Flavonoid accumulation modulates the responses of cassava tuberous roots to postharvest physiological deterioration

Postharvest physiological deterioration (PPD) caused by wounding is one of the main constraints that affect the development of cassava industry. However, the molecular mechanisms underlying the PPD are unknown. In the present study the adaptive response to wound stress was analyzed in combination with transcriptome and metabolome in four kinds of PPD phenomenon from cassava tuberous roots. The results indicated that starch, β-carotene, (-)-epigallocatechin, cyanidin-3-O-glucoside, and L-epicatechin were altered in the wounded tuberous roots. Moreover, the ROS scavenging system was activated at the PPD preliminary stage. Transcriptome analysis further showed that the strongly induced genes were mainly related to carbohydrate metabolism, signal transduction, and polyketide metabolism. Twenty-eight differentially expressed genes (DEGs) in the flavonoid pathway were preferably enriched. The relative quantitative analysis of seventeen genes demonstrated that they were responsive to PPD. Fifty-one differential flavonoid metabolites were detected in widely targeted metabolome profile, among which, luteolin, kaempferol, (-) epicatechin, phloretin, and naringenin were enhanced during PPD. The virus-induced gene silencing of MeCHS3 and MeANR showed that tuberous roots changed tolerance to PPD, and the total flavonoid and anthocyanin contents in leaves were changed. Therefore, the candidate genes and metabolites in flavonoid pathways could participate in PPD regulation. In addition, a proposed model was generated to elaborate the response mechanism of flavonoids under wounding stress, thus providing a future direction for breeding PPD-tolerant cultivars of cassava.