biosynthesis was lower at 4 degrees C than that at 10 degrees C, among which, five genes, including TPS24, PDS, ACOT9-like, ADH2 and AAT were directly related to the biosynthesis of terpenoids, alcohols and esters. Only few genes associated with aroma volatiles were affected by 1 MCP treatment at 10 degrees C. The presented results implied that the recommended storage temperature of 10 degrees C is able to result in a significant negative effect on the aromatic flavor of tomato at the gene transcriptional level, which could explain the flavor loss of tomato under market storage temperatures (8-12 degrees C) and household refrigerator temperatures (3-5 degrees C). To be mentioned, our results provide strong evidence that 10 degrees C, as the recommended storage temperature for tomato fruit, is not ideal to maintain the flavor quality of tomato, and 1 MCP treatment under 10 degrees C cannot further affect the flavor quality of tomato fruit compared with that at 10 degrees C alone.