Effect of Exogenous Gibberellin, Paclobutrazol, Abscisic Acid, and Ethrel Application on Bulblet Development in Lycoris radiata

Abstract

Lycoris species have great ornamental and medicinal values; however, their low regeneration efficiency significantly restricts their commercial production. Exogenous hormone application is an effective way to promote bulblet development, but their effect on Lycoris radiata has not been verified to date. In the present study, we examined the effect of different exogenous hormones on bulblet development in L. radiata, and found that gibberellic acid (GA) significantly inhibited, whereas paclobutrazol (PBZ), abscisic acid (ABA), and ethrel promoted bulblet development, especially PBZ, a GA biosynthesis inhibitor. Furthermore, GA reduced endogenous cytokinin (CK) content, as well as the activities of carbohydrate metabolism enzymes, including sucrose synthase (SUS) and glucose-1-phosphate adenylyltransferase (AGPase), by downregulating the expression levels of LrSUS1, LrSUS2, and genes encoding AGPase large and small subunits. This resulted in the decrease in carbohydrate accumulation in the bulblets, thus hindering their development. PBZ had the opposite effect to GA on carbohydrate metabolism; it decreased endogenous GA15 and GA24, thereby promoting bulblet development. ABA promoted endogenous auxin content and the activities of starch synthesis enzymes, especially soluble starch synthase (SSS) and granule-bound SS (GBSS), through the up-regulation of the expression levels of LrSS1, LrSS2, and LrGBSS1 genes, which could also result in the accumulation of carbohydrates in the bulblets and promote their development. In addition, ethrel application partly promoted bulblet development by promoting endogenous CK content. Although the accumulation of carbohydrates and the activity of starch enzymes were increased by ethrel treatment, we hypothesized that the effect of ethrel on regulating carbohydrate metabolism may be indirect. Our results could provide a basis for improving the propagation efficiency of L. radiata for production, as well as propose some directions for future research.

Exogenous DCPTA Treatment Increases Mung Bean Yield by Improving Carbon Metabolism Pathway and Up-Regulating Photosynthetic Capacity and Antioxidants

“…Kinetin is an unnatural cytokinin to improve plant stress resistance and delays aging (Nesmith et al, 2005 ; Lukatkin et al, 2007 ). These and other growth regulators have been applied to various crops (Oshanova et al, 2021 ; Wang J. et al, 2021 ; Xu et al, 2021 ).…”

Early Sucrose Degradation and the Dominant Sucrose Cleavage Pattern Influence Lycoris sprengeri Bulblet Regeneration In Vitro

“…In contrast, we found that an initial relatively low level of ABA might be favorable for effective bulblet regeneration in vitro. This difference might result from the different first sampling time points (3 d after cross-cutting by Xu (2021) [ 33 ] versus 1 d in this study), indicating that the changes in endogenous hormones are rapid and significant regarding regulation during the competence stage (0–1 d). ZR is the most abundant CK in plants [ 34 ], exhibiting cell division and meristematic activities during plant growth and development.…”

“…Exogenous hormone application is an effective way to promote bulblet development. Xu (2021) examined the effect of different exogenous hormones on bulblet development in L. radiata ex vitro and reported that GA significantly inhibited bulblet development, whereas paclobutrazol (PBZ), ABA, and Ethrel had positive effects [ 33 ]. In contrast, we found that an initial relatively low level of ABA might be favorable for effective bulblet regeneration in vitro.…”

“…Previous studies indicated that sucrose metabolism holds a central position for bulblet formation and development; for instance, the formation of bulblets in Lilium and Lycoris was accompanied by the significant upregulation of sucrose catabolism-related enzyme genes and the sharp decline of sucrose content in mother scales [ 11 , 17 , 33 ]. In addition, sucrose has also been reported to act as signaling molecule instead of an osmotic pressure regulator and carbon source during bulblet induction and expansion in Lilium sargentiae [ 10 ].…”

“…BA is the most commonly used exogenous CK in Lycoris tissue culture, and it is generally believed that the addition of BA within a certain range is conducive to promoting the occurrence of bulblets [7,31,32]. The positive role of BA in promoting the average proliferation numbers of bulblets has also been reported under ex vitro conditions in L. radiata [33]. To further clarify why the addition of BA can significantly promote the incidence of bulblets, we artificially constructed different bulblet incidence systems by adjusting the BA concentration in media.…”