OsLEC1/OsHAP3E Participates in the Determination of Meristem Identity in Both Vegetative and Reproductive Developments of RiceF

Abstract

In the vegetative phase of plant development, the shoot apical meristem (SAM) produces leaf primordia in regular phyllotaxy, and transforms to the inflorescence meristem when the plant enters reproductive growth, which will undergo a series of identity differentiations and will finally form a complete and fertile panicle. Our previous studies indicated a tissue-specific expression pattern of the OsLEC1 (leafy cotyledon) gene, which is homologous to the Arabidopsis AtLEC1 gene and belongs to the CCAAT-binding protein HAP3 subfamily, during embryo development. Expression of additional OsLEC1 genomic sequences resulted in abnormalities in the development of leaves, panicles and spikelets. The spikelets in particular presented abnormities, including panicle and spikelet-like structures that occurred reiteratively inside prior spikelets, and the occasional spikelet structures that completely transformed into plantlets (a reproductive habit alteration from sexual to asexual called "pseudovivipary"). Analysis showed that OsLEC1 interacts with several SEPALLATA-like MADS transcription factors, suggesting that increased levels of the OsLEC1 protein might interfere with the normal interaction network of these MADS proteins and lead to defective spikelet development. The expression of OsMADS1 was dramatically reduced, and the DNA methylation level of cytosine in certain regions of the OsMADS1 promoter was increased under OsLEC1 overexpression. These results indicate that OsLEC1 affects the development of leaves, panicles and spikelets, and is a key regulator of meristem identity determination in both rice (Oryza sativa) vegetative and reproductive development.