CAS Key Laboratory of Tropical Plant Resources and Sustainable Use, Xishuangbanna Tropical Botanical Garden, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Menglun, Mengla, 666303, Yunnan, China.
Center of Economic Botany, Core Botanical Gardens, Chinese Academy of Sciences, Menglun, Mengla, 666303, Yunnan, China.
BMC Plant Biol. 2019 Nov 4;19(1):468. doi: 10.1186/s12870-019-2069-3.
In higher plants, inflorescence architecture is an important agronomic trait directly determining seed yield. However, little information is available on the regulatory mechanism of inflorescence development in perennial woody plants. Based on two inflorescence branching mutants, we investigated the transcriptome differences in inflorescence buds between two mutants and wild-type (WT) plants by RNA-Seq to identify the genes and regulatory networks controlling inflorescence architecture in Jatropha curcas L., a perennial woody plant belonging to Euphorbiaceae.
Two inflorescence branching mutants were identified in germplasm collection of Jatropha. The duo xiao hua (dxh) mutant has a seven-order branch inflorescence, and the gynoecy (g) mutant has a three-order branch inflorescence, while WT Jatropha has predominantly four-order branch inflorescence, occasionally the three- or five-order branch inflorescences in fields. Using weighted gene correlation network analysis (WGCNA), we identified several hub genes involved in the cytokinin metabolic pathway from modules highly associated with inflorescence phenotypes. Among them, Jatropha ADENOSINE KINASE 2 (JcADK2), ADENINE PHOSPHORIBOSYL TRANSFERASE 1 (JcAPT1), CYTOKININ OXIDASE 3 (JcCKX3), ISOPENTENYLTRANSFERASE 5 (JcIPT5), LONELY GUY 3 (JcLOG3) and JcLOG5 may participate in cytokinin metabolic pathway in Jatropha. Consistently, exogenous application of cytokinin (6-benzyladenine, 6-BA) on inflorescence buds induced high-branch inflorescence phenotype in both low-branch inflorescence mutant (g) and WT plants. These results suggested that cytokinin is an important regulator in controlling inflorescence branching in Jatropha. In addition, comparative transcriptome analysis showed that Arabidopsis homologous genes Jatropha AGAMOUS-LIKE 6 (JcAGL6), JcAGL24, FRUITFUL (JcFUL), LEAFY (JcLFY), SEPALLATAs (JcSEPs), TERMINAL FLOWER 1 (JcTFL1), and WUSCHEL-RELATED HOMEOBOX 3 (JcWOX3), were differentially expressed in inflorescence buds between dxh and g mutants and WT plants, indicating that they may participate in inflorescence development in Jatropha. The expression of JcTFL1 was downregulated, while the expression of JcLFY and JcAP1 were upregulated in inflorescences in low-branch g mutant.
Cytokinin is an important regulator in controlling inflorescence branching in Jatropha. The regulation of inflorescence architecture by the genes involved in floral development, including TFL1, LFY and AP1, may be conservative in Jatropha and Arabidopsis. Our results provide helpful information for elucidating the regulatory mechanism of inflorescence architecture in Jatropha.
在高等植物中，花序结构是一个重要的农艺性状，直接决定着种子的产量。然而，关于多年生木本植物花序发育的调控机制，人们知之甚少。本研究基于两个花序分枝突变体，通过 RNA-Seq 比较了突变体和野生型（WT）植物的花序芽中的转录组差异，以鉴定控制麻疯树（Jatropha curcas L.）花序结构的基因和调控网络，麻疯树是大戟科的一种多年生木本植物。
在麻疯树种质资源库中鉴定出两个花序分枝突变体。 duo xiao hua（dxh）突变体具有七序分支花序，gynoecy（g）突变体具有三序分支花序，而 WT 麻疯树主要具有四序分支花序，田间偶尔出现三序或五序分支花序。通过加权基因相关网络分析（WGCNA），我们从与花序表型高度相关的模块中鉴定出了几个参与细胞分裂素代谢途径的枢纽基因。其中，麻疯树腺苷激酶 2（JcADK2）、腺嘌呤磷酸核糖基转移酶 1（JcAPT1）、细胞分裂素氧化酶 3（JcCKX3）、异戊烯基转移酶 5（JcIPT5）、LONELY GUY 3（JcLOG3）和 JcLOG5 可能参与了麻疯树中的细胞分裂素代谢途径。同样，细胞分裂素（6-苄基腺嘌呤，6-BA）在花序芽上的外源应用诱导了低分枝突变体（g）和 WT 植物中的高分枝花序表型。这些结果表明细胞分裂素是控制麻疯树花序分枝的重要调节剂。此外，比较转录组分析表明，拟南芥同源基因麻疯树 AGAMOUS-LIKE 6（JcAGL6）、JcAGL24、FRUITFUL（JcFUL）、LEAFY（JcLFY）、SEPALLATAs（JcSEPs）、TERMINAL FLOWER 1（JcTFL1）和 WUSCHEL-RELATED HOMEOBOX 3（JcWOX3）在 dxh 和 g 突变体与 WT 植物的花序芽中差异表达，表明它们可能参与了麻疯树的花序发育。JcTFL1 的表达下调，而 JcLFY 和 JcAP1 的表达上调在低分枝 g 突变体的花序中。
细胞分裂素是控制麻疯树花序分枝的重要调节剂。参与花发育的基因（包括 TFL1、LFY 和 AP1）对花序结构的调节在麻疯树和拟南芥中可能是保守的。我们的研究结果为阐明麻疯树花序结构的调控机制提供了有价值的信息。
