Table_6_Changes and transcriptome regulation of endogenous hormones during somatic embryogenesis in Ormosia henryi Prain.xls

IntroductionOrmosia henryi is a rare and endangered plant growing in southern China. Somatic embryo culture is an effective measure for the rapid propagation of O. henryi. It has not been reported how regulatory genes induce somatic embryogenesis by regulating endogenous hormone changes during the process of somatic embryogenesis in O. henryi.
MethodsIn this study, we analysed the endogenous hormone levels and transcriptome data of nonembryogenic callus (NEC), embryogenic callus (EC), globular embryo (GE) and cotyledon embryo (CE) in O. henryi.
ResultsThe results showed that the indole-3-acetic acid (IAA) content was higher and the cytokinins (CKs) content was lower in EC than in NEC, and the gibberellins (GAs) and abscisic acid (ABA) contents were significantly higher in NEC than in EC. The contents of IAA, CKs, GAs and ABA increased significantly with EC development. The expression patterns of differentially expressed genes (DEGs) involved in the biosynthesis and signal transduction of auxin (AUX) (YUCCA and SAUR), CKs (B-ARR), GAs (GA3ox, GA20ox, GID1 and DELLA) and ABA (ZEP, ABA2, AAO3, CYP97A3, PYL and ABF) were consistent with the levels of endogenous hormones during somatic embryogenesis (SE). In this study, 316 different transcription factors (TFs) regulating phytohormones were detected during SE. AUX/IAA were downregulated in the process of EC formation and GE differentiation into CE, but other TFs were upregulated and downregulated.
ConclusionTherefore, we believe that relatively high IAA content and low CKs, GAs and ABA contents contribute to EC formation. The differential expression of AUX, CKs, GAs and ABA biosynthesis and signal transduction genes affected the endogenous hormone levels at different stages of SE in O. henryi. The downregulated expression of AUX/IAA inhibited NEC induction, promoted EC formation and GE differentiation into CE.

**引言** 花榈木（Ormosia henryi）是中国南方分布的珍稀濒危植物。体细胞胚培养是实现花榈木快速繁育的有效手段，但目前尚未有研究阐明，在花榈木体细胞胚发生过程中，调控基因如何通过调控内源激素水平变化来诱导体细胞胚形成。

**方法** 本研究对花榈木的非胚性愈伤组织（nonembryogenic callus, NEC）、胚性愈伤组织（embryogenic callus, EC）、球形胚（globular embryo, GE）与子叶胚（cotyledon embryo, CE）开展了内源激素水平检测与转录组数据分析。

**结果** 结果显示，胚性愈伤组织（EC）中的吲哚-3-乙酸（indole-3-acetic acid, IAA）含量高于非胚性愈伤组织（NEC），而细胞分裂素（cytokinins, CKs）含量则低于NEC；此外，NEC中的赤霉素（gibberellins, GAs）与脱落酸（abscisic acid, ABA）含量均显著高于EC。随着EC的发育进程，IAA、CKs、GAs与ABA的含量均显著上升。参与生长素（auxin, AUX）生物合成与信号转导的差异表达基因（differentially expressed genes, DEGs），包括YUCCA与SAUR；细胞分裂素相关的B-ARR；赤霉素相关的GA3ox、GA20ox、GID1与DELLA；以及脱落酸相关的ZEP、ABA2、AAO3、CYP97A3、PYL与ABF，其表达模式与花榈木体细胞胚发生（somatic embryogenesis, SE）过程中的内源激素水平变化趋势一致。本研究共在SE过程中鉴定出316个调控植物激素的转录因子（transcription factors, TFs）。AUX/IAA家族基因在EC形成以及GE向CE分化的过程中均呈现下调表达，其余转录因子则呈现上调或下调的动态表达模式。

**结论** 综上，本研究认为较高的IAA含量与较低的CKs、GAs及ABA含量，有利于EC的形成。生长素、细胞分裂素、赤霉素与脱落酸的生物合成及信号转导相关基因的差异表达，调控了花榈木SE不同阶段的内源激素水平。AUX/IAA家族基因的下调表达，可抑制NEC的诱导过程，同时促进EC形成以及GE向CE分化。