Transcriptomic analyses of carvone inhibited sprouting in sweet potato (Ipomoea batatas (L.) Lam cv ‘Yan 25′) storage roots

Sprouting is an important postharvest problem in the transport and storage of sweet potato. This study investigated the effect of carvone fumigation on the development of sprouts in 'Yan 25′ sweet potato storage roots and sprouts. The results showed that visible buds could be observed in untreated root after 4 d at 30 ℃, however no buds were found on carvone treated sweet potato, even after 14 d storage. The levels of β-amylase activity were lower in the carvone treated roots and were associated with higher starch content. Treatment of sweet potato sprouts with carvone severely damaged the sprouts after 24 h and finally turned black after 72 h treatment, resulting in higher MDA content. The transcriptomic analyses showed that the manipulation of auxin distribution, cytokinin metabolism, cell wall synthesis and cell wall loosening processes were associated with carvone inhibition of sprouting in sweet potato roots. Further transcriptomic analyses on sweet potato sprouts revealed a similar transcription profile except that the gibberellin metabolism was also affected in the sprouts by carvone treatment. The up-regulation of apoptosis related genes in carvone treated sprouts, included UDP-D-apiose/UDP-D-xylose synthase (UAXS), ACC oxidase (ACO), tonoplast intrinsic protein (TIP), respiratory burst oxidase (RBOH), senescence associated gene (SAG) which were correlated with the lethal effect of carvone on the sprout. Two conceptual models elucidating the molecular mechanism of carvone inhibited sprouting in sweet potato are proposed. The further elucidation of this mechanism will potentially lead to a theory to optimize the method in sprouting inhibition of sweet potato.