RNA-seq reveals molecular mechanisms behind chilling injury tolerance in ISW-treated zucchini fruit during cold storage

A. Chana-Muñoz, A. García, E. Aguado, J. Romero, G. Cebrián, J. Iglesias-Moya, D. Garrido, J. Cañizares, J.L. Valenzuela, M. Jamilena
Cucurbita pepo is an economically important horticultural crop of subtropical origin. In Spain, most of its production is destined for overseas markets, and freshly harvested (FH) fruits are stored and transported at low temperature in order to maintain their quality. Unfortunately, zucchini fruits are very sensitive to cold storage temperatures, showing different chilling injury (CI) symptoms such as pitting on the fruit surface and increased weight loss. Previous studies have shown individual shrink wrapping (ISW) as an efficient method to delay and attenuate CI symptoms in sensitive cultivars. ISW treatment induced biochemical and physiological changes that pointed toward a reduced ethylene signaling and ROS content as important processes behind this tolerance. However, a complete and detailed molecular analysis of additional pathways behind these processes is still limited. To overcome those limitations, RNA-seq (transcriptome sequencing) was performed on the exocarp of a CI-sensitive zucchini cultivar. Around 30 million reads were generated for FH, ISW and untreated fruits stored at 4°C for 14 days. Using HISAT2, about 96% of the reads were properly mapped to C. pepo 4.1 genome. Transcript reconstruction was performed with StringTie, and Deseq2 found a total of 6,728 and 4,366 differentially expressed genes (DEG) after comparing FH fruit with ISW-treated and non-treated fruit, respectively. Among them, 2,895 genes were selected as candidates for CI tolerance. GO enrichment analysis and KEGG pathway mapping linked CI tolerance to several phytohormones such as ABA, jasmonic acid and auxins and MAPK signaling among other pathways. Moreover, these results provide hints about the crosstalk between different phytohormones controlling CI tolerance and increases our current knowledge about the molecular pathways involved.
Chana-Muñoz, A., García, A., Aguado, E., Romero, J., Cebrián, G., Iglesias-Moya, J., Garrido, D., Cañizares, J., Valenzuela, J.L. and Jamilena, M. (2020). RNA-seq reveals molecular mechanisms behind chilling injury tolerance in ISW-treated zucchini fruit during cold storage. Acta Hortic. 1294, 149-154
DOI: 10.17660/ActaHortic.2020.1294.19
Cucurbita pepo, postharvest, chilling injury, RNA-seq

Acta Horticulturae