The OsIME4 gene identified as a key to meiosis initiation by RNA in situ hybridization

Authors: ZHOU, WENQI - Gansu Academy Of Agricultural Sciences; LI, ZICHAO - China Agricultural University; ZHANG, JIANPING - Gansu Academy Of Agricultural Sciences; Mou, Beiquan; ZHOU, WEI - Former ARS Employee

Submitted to: Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2021
Publication Date: 4/21/2021
Citation: Zhou, W., Li, Z., Zhang, J., Mou, B., Zhou, W. 2021. The OsIME4 gene identified as a key to meiosis initiation by RNA in situ hybridization. Plant Biology. 23(5):861-873. https://doi.org/10.1111/plb.13274.
DOI: https://doi.org/10.1111/plb.13274

Interpretive Summary: The formation of asexual seeds in plants holds great promise as a breeding system for hybrid rice production. A process to produce asexual seeds, apomixis, could be used to propagate hybrid rice. We conceived a two-step mechanism for inducing apomixis. The first step was to be the induction of secondary megaspore mother cells (MeMCs) in the ovule. The second step was to be the induction of apomixis in the secondary MeMCs without affecting the primary MeMC. Apomixis in the MeMCs can be achieved by identifying and manipulating meiosis-specific genes. To achieve apomixis in the secondary MeMCs, an understanding of meiosis initiation is the key step. We searched and investigated the expression of the rice genome and found that the OsIME4 gene expressed sense transcripts in mitotic cells and antisense transcripts in pre-meiotic cells. Our data suggest OsIME4 sense transcripts, which encodes a putative enzyme (mRNA N6-adenosine methyltransferase), keep rice cells at mitosis status, and the non-coding antisense transcripts of OsIME4 convert the cell status from mitosis to meiosis by inhibiting the expression (transcription and translation) of sense transcripts. Over expressing the sense transcripts of OsIME4 or silencing its antisense transcripts or doing both to by-pass meiosis will be a milestone in engineering apomixis in rice. Although apomixis is complicated, the increase in knowledge of the genetic and molecular control of plant reproductive development will provide better insights into the regulation of apomixis. The understanding of reproductive machinery in plants should enable the engineering of apomixis in sexual crops in the near future.

Technical Abstract: Entry into meiosis is a key developmental decision in gametogenesis, especially, in formation of asexual seeds in plants, which holds great promise as a breeding system for hybrid rice. Apomeiosis in the megaspore mother cells (MeMCs) can be achieved by identifying and manipulating meiosis-specific genes. Based on expression analysis, we identified OsIME4 sense and antisense transcript involved in rice meiosis initiation in a similar way as initiation of meiosis in budding yeast. Our data suggest OsIME4 sense transcripts, which encodes a putative mRNA N6-adenosine methyltransferase, keep rice cells at mitosis status through some kinds of epigenetics way (DNA/RNA methylation), and the non-coding antisense transcripts of OsIME4 convert the cell status from mitosis to meiosis by inhibiting the expression (transcription and translation) of sense transcripts. Our results provide novel insights into meiosis initiation in rice and engineering of apomixis in sexual crops by manipulating the OsIME4 sense and antisense transcripts.