Abstract Detail

Development and Structure

Ho, Yi-Wen [1], Chang, JenYu [2], Liao, Pei-Chun [3], Wu, Cheng-Chiang [1], Wang, Chun-Neng [1].

Determinate to be indeterminate: Diversification of meristem gene regulatory network between sexual and asexual reproduction in Titanotrichum (Gesnariaceae).

Reproduction is pivotal to successful adaptation of plants. While sexual reproduction that requires determinate sex organs (e.g., flowers and inflorescences) prevails in angiosperms, floral reversion (i.e., floral meristems reverse to vegetative meristems) was evolved independently in diverse angiosperm families (e.g., Brassicaceae, Bromeliaceae, Gesnariaceae, Liliaceae, Ranunculaceae, and Saxifragaceae). In Arabidopsis, WUSCHEL (WUS) encodes a homeobox transcription factor that promotes gene expression of the MADS-box gene AGAMOUS (AG) for determination of floral meristem (FM). In return, AG represses the WUS expression. WUS also regulates the maintenance of stem cell niche in shoot apical and axillary meristems (SAM and AM). The KNOX gene SHOOT MERISTEMLESS (STM) controls the WUS gene expression in SAM and specifies FM identity. In addition, the PEBP gene TERMINAL FLOWER 1 (TFL1), an ortholog of CENTRORADIALIS (CEN) in Antirrhinum and a floral repressor, maintains indeterminate SAM growth in the inflorescence apex. TFL1 also targets the floral meristem identity gene LEAFY (LFY), a homolog of FLORICAULA (FLO) in Antirrhinum. While the developmental transition from the vegetative phase to the phase of sexual reproduction has been extensively studied, the dynamic of gene regulatory network (GRN) underlying floral reversion remains unclear. Titanotrichum oldhamii (Gesnariaceae) provides a unique opportunity to study floral reversion. In T. oldhamii inflorescenes, a FM can develop into either a flower or a cluster of ~50-70 bulbils for asexual reproduction, depending on environmental cues. To decipher the GRN dynamic between FM and bulbiliferous meristem (BM), we isolated and characterized a STM gene (ToSTM), a LFY/FLO gene (ToFLO), a TFL1/CEN gene (ToCEN), two WUS genes (ToWUS1 and ToWUS2), and three AG genes (ToAG1, ToAG2, and ToAG3). qRT-PCR revealed the upregulation of ToWUS2, ToAG2, ToSTM, and ToCEN, as well as the downregulation of ToWUS1, ToAG1, ToAG3, and ToFLO during the transition from flowering inflorescence to bulbiliferous shoot. Whole-mount RNA in-situ hybridization confirmed the positions where ToWUS2 and ToAG2 were expressed in BM. Selection analysis indicated significant purifying selection on the WUS and the AG genes. These results unravel the GRN diversification underlying floral reversion that balances sexual and asexual reproductions for successful adaptation to variable habitats.

1 - National Taiwan University, Department of Life Science, 1 Section 4 Roosevelt Road, Taipei, 10617, Republic of China
2 - Taiwan Agricultural Research Institute, Council of Agriculture, Agricultural Chemistry Division, 189 Zhongzheng Road, Wufeng District, Taichung City, Taiwan, 413008, Republic of China
3 - National Taiwan Normal University, Department Of Life Science, 88 Ting-Chow Rd., Sec. 4, Taipei, 116, Taiwan

Floral reversion
Gene regulatory network.

Presentation Type: Oral Paper
Number: DS4006
Abstract ID:993
Candidate for Awards:None

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