Transcriptome analysis of harvested okra (Abelmoschus esculentus L.) in response to chilling stress

Abstract Okra ( Abelmoschus esculentus L.) is a novel vegetable with high nutritional and medicinal values. However, as a cold-sensitive crop, okra pods are susceptible to chilling injury (CI) during cold chain packaging and transportation, and the molecular mechanism of postharvest okra pods in response to chilling stress has not been elucidated. In this study, after storage at 4 °C for 15 d, okra pods from ‘Hokkaido’ exhibited progressively worseningCI symptoms, as well as continuously elevated CI index and CI incidence. Transcriptomic analysis showed that during low-temperature storage, many unigenes were activated by chilling stress and were mainly enriched in ‘Signal transduction’, ‘Amino acid metabolism’, and ‘Carbohydrate metabolism’. Further studies showed that the biosynthesis and signaling mechanism of ethylene (ETH) and abscisic acids (ABA) was activated by chilling stress, which induced reactive oxygen species (ROS) over-accumulation and up-regulated genes related to membrane lipid peroxidation. Chilling stress also activated genes involved in chlorophyll degradation and reduced chlorophyll a, chlorophyll b, and total chlorophyll content. In addition, 156 transcription factors (TFs) belonging to 12 families were identified from transcript databases. This study gained insight into the chilling transcriptional response mechanism of postharvest okra pods, which will contribute to cold chain management and molecular breeding of okra.