Abstract
The cereal endosperm is a major factor determining seed size and shape. However, the molecular mechanisms of endosperm development are not fully understood. Long noncoding RNAs (lncRNAs) function in various biological processes. Here we show a lncRNA, MISSEN, that plays an essential role in early endosperm development in rice (Oryza sativa). MISSEN is a parent-of-origin lncRNA expressed in endosperm, and negatively regulates endosperm development, leading to a prominent dent and bulge in the seed. Mechanistically, MISSEN functions through hijacking a helicase family protein (HeFP) to regulate tubulin function during endosperm nucleus division and endosperm cellularization, resulting in abnormal cytoskeletal polymerization. Finally, we revealed that the expression of MISSEN is inhibited by histone H3 lysine 27 trimethylation (H3K27me3) modification after pollination. Therefore, MISSEN is the first lncRNA identified as a regulator in endosperm development, highlighting the potential applications in rice breeding.
Highlights
The cereal endosperm is a major factor determining seed size and shape
Endosperm development begins with an initial syncytial phase followed by a cellularization phase[1,2]
We named the XLOC_057324 Long noncoding RNAs (lncRNAs) MISSEN (MIS-SHAPEN ENDOSPERM). These findings suggested that the MISSEN lncRNA might participate in seed development
Summary
The cereal endosperm is a major factor determining seed size and shape. the molecular mechanisms of endosperm development are not fully understood. We show a lncRNA, MISSEN, that plays an essential role in early endosperm development in rice (Oryza sativa). The endosperm nuclei undergo multiple rounds of mitosis without cytokinesis, producing a multinucleate cell[3]. Molecular genetic studies on early endosperm development have mainly been performed in Arabidopsis thaliana and have led to a variety of interesting findings, including the involvement of genomic imprinting and epigenetic mechanisms[7,8,9], auxin signaling[10,11], microtubule[12], and the identification of transcription factors[13] that negatively control cellularization. Hara et al 14 revealed that the rice SNF2 family helicase ENDOSPERMLESS 1 (ENL1) regulates syncytial endosperm development, suggesting that helicase family protein (HeFP) is essential for endosperm cellularization. The lncRNAs LONG-DAY-SPECIFIC MALE-FERTILITY-ASSOCIATED RNA (LDMAR)[22] and PHOTOPERIOD-SENSITIVE GENIC MALE STERILITY 1 (PMS1T)[23] are required for normal pollen development under long-day conditions and LEUCINE-RICH REPEAT RECEPTOR
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