Characterization of Osmads6-5, a null allele, reveals that OsMADS6 is a critical regulator for early flower development in rice (Oryza sativa L.)
AGL6-clade genes are a subfamily of MADS-box genes and preferentially expressed in floral organs. OsMADS6 and OsMADS17 are two AGL6-like genes in rice. OsMADS17 has been shown to play a minor role in floral development and appears to result from a duplication of OsMADS6. OsMADS6 was initially named as MFO1 for mosaic floral organs based on its moderate mutant phenotypes. So far, four moderate or weak mutant alleles of OsMADS6 have been described, providing valuable insights into its role in flower development. Here, we report a null allele of OsMADS6 (Osmads6-5), which exhibited a strong mutant phenotype in spikelet without affecting vegetative traits, causing all floral organs except lemma homeotically transformed into lemma-like organs (LLOs) as well as an indeterminate floral meristem, thus resulting in a mutant floret consisting of reiterating whorls of lemma and LLOs. In consistently, over-expression of OsMADS6 led to additional lodicule-, stamen- and carpel-like organs. Expression analysis showed that OsMADS6 controls the formation of the incipient primordia of lodicule, stamen and carpel via regulating the expression of class B, C and SEP-like MADS-box genes. Taken together, our results revealed that OsMADS6 acts as a critical regulator for early flower development in rice and provide novel insights into the molecular mechanism of OsMADS6.
KeywordsRice Osmads6-5 Null allele Floral meristem determinacy Floral organ identity
Mosaic floral organ
Suppressor of overexpression of CO 1
Floral binding protein2
Scanning electron microscopy
Reverse transcription polymerase chain reaction
Real-time quantitative RT-PCR
Simple sequence repeat
Green fluorescent protein
We thank Yuanchang Zhou, Zhiwei Chen, Runsen Pan, Lihui Lin, Huazhong Guan, Xuzhang Zhang, Lijun Zhuang and Leilei Zheng of Fujian Agricultural & Forestry University and Yansheng Zhang, Yu’e Zhang, Qun Li and Xingming Hu of the Institute of Genetics and Developmental Biology of Chinese Academy of Sciences for their helps in the experiment, and Kang Chong of the Institute of Botany of Chinese Academy of Sciences for supplying the RNAi vector pTCK303. This work was supported by the National High Technology Research and Development Program of China (2006AA10Z128), the National Basic Research Program (2011CB100202), the Natural Science Foundation of China (30671122) and Natural Science Foundation of Fujian Provincial of China (B0620001).
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