Abstract
Although AGAMOUS-LIKE6 (AGL6) MADS-box genes are ancient with wide distributions in gymnosperms and angiosperms, their functions remain poorly understood. Here, we show the biological role of the AGL6-like gene, OsMADS6, in specifying floral organ and meristem identities in rice (Oryza sativa L.). OsMADS6 was strongly expressed in the floral meristem at early stages. Subsequently, OsMADS6 transcripts were mainly detectable in paleas, lodicules, carpels and the integument of ovule, as well as in the receptacle. Compared to wild type plants, osmads6 mutants displayed altered palea identity, extra glume-like or mosaic organs, abnormal carpel development and loss of floral meristem determinacy. Strikingly, mutation of a SEPALLATA (SEP)-like gene, OsMADS1 (LHS1), enhanced the defect of osmads6 flowers, and no inner floral organs or glume-like structures were observed in whorls 2 and 3 of osmads1-z osmads6-1 flowers. Furthermore, the osmads1-z osmads6-1 double mutants developed severely indeterminate floral meristems. Our finding, therefore, suggests that the ancient OsMADS6 gene is able to specify “floral state” by determining floral organ and meristem identities in monocot crop rice together with OsMADS1.
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Acknowledgements
We gratefully acknowledge B Han from National Center for Gene Research, Chinese Academy of Sciences (CAS) and Rice Genome Resource Center (RGRC) for providing BAC clone, cDNA clone and Tos17 insertion line. We thank Z-J Luo and M-J Chen from Shanghai Jiao Tong University for mutant screening and generation of F2 populations, X-Y Gao from Institute of Plant Physiology and Ecology, SIBS, CAS, for SEM, H Yu from National University Of Singapore for critical reading of this manuscript and H Ma from Fudan University for helpful discussion. This work was supported by funds from the National Basic Research Program of China (2009CB941500, 2006CB101700), the National Natural Science Foundation of China (30725022, 30830014 and 90717109) and the Shanghai Leading Academic Discipline Project (B205).
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Supplementary information, Figure S1
Flower phenotypes of osmads6-2 and osmads6-1/osmads6-2 at stage Sp8. (PDF 404 kb)
Supplementary information, Figure S2
Analyses of OsMADS6 RNAi plants. (PDF 85 kb)
Supplementary information, Figure S3
Alignment of the amino acid sequences of AGL6-like genes. (PDF 1270 kb)
Supplementary information, Figure S4
Phylogenetic tree of 38 SEP, 34 AP1 and 33 AGL6 genes, 7 TM3-like, 4 AG-like and 4 CRM6 genes as out groups. (PDF 158 kb)
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Li, H., Liang, W., Jia, R. et al. The AGL6-like gene OsMADS6 regulates floral organ and meristem identities in rice. Cell Res 20, 299–313 (2010). https://doi.org/10.1038/cr.2009.143
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DOI: https://doi.org/10.1038/cr.2009.143
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