Transcriptome analysis provides insights into the role of phytohormones in regulating axillary bud development of flower stalk in Phalaenopsis

Abstract

• Exogenous application of diethyl aminoethyl hexanoate (DA-6) promotes ABFS development in Phalaenopsis. • The content of IAA, zeatin and GA3 was significantly affected during the development of the ABFS. • Differentially expressed genes related to hormone metabolism and signal transduction were identified through transcriptome analysis. • The hormonal signaling network plays an important role in regulating the outgrowth of axillary buds during DA-6 induced ABFS development. The inflorescence architecture of Phalaenopsis is determined by the development of the axillary buds of flower stalk (ABFS) in Phalaenopsis . Numerous studies have shown that plant hormones are the primary factors involved in the regulation of axillary bud development. However, the molecular mechanisms controlling how phytohormones regulate the development of ABFS in Phalaenopsis remain unknown. Here, we report that diethyl aminoethyl hexanoate (DA-6), a plant growth regulator, promotes ABFS development in Phalaenopsis 'Yen Shuai Red Grape'. The phytohormone contents were measured at five stages (bud length 0 cm (before axillary bud emergence), 0.5 cm, 1.0 cm, 1.5 cm, and 2.0 cm). We found that the GA 3 concentration increased gradually during DA-6-induced-ABFS development, whereas the IAA and ZA/ZT concentrations decreased from 0 cm to 1.0 cm. Then, we performed a comprehensive transcriptome study at five stages and the results showed that differentially expressed genes (DEGs) involved in plant hormone metabolism and signal transduction were significantly enriched at the early stage of ABFS development. Furthermore, we used weighted gene coexpression network analysis (WGCNA) to dissect the phytohormone regulatory network during DA-6-induced ABFS development. The turquoise module, which was positively correlated with GA 3 concentration and negatively related to zeatin concentration was identified and the genes involved in GA, CK, and SL metabolism and signal transduction were clustered in the turquoise module. In addition, the PhTB1 genes which encode integrators of diverse hormonal signaling networks were also found in the turquoise module. Collectively, our results provide novel insight into the mechanisms of DA-6-induced-ABFS development through the regulation of hormone metabolism/signal transduction and phytohormone regulatory networks.