Maize Transcription Factor ZmEREB93 Negatively Regulates Kernel Development

Maize, a kind of crucial crop, is widely used in food supply, livestock feed, and industry. AP2/EREBP (APETALA2/ethylene response element-binding protein) transcription factor (TF) plays an important role in plant growth, development, and stress response. Previous study showed that ZmEREB93 might regulate seed size as a target gene of ZmBES1/BZR1-5 TF. ZmEREB93 was cloned and used to analyze its expression pattern and function, which lays foundation to clarify the function and mechanism of ZmEREB93 regulating seed size.

The full length of ZmEREB93 was cloned from maize inbred line B73 by PCR. The characters of nucleotide and amino acid sequences were analyzed by informatic methods. Subsequently, the tissue expression specificity of ZmEREB93 was analyzed via quantitative real time PCR (qRT-PCR). The expression vector in plant and yeast was constructed and used for subcellular localization and transcription activation assay, respectively. ZmEREB93 was transformed into Arabidopsis mediated by agrobacterium transformation. The seed phenotype of transgenic lines was analyzed. Finally, the potential target genes of ZmEREB93 were screened by chromatin immunoprecipitation sequencing (Chip-seq) and co-expression analysis, and further confirmed by yeast one hybrid (Y1H).

The ZmEREB93 gene was cloned by PCR. Sequence analysis showed that ZmEREB93 had no intron and a 618 bp ORF, encoding 205 amino acids with a highly conserved AP2 domain and belongs to the ERF subclade of AP2 family. The results of qRT-PCR showed that the ZmEREB93 gene highly expressed in kernels of 15 and 25 days after pollination (DAP), and slightly expressed in stem and root, but did not express in tassel, silk and bract. The expression level of ZmEREB93 was the highest in 25 DAP kernels reached 11 times of that in 15 DAP kernels. The results of transcriptional activation and subcellular localization assay exhibited that ZmEREB93 protein had no transcriptional activation activity in yeast cells and was localized in the nucleus, respectively. Compared to wild type, the seeds of transgenic lines were significantly smaller and showed lower thousand-seed-weight. Chip-seq and co-expression analysis suggested that the Zm00001d013611, Zm00001d006016, Zm00001d027448 and Zm00001d03991 genes were candidate target genes regulated by ZmEREB93 TF. The result of Y1H showed that ZmEREB93 directly bind to Zm00001d013611 promoter.

Maize ZmEREB93 TF specifically expressed in seeds and negatively regulated seed size.