摘要
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 RNAmediated repression. Here, we characterized the biological function of AGO8b, a tassel-enriched AGO. The abundance of AGO8b transcripts gradually increased during tassel development from inception to gametogenesis and were enriched in the inflorescence meristem and axillary meristems of the tassel. Repressing AGO8b 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 micro RNA66(miR66) accumulated in the AGO8b repressed lines. We propose that AGO8b is a negative regulator of the determinacy of inflorescence and axillary meristems, and that it acts by interacting with the miR66-HD-ZIP Ⅲ TF regulatory pathway.
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 RNAmediated repression. Here, we characterized the biological function of AGO_18b, a tassel-enriched AGO. The abundance of AGO_18b transcripts gradually increased during tassel development from inception to gametogenesis and were enriched in the inflorescence meristem and axillary meristems of the tassel. Repressing AGO_18b 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 micro RNA_166(miR_166) accumulated in the AGO_18b repressed lines. We propose that AGO_18b is a negative regulator of the determinacy of inflorescence and axillary meristems, and that it acts by interacting with the miR_166-HD-ZIP Ⅲ TF regulatory pathway.
基金
supported by the National Natural Science Foundation of China (91635303, 31501320) (www.nsfc.gov.cn)
National Basic Research Program of China (2014CB138203) (www.most.gov.cn)
