Abstract:Using Mikania micrantha cutted and planted in Mengxiu forest farm of Ruili City, Yunnan Province as test materials, we quantitatively analyzed the contents of indole-3-acetic acid (IAA), gibberellins (GAs), abscisic acid (ABA), trans-zeatin (tZ), N6-Isopentenyladenine (IP), 1-aminocyclopropanecarboxylic acid (ACC), jasmonic acid (JA) and salicylic acid (SA) in flower buds at the undifferentiated stage of flower buds and the differentiation stage of inflorescence primordium by liquid chromatography mass spectrometry (LC-MS/MS). Based on the transcriptome gene function annotation data, we also analyzed the expression of genes related to endogenous hormone synthesis, metabolism and signal transduction pathways. The aim of this study was to explore the regulatory effects of different endogenous hormones on flower bud formation of M. micrantha, and analyze the mechanism of endogenous hormone synthesis and signal transduction pathway related genes regulating flower bud differentiation of M. micrantha. It provides theoretical and technical support for controlling the sexual reproduction of M. micrantha by regulating the endogenous hormone level of M. micrantha with exogenous hormones in the later stage. The results showed that: (1) the contents of GA15, GA19, GA20, GA24, IAA, ABA and ACC in flower bud at undifferentiated stage were lower than those at inflorescence primordium differentiation stage, while the contents of tZ and IP in flower bud at undifferentiated stage were significantly higher than those at inflorescence primordium differentiation stage. (2) Based on RNA-seq results, a total of 7 116 differentially expressed genes (DEGs) were obtained at two flower bud differentiation stages of M. micrantha, of which 3 907 were up-regulated and 3 209 were down regulated. (3) In terms of endogenous hormone synthesis, a large number of DEGs involved in the synthesis of GA15, GA19, GA20, GA24, IAA, ABA and ACC were up-regulated during inflorescence primordium differentiation, which was consistent with their high content trend during inflorescence primordium differentiation of M. micrantha. The high expression of YUUCA gene family involved in IAA synthesis and ACS gene involved in ETH at inflorescence primordium differentiation stage may also be involved in promoting flower bud differentiation of M. micrantha. (4) In the plant hormone transduction pathways, flower bud differentiation of M. micrantha was regulated by down-regulation of AUX/IAA gene (gene-E3N88_07743) and up-regulation of ARF (gene-E3N88_41119) in auxin signal transduction pathway, up-regulation of ERF (gene-E3N88_41547) in ethylene signal transduction pathway, up-regulation of GID1 (gene-E3N88_19448) in gibberellin signal transduction pathway, down-regulation by B-ARR (Gene-E3N88_28086) and A-RRR (gene-E3N88_40764) in cytokinin signal transduction pathway, up-regulation of AREB (gene-E3N88_18558) in abscisic acid signal transduction pathway, up-regulation of JAZ (gene-E3N88_05628) and down-regulation of MYC2 (gene-E3N88_32405) in jasmonic acid signal transduction pathway. Therefore, high levels of GA15, GA19, GA20, GA24, IAA, ABA and ETH are conducive to flower bud differentiation of M. micrantha. The flower bud differentiation process of M. micrantha regulates the hormone concentration by changing the expression of different kinds of endogenous hormone synthesis and metabolism genes, and the hormone causes the expression of downstream genes through signal transduction pathway to regulate the flower bud differentiation of M. micrantha.