Comparative Transcriptome Analysis between Gynoecious and Monoecious Plants Identifies Regulatory Networks Controlling Sex Determination in Jatropha curcas

Abstract

Most germplasms of the biofuel plant Jatropha curcas are monoecious. A gynoecious genotype of J. curcas was found, whose male flowers are aborted at early stage of inflorescence development. To investigate the regulatory mechanism of transition from monoecious to gynoecious plants, a comparative transcriptome analysis between gynoecious and monoecious inflorescences were performed. A total of 3,749 genes differentially expressed in two developmental stages of inflorescences were identified. Among them, 32 genes were involved in floral development, and 70 in phytohormone biosynthesis and signaling pathways. Six genes homologous to KNOTTED1-LIKE HOMEOBOX GENE 6 (KNAT6), MYC2, SHI-RELATED SEQUENCE 5 (SRS5), SHORT VEGETATIVE PHASE (SVP), TERMINAL FLOWER 1 (TFL1), and TASSELSEED2 (TS2), which control floral development, were considered as candidate regulators that may be involved in sex differentiation in J. curcas. Abscisic acid, auxin, gibberellin, and jasmonate biosynthesis were lower, whereas cytokinin biosynthesis was higher in gynoecious than that in monoecious inflorescences. Moreover, the exogenous application of gibberellic acid (GA3) promoted perianth development in male flowers and partly prevented pistil development in female flowers to generate neutral flowers in gynoecious inflorescences. The arrest of stamen primordium at early development stage probably causes the abortion of male flowers to generate gynoecious individuals. These results suggest that some floral development genes and phytohormone signaling pathways orchestrate the process of sex determination in J. curcas. Our study provides a basic framework for the regulation networks of sex determination in J. curcas and will be helpful for elucidating the evolution of the plant reproductive system.

Differential gene expression analyses related to fruit yield of Jatropha curcas L. using RNA-seq

“…In the present study, JcGA2ox8 was upregulated, whereas the others (JcCLA1, JcFKF1, JcDMR6, JcTT4, JcCPD, JcEBF1, JcLOX3, JcLOX2 and JcCYP79B2) were mainly downregulated (Table 3). In a previous study, the exogenous application of GA could partially prevent pistil development in gynoecious Jatropha [4]. GA2ox8 could inhibit bioactive gibberellins to reduce their content [31].…”

“…Comparative transcriptome analysis is a better way to uncover the genetic mechanism responsible for fruit yield [3]. The genes involved in fruit yield could be identified using a comparative transcriptome analysis on contrasting materials [4]. In a previous study, 12084 ESTs have been reported in developing seeds of J. curcas [5].…”

“…In a previous study, 12084 ESTs have been reported in developing seeds of J. curcas [5]. In another empirical study, a comparative transcriptome analysis was performed between gynoecious and monoecious Jatropha, and 70 genes were detected and enriched in phytohormone biosynthesis and signalling pathways [4]. However, the information regarding transcriptome alterations associated with fruit yield in J. curcas remains scarce.…”

Flower-Specific Overproduction of Cytokinins Altered Flower Development and Sex Expression in the Perennial Woody Plant Jatropha curcas L.

“…J. curcas JcARR6, an orthologue of the cytokinin response gene ARR6 of Arabidopsis, is significantly upregulated in female compared with male flowers at the initial stage of flower development [32]. Moreover, the expression levels of the cytokinin biosynthetic genes JcIPT5, JcCYP735A1, and JcLOG5 were higher in gynoecious J. curcas with degenerated male flowers than in monoecious J. curcas [33].…”

“…J. curcas JcARR6, an orthologue of the cytokinin response gene ARR6 of Arabidopsis, is significantly upregulated in female compared with male flowers at the initial stage of flower development [32]. Moreover, the expression levels of the cytokinin biosynthetic genes JcIPT5, JcCYP735A1, and JcLOG5 were higher in gynoecious J. curcas with degenerated male flowers than in monoecious J. curcas [33].Because cytokinin is critical for pistil development [6,23], it is considered a major phytohormone responsible for expression of the female sex [34]. Therefore, the exogenous application of cytokinin is usually used to promote floral feminization in many plant species, such as Vitis vinifera [35], Spinacia oleracea [36], Mercurialis annua [37], Plukenetia volubilis [38], and Sapium sebiferum [39].…”