Here is an example of volcano plot produced using edgeR results on DEG analysis. So my question is why there is no values in the middle of plot (indicated by red circle)?

![Volcano plot][1]


  [1]: https://i.pinimg.com/originals/07/69/3d/07693dfcb3c8fe55fcae39d7caa64239.jpg
This is because there is a relationship between p-value and fold change. With no fold change (log2FC = 0) you have no significant difference hence p-value of 1 which is zero after -10log. With higher FC you can get lower p-values (hence higher -log10 values).