J Integr Plant Biol ›› 2018, Vol. 60 ›› Issue (1): 65-78.DOI: 10.1111/jipb.12596

• Plant Reproduction Biology • Previous Articles    

AGO18b negatively regulates determinacy of spikelet meristems on the tassel central spike in maize

Wei Sun1, Xiaoli Xiang2, Lihong Zhai3, Dan Zhang1, Zheng Cao1, Lei Liu1 and Zuxin Zhang1*   

  1. 1National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China
    2Institute of Biotechnology and Nuclear Technology, Sichuan Academy of Agricultural Sciences, Chengdu 610061, China
    3Medical College of Hubei University of Arts and Science, Xiangyang 441053, China
  • Received:2017-07-31 Accepted:2017-08-31 Published:2017-09-06
  • About author:*Correspondences: E-mail: Zuxin Zhang (zuxinzhang@mail.hzau.edu.cn)

Abstract:

The maize tassel represents an indeterminate male inflorescence. The number of primordia that a given inflorescence meristem produces is related to its determinacy, i.e., capacity for continued meristem activity. Transcription factors (TFs) controlling determinacy in tassel axillary meristems are well studied in maize, and small RNAs are known to influence tassel development by repressing targets, including tassel-related TFs. As core components of the RNA-inducible silence complex (RISC), Argonaute (AGO) proteins are required for small RNA-mediated repression. Here, we characterized the biological function of AGO18b, a tassel-enriched AGO. The abundance of AGO18b transcripts gradually increased during tassel development from inception to gametogenesis and were enriched in the inflorescence meristem and axillary meristems of the tassel. Repressing AGO18b expression resulted in more spikelets, which contributed to a longer central spike of the tassel. Additionally, the transcripts of several HD-ZIP III TFs that were canonical targets of microRNA166 (miR166) accumulated in the AGO18b-repressed lines. We propose that AGO18b is a negative regulator of the determinacy of inflorescence and axillary meristems, and that it acts by interacting with the miR166-HD-ZIP III TF regulatory pathway.

This study demonstrated that maize Argonaute (AGO) protein AGO18b is specifically enriched in the inflorescence meristem and axillary meristems of the tassel, and functions as a negative regulator of spikelet number on the tassel central spike by interacting with the microRNA166-mediated regulatory pathway.
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