Two transcription factors, MYB64 and MYB119, and their target cis-regulatory element control egg cell-specific gene expression in Arabidopsis.

With the growing emphasis on cell-type-specific gene expression during development, genes that exhibit restricted expression patterns have emerged as key regulators of plant reproductive processes. Notably, the egg cell-specific genes ECS1 (EGG CELL-SPECIFIC1) and EC1 (EGG CELL1) have been functionally characterized and shown to be essential for successful fertilization. However, the mechanisms that restrict these genes to specific cell types remain largely unknown. In this study, we identified a cis-regulatory element, designated ESM (Egg cell-Specific Motif), that directs egg cell-specific expression of ECS1 in Arabidopsis thaliana. Two transcription factors, MYB64 and MYB119, were identified as factors that bind to the ESM element. Loss of MYB64 and MYB119 function resulted in expression of pECS1::ECS1-GFP in both egg and synergid cells, leading to reduced LURE1.2 expression in synergid cells and defective pollen tube attraction. Furthermore, the MYB64/119-ESM module was found to regulate multiple egg-cell-specific genes. Adding the ESM element to the promoters of ES1 and ES2, two genes expressed in the female gametophyte, restricted their expression to egg cells. Overall, our findings reveal that the MYB64/119-ESM module contributes to the regulation of egg cell-specific gene expression.