Abstract
BackgroundJatropha curcas L. is a potential biofuel plant. Application of exogenous cytokinin (6-benzyladenine, BA) on its inflorescence buds can significantly increase the number of female flowers, thereby improving seed yield. To investigate which genes and signal pathways are involved in the response to cytokinin in J. curcas inflorescence buds, we monitored transcriptional activity in inflorescences at 0, 3, 12, 24, and 48 h after BA treatment using a microarray.ResultsWe detected 5,555 differentially expressed transcripts over the course of the experiment, which could be grouped into 12 distinct temporal expression patterns. We also identified 31 and 131 transcripts in J. curcas whose homologs in model plants function in flowering and phytohormonal signaling pathways, respectively. According to the transcriptional analysis of genes involved in flower development, we hypothesized that BA treatment delays floral organ formation by inhibiting the transcription of the A, B and E classes of floral organ-identity genes, which would allow more time to generate more floral primordia in inflorescence meristems, thereby enhancing inflorescence branching and significantly increasing flower number per inflorescence. BA treatment might also play an important role in maintaining the flowering signals by activating the transcription of GIGANTEA (GI) and inactivating the transcription of CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) and TERMINAL FLOWER 1b (TFL1b). In addition, exogenous cytokinin treatment could regulate the expression of genes involved in the metabolism and signaling of other phytohormones, indicating that cytokinin and other phytohormones jointly regulate flower development in J. curcas inflorescence buds.ConclusionsOur study provides a framework to better understand the molecular mechanisms underlying changes in flowering traits in response to cytokinin treatment in J. curcas inflorescence buds. The results provide valuable information related to the mechanisms of cross-talk among multiple phytohormone signaling pathways in woody plants.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-014-0318-z) contains supplementary material, which is available to authorized users.
Highlights
Jatropha curcas L. is a potential biofuel plant
To elucidate the mechanism underlying this response, we performed a transcriptional analysis of J. curcas inflorescence buds after BA treatment. 5,555 differentially expressed transcripts were identified, which could be grouped into 12 clusters representing distinct regulatory patterns and belonged to 32 gene ontology categories
Based on our analysis of genes involved in flowering and phytohormone signaling pathways, we hypothesized that BA application increased flower number by activating the transcription of genes that initiate flowering and repressing that of genes involved in the formation of floral organs
Summary
Jatropha curcas L. is a potential biofuel plant. Application of exogenous cytokinin (6-benzyladenine, BA) on its inflorescence buds can significantly increase the number of female flowers, thereby improving seed yield. Cytokinins are involved in many important aspects of plant growth and development, e.g. promoting vascular cambium activity, controlling organ development, and regulating shoot and root branching, as well as responding to biotic and abiotic stresses [9,10,11]. They play important roles in maintaining the activity and function of the shoot apical meristem (SAM) [9,12]. A number of genes, such as SHOOT MERISTEMLESS (STM), WUSCHEL (WUS), CLAVATA (CLV), LONELY GUY (LOG), AINTEGUMENTA (ANT), ANT-like 6 (AIL6), ANT-like 7 (AIL7), are involved in this process [14,15,16,17,18,19,20,21,22]
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