Abstract
BackgroundLycoris species have great ornamental and medicinal values; however, their low regeneration efficiency seriously restricts their commercial production. Understanding the mechanism of bulblet propagation in this genus, which has remained underexplored to date, could provide a theoretical basis for improving the reproductive efficiency. Therefore, we studied the bulblet initiation and developmental processes in Lycoris radiata.ResultsWe found that bulblets are formed on the junctions of the innermost layers of scales and the basal plate, and initially present as an axillary bud and gradually develop into a bulblet. We also determined the changes in carbohydrate and endogenous hormone contents during bulblet initiation and development, as well as the expression patterns of genes involved in carbohydrate metabolism and hormone biosynthesis and signaling through transcriptome analysis. Soluble sugars derived from starch degradation in the outer scales are transported to and promote bulblet initiation and development through starch synthesis in the inner scales. This process is mediated by several genes involved in carbohydrate metabolism, especially genes encoding ADP glucose pyrophosphorylase, a crucial starch synthesis enzyme. As for hormones, endogenous IAA, GA, and ABA content showed an increase and decrease during bulblet initiation and development, respectively, which were consistent with the expression patterns of genes involved in IAA, GA, and ABA synthesis and signal transduction. In addition, a decrease in ZR content may be down- and up-regulated by CK biosynthesis and degradation related genes, respectively, with increasing auxin content. Furthermore, expression levels of genes related to BR, JA, and SA biosynthesis were increased, while that of ethylene biosynthesis genes was decreased, which was also consistent with the expression patterns of their signal transduction genes.ConclusionsThe present study provides insights into the effect of carbohydrate metabolism and endogenous hormone regulation on control of L. radiata bulblet initiation and development. Based on the results, we propose several suggestions to improve L. radiata propagation efficiency in production, which will provide directions for future research.
Highlights
Lycoris species have great ornamental and medicinal values; their low regeneration efficiency seriously restricts their commercial production
Morphological description of bulblet initiation and development in Lycoris radiata Based on a two-month observation of bulblet formation in sections prepared from L. radiata bulbs collected from the experimental base at the Shanghai Academy of Agricultural Sciences, the process of bulblet formation can be divided into two stages: bulblet initiation (0–7 days after treatment (DAT)) and bulblet development (7–60 Days after treatment (DAT))
differentially expressed genes (DEGs) related to hormone biosynthesis and signal transduction We identified numerous DEGs related to the synthesis and signal transduction of hormones, including Indole-3-acetic acid (IAA), CK, gibberellic acid (GA), abscisic acid (ABA), BR, jasmonic acid (JA), and ethylene, during bulblet initiation and development
Summary
Lycoris species have great ornamental and medicinal values; their low regeneration efficiency seriously restricts their commercial production. Lycoris species have high ornamental value and display an exceptionally wide diversity of flower colors [2]. They have high medicinal value, and alkaloids isolated from their bulbs inhibit viruses, inflammation, tumors, and cancers [3, 4]. This genus has great potential for commercial development. Bulblet differentiation is regulated by several factors in the study of other flowering bulbs, including carbohydrate metabolism and endogenous hormone regulation [7,8,9], which has remained underexplored in Lycoris to date
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