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Authors: Jianhua Yue, Di Zhang, Guanqun Chen and Xiaohui Shen.
Scientia Horticulturae (2023)
Highlights • The main bioactive gibberellin controlling scape height in Agapanthus praecox is GA4. • ApGA20ox1 controls the biosynthesis of GA4 in Agapanthus praecox. • Suppression of ApGA20ox1 resulted in poor somatic embryogenesis potential in Agapanthus praecox. • ApGA20ox1 contributed to leaf elongation and plant height by affecting longitudinal cell length in Agapanthus praecox. • Suppression of ApGA20ox1 resulted in poor stress resistance traits in plant development of Agapanthus praecox.
Abstract: "Agapanthus praecox is cultivated worldwide as an ornamental plant, and a dwarf ideotype has become more popular due to its superior lodging resistance and its suitability for use in cut flowers. The main bioactive gibberellin (GA) controlling scape height in A. praecox is GA4. A GA biosynthesis gene, ApGA20ox1, controls GA4 biosynthesis in this species. Here, we report the development of an A. praecox dwarf phenotype, which was generated by targeted suppression of the biosynthetic pathway for GAs. We utilized Agrobacterium-mediated genetic transformation using embryogenic callus with RNA interference (RNAi) to selectively reduce the expression of the ApGA20ox1 gene. Interestingly, suppression of ApGA20ox1 resulted in poor somatic embryogenesis potential in A. praecox, which was accompanied by a higher accumulation of hydrogen peroxide and poorer catalase activity. Subsequently, the RNAi plantlets showed lower GA levels, leading to inhibition of cell longitudinal size in leaves, which reduced plant height. Furthermore, the dwarf (RNAi) plantlets accumulated higher levels of saccharides and plant hormones such as indole acetic acid (IAA) and abscisic acid (ABA) than the wild type accumulated. However, the levels of endogenous hormones such as GAs, brassinosteroids (BRs), cytokinins (CTKs), which respond to cell proliferation and cell expansion, were significantly decreased. Isobaric tags for relative and absolute quantification (iTRAQ) proteomics revealed that differentially accumulated proteins (DAPs) were enriched differently between control and RNAi plantlets in the categories of cell wall, hormone metabolism, carbohydrate metabolism and stress response. This study provides new insights into the role of GAs in the process of somatic embryogenesis and plant height control in A. praecox."
