The rice Os02g0682200 has been reported as MADS6 or MFO1 more than four times since the year 2009. As a member of MADS-box gene family, MADS6 draws attention of plant molecular biologists for its special functions in the regulation of rice flowers development.
OsMADS6, the AGL6-like gene in rice, plays an essential role in specifying floral organ, meristem identities and endosperm nutrient accumulation in rice. It is also an important epigenetic regulator in rice. The study by Shinnosuke Ohmori et al. in 2009 showed that the loss of OsMADS6 function in rice resulted in aberrant floral morphology. The study by Dabing Zhanga et al. in 2011 further explained how OsMADS6 worked with OsMADS3, OsMADS16, OsMADS13 and OsMADS58 et al. and showed that OsMADS6 is a key player in specifying flower development via interacting with other floral homeotic genes in rice.
Wild Type VS. Mutant
- In the research reported by Dabing Zhang et al. in 2010, a osmads6 mutant line with flower morphological defects was isolated from Japonica subspecies 9522 background treated with 60-Co γ-ray (280 Gy). No significant differences were observed when compared with the vegetative development stages, flowering time or inflorescene morphology of Wild-Type and the osmads6 mutant (Figure 1A and 1B).
- However, when compared with the morphology of flower organs, a defection of floral development could be found in osmads6 mutant. The spikelets of osmads6-1 at stage In9 showed somewhat larger palea than Wild-Type (Figure 1C and 1D). The wellinterlocked lemma/palea structure was destroyed in the osmads6-1 mutant flower because of the altered marginal tissue (Figure 1F). Ectopic indeterminate glume-like structures enclosed the stamen filament in osmads6-1 mutant flowers (Figure 1G).
- In the research reproted by Shinnosuke Ohmori et al. in 2009, another MADS6 mutant mfo1-1 was described. There is also no obvious abnormalities between mfo1-1 and Wild-Type in the vegetative stage, however, abnormal flower morphological was observed in mfo1-1. A slightly enlarged palea and were half open was found in the florets of mfo1-1 (Figure 2A and 2B).
- Compared with Wild-Type, Mfo1-1 is in defect of interlocking between the lemma and palea (Figure 2C and 2D). The mfo1-1 palea also lacked the membranous marginal region of palea which is found in Wild-Type and its surface is relatively rougher than that of the Wild-Type lemma (Figures 2E and 2F).
- The microarray studies by Jian Zhang et al. showed that OsMADS6 was highly expressed in the endosperm, compared with other vegetative tissues. Their further RT-PCR and RNA in-situ hybridization analyses showed that OsMADS6 was expressed in flower and developing seeds, but was not detectable in root, leaf and suspension cells (Figure 3).
- The gene expression analysis by Dabing Zhang et al. in 2010 showed that OsMADS6 was strongly expressed in the floral meristem at early stages. Its transcripts could also be detected in paleas, lodicules, carpels and the integument of ovule. In conclusion, OsMADS6 expression was associated with the specification of floral organ as well as meristem identity.
- The phylogenetic analyses made by Dabing Zhang et al. OsMADS6 belonged to an ancient and conserved AGL6 family. Both gymnosperms and angiosperms shared one common ancestor of AGL6-like genes. And the AGL6-like genes from grasses form two paralogous clades: the OsMADS17-clade contains OsMADS17 gene with an ortholog from Sorghum and the other genes, namely, OsMADS6-clades .
Labs working on this gene
- Rice Biotechnology Research Subteam (Hokuriku Region), National Agricultural Research Center, National Agriculture and Food Research Organization, Niigata 943-0193, Japan;
- Division of Genome and Biodiversity Research, National Institute of Agrobiological Sciences, Ibaraki 305-8602, Japan;
- School of Life Science and Biotechnology, Shanghai Jiaotong University, Shanghai 200240, China;
- Department of Biochemistry and Molecular Biology, Mississippi State University, MS 39762, USA;
- Institute of Plant Science, State Key Laboratory of Hybrid Rice, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China;
- Dipartimento di Scienze Biomolecolari e Biotecnologie, Universita` degli Studi di Milano, 20133 Milan, Italy;
- Bio-X Center, Key Laboratory of Genetics and Development and Neuropsychiatric Diseases, Ministry of Education, Shanghai Jiao Tong University, Shanghai 200240, China;
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore-560012, India;
- Department of Plant Biotechnology, School of Biotechnology, Madurai Kamaraj University, Madurai-625 021, Tamil Nadu, India;
- Institute of Biotechnology, Viikinkaari 1, FI-00790, University of Helsinki, Finland
- Ohmori S, Kimizu M, Sugita M, et al. MOSAIC FLORAL ORGANS1, an AGL6-like MADS box gene, regulates floral organ identity and meristem fate in rice[J]. The Plant Cell Online, 2009, 21(10): 3008-3025.
- Li H, Liang W, Jia R, et al. The AGL6-like gene OsMADS6 regulates floral organ and meristem identities in rice[J]. Cell research, 2009, 20(3): 299-313.
- Zhang J, Nallamilli B R, Mujahid H, et al. OsMADS6 plays an essential role in endosperm nutrient accumulation and is subject to epigenetic regulation in rice (Oryza sativa)[J]. The Plant Journal, 2010, 64(4): 604-617.
- Li H, Liang W, Hu Y, et al. Rice MADS6 interacts with the floral homeotic genes SUPERWOMAN1, MADS3, MADS58, MADS13, and DROOPING LEAF in specifying floral organ identities and meristem fate[J]. The Plant Cell Online, 2011, 23(7): 2536-2552.
- Yadav S R, Khanday I, Majhi B B, et al. Auxin-responsive OsMGH3, a common downstream target of OsMADS1 and OsMADS6, controls rice floret fertility[J]. Plant and Cell Physiology, 2011, 52(12): 2123-2135.