Carbohydrate and hormone regulatory networks driving dormancy release of Cardiocrinum giganteum (Wall.) Makino bulbs induced by low temperature

Bulb physiological dormancy significantly limits the development and utilization of Cardiocrinum giganteum (Wall.) Makino, a valuable medicinal, edible and ornamental plant. In the current study, to break the dormancy and reveal its mechanism, metabolome and transcriptome analyses using bulbs stored at 4°C for 0, 30, and 60 days (d) were conducted. Results revealed that bulb dormancy release and development were linked to hormones such as ABA, IAA, GA and ZR, as well as sucrose and starch. Total soluble sugars initially increased and then decreased within 60 days of low temperature treatment, contrary to the behaviour of starch content. Dormancy release predominantly relied on GA accumulation and ABA degradation. Additionally, genes involved in carbohydrate metabolism, including HK, SPS, BGLU, and SuSy, were up-regulated in the later stage. The energy production during carbohydrate metabolism mainly depended on the tricarboxylic acid cycle and glycolysis pathway. Hormone-mediated regulation and hormone signal transduction metabolism pathways were also obviously changed. Co-expression analysis indicated that key genes, such as NCED, PP2C and DELLA, related to the ABA signal transduction pathway, and GA2ox, ARF and SAUR, related to the IAA and GA signal transduction pathway, played a crucial role in dormancy release. Moreover, ZR signal transduction genes such as CRE, ARR-B, ARR-A and TRIT1 involved in cell division were up-regulated in bulbs treated at 4°C for 30 or 60 d. This study provides evidence for understanding the molecular mechanism underlying bulb dormancy release and is a guide for industry development and utilization of Cardiocrinum giganteum (Wall.) Makino.