I don't understand what you actually want to inquire. It could be possible that you have not a good understanding of the topic itself. Please go through simplified definition and try to see the contrast and connection.

However, gene-environmental interaction is an effect while gene expression is a resultant of that or any other interaction. As an author for your article, it is you who will decide if those can be described and discussed in your article and would that make sense.

I presume if you encountered it in a tutorial or book, the example could be dependency of gene expression on the factors gene and environment where significance of an interaction is determined by anova. If that is not the case then, gene X environment would simply determine your phenotypic output while a gene expression measure would suggest changes in the transcription of those genes when you see that particular phenotype. Thus, the former is a subject of genetics while the latter becomes a subject of functional genomics.

- Generally, you adress the issue of gene x environment interaction to know whether the association of a genotype with a phenotype depends on the environment. To this aim, you write the formula: phenotype = A + (B x genotype) + (C x environment) + D (genotype x environment).

- You may also investigate the effect of environment on gene expression. To this aim, you can compare a group of samples exposed to condition A with a group of samples exposed to condition B. To this aim, you perform transcriptome study with microarrays or the RNA-seq method.