Comparative Physiological and Transcriptomic Analyses Reveal the Actions of Melatonin in the Delay of Postharvest Physiological Deterioration of Cassava

Abstract

Melatonin plays important roles in various aspects of biological processes. However, it is less known on the effects and mechanism of melatonin on the postharvest physiological deterioration (PPD) process of cassava, which largely restricts the potential of cassava as a food and industrial crop. In this study, we found that exogenous application of melatonin significantly delayed PPD of cassava tuberous roots by reducing H2O2 content and improving activities of catalase and peroxidase. Moreover, 3425 differentially expressed genes by melatonin during the PPD process were identified by transcriptomic analysis. Several pathways were markedly affected by melatonin treatments, including metabolic-, ion homeostasis-, and enzyme activity-related processes. Further detailed analysis revealed that melatonin acted through activation of ROS-scavenging and ROS signal transduction pathways, including antioxidant enzymes, calcium signaling, MAPK cascades, and transcription factors at early stages. Notably, the starch degradation pathway was also activated at early stages, whereas it was repressed by melatonin at middle and late stages, thereby indicating its regulatory role in starch metabolism during PPD. Taken together, this study yields new insights into the effect and underlying mechanism of melatonin on the delay of PPD and provides a good strategy for extending shelf life and improvement of cassava tuberous roots.

Proteomic analysis of injured storage roots in cassava (Manihot esculenta Crantz) under postharvest physiological deterioration

“…(2016) [31]. Ascorbic peroxidase (APX) activity was measured following the commercial assay kit (Beijing Solarbio Technology Company, China) according to the supplier’s protocol.…”

Melatonin redirects carbohydrates metabolism during sugar starvation in plant cells

“…Moreover, the most of genes involved in starch degradation, such as starch phosphorylase, α-amylase and β-amylase, were induced. 51 It clearly shows that melatonin may be a regulator of carbohydrates metabolism, including starch.…”

“…On the one hand, recently Kostopoulou et al 50 have revealed that exogenous melatonin combined with ascorbic acid enhanced adaptation of Citrus aurantium L. seedlings to salinity stress, which was accompanied by increase in the total carbohydrates and proline concentrations. On the other hand, Hu et al 51 showed that genes related to starch synthesis were repressed by melatonin during the postharvest physiological deterioration process of cassava. It was mainly: sucrose synthase, glucose phosphomutase and ADPglucose pyrophosphorylase.…”

Effects of Calcium and Magnesium Fertilization on Antioxidant Activities during Cassava Postharvest Physiological Deterioration

“…The supernatant was collected to determine the activity of each enzyme using spectrophotometric diagnostic kits (Nanjing Jiancheng Bioengeneering Institute) in three replicates. The activities of SOD and POD were detected according to the manufacturer's instructions, as described by Hu et al (2016).…”

“…The homogenate was centrifuged at 2500 rpm for 10 min at 25°C. The supernatant was collected to evaluate the activity of the enzyme using kits (Nanjing Jiancheng Bioengeneering Institute) according to the manufacturer's instructions, as described by Hu et al (2016).…”