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Molecular Characterization and Expression of Ethylene Biosynthetic Genes During Cut Flower Development in Tree Peony (Paeonia suffruticosa) in Response to Ethylene and Functional Analysis of PsACS1 in Arabidopsis thaliana

Zhou, Lin, Zhang, Chao, Fu, Jianxin, Liu, Miao, Zhang, Yuhuan, Wang, Yanjie, Dong, Li
Journal of plant growth regulation 2013 v.32 no.2 pp. 362-375
1-methylcyclopropene, Arabidopsis thaliana, Northern blotting, Paeonia suffruticosa, complementary DNA, corolla, cut flowers, ethylene, ethylene production, flowering, gene overexpression, genes, hypocotyls, leaves, trees, vase life
Our previous studies have suggested that ethylene is likely to be involved in the regulation of opening and senescence of cut flowers of tree peony. In the present work, to understand the molecular regulation of ethylene biosynthesis in cut tree peony flower development, we isolated two full-length cDNAs encoding ethylene synthetic enzymes, termed PsACS1 and PsACO1, from tree peony flower petals and investigated the effects of exogenous ethylene and 1-methylcyclopropene (1-MCP) on their expressions during vase life. Northern blot analysis revealed that in untreated flowers slight expression of PsACS1 was initiated until flowers half opened and reached the maximum when flowers fully opened, whereas PsACO1 exhibited constitutive levels during flower opening. PsACS1 expression was substantially induced by ethylene and inhibited by 1-MCP during flower development, and no significant alteration was found in the accumulation of PsACO1 transcript in the petals of differently treated flowers. These results suggest that the PsACS1 gene and its resultant protein may be involved in flower opening and senescence, whereas PsACO1 seems constitutively expressed in tree peony. Via Agrobacterium-mediated transformation, PsACS1 was successfully inserted into Arabidopsis and T3 transgenic lines were used for functional analysis of PsACS1. Compared with the wild-type control, PsACS1-overexpressing plants showed a discrepant phenotype, including shorter hypocotyls, fewer leaves, smaller rosette diameter, and later flowering, which were all attributed to the higher ethylene production caused by the ectopic expression of PsACS1 in Arabidopsis. This result provides support of the hypothesis that PsACS1 is an important gene involved in ethylene biosynthesis during cut flower opening and senescence of tree peony.