Elucidating Biological Functions of 9-cis-Epoxycarotenoid Dioxygenase Genes Involved in Seed Dormancy in Paeonia lactiflora

Abstract

Abscisic acid (ABA) is a major phytohormone affecting seed dormancy and germination in plants. ABA is synthesized mainly through the C40 carotenoid pathway. In the ABA biosynthesis pathway, 9-cis-epoxycarotenoid dioxygenase (NCED) is a key rate-limiting enzyme that regulates the accumulation and content of ABA. However, the role of the NCED gene in perennial plants with complex seed dormancy remains largely unknown. Here, we cloned two differentially expressed paralogs of herbaceous peony NCED genes, named PlNCED1 and PlNCED2, and further identified their involvement in seed dormancy from perennial herbaceous peony experiencing complex double seed dormancy. The deduced PlNCED amino acid sequences had high sequence homology with NCED sequences from other plants and contained the typical conserved RPE65 domain of the NCED family. Phylogenetic analysis showed that PlNCED1 and PlNCED2 have a close relationship with PoNCED in Paeonia ostii and VvNCED6 in Vitis vinifera, respectively. A subcellular localization assay demonstrated that the PlNCED1 protein resided within the nucleus, while the PlNCED2 protein was located in the cytoplasm, indicating their different roles in the biosynthesis of ABA. Furthermore, the content of endogenous ABA in transgenic calluses showed that PlNCEDs were positively correlated with ABA content. Both PlNCED transgenic Arabidopsis lines and the functional complementation of Arabidopsis NCED mutants found that PlNCEDs promoted seed dormancy and delayed seed germination. These results reveal that PlNCEDs participate in the seed dormancy of herbaceous peony by regulating the accumulation of endogenous ABA.

Molecular Biology of Ornamental Plants

“…Fei et al identified and cloned two genes from the NCED family in Paeonia lactiflora, which are related to ABA synthesis in the herbaceous peony, named PlNCED1 and PlNCED2. Further studies confirmed the function of the PlNCED gene in inducing seed dormancy and hindering seed germination [4]. In iris plants, Wang et al confirmed the function of the AP2/ERF superfamily member IlAP2, which interacts with IlMT2a, in enhancing Cd tolerance [5].…”

Genome-wide identification and in-silico expression analysis of carotenoid cleavage oxygenases gene family in Oryza sativa (rice) in response to abiotic stress

“…The identification of the NCED gene marked a significant milestone in advancing our comprehension of ABA production and its role in plant growth and development. The NCED gene was initially cloned in the maize ABA-deletion mutant Vp14, leading to a better understanding of NCED's involvement in ABA synthesis (Fei et al, 2023). Further research in Arabidopsis revealed nine CCOs genes, five of which (AtNCED2, AtNCED3, AtNCED5, AtNCED6, and AtNCED9) are involved in ABA synthesis (Hu et al, 2021).…”

A mulberry 9-cis-epoxycarotenoid dioxygenase gene MaNCED1 is involved in plant growth regulation and confers salt and drought tolerance in transgenic tobacco

“…Overexpression of NCED promotes ABA accumulation and delays seed germination (Wang et al, 2011), which is consistent with the results of this study. Previous reports indicate that ABA controls root elongation by regulating auxin biosynthesis, distribution and transport (Chen et al, 2016;Fei et al, 2023). High concentrations of exogenous auxin inhibit seed germination in A. thaliana, while low concentrations promote seed germination (He et al, 2012).…”