What purpose you need it?

diagnosis? genotyping? 

For quantifying expression by relative qPCR.

Are you just doing promastigotes or comparing amastigotes to Pros? 

I am just useing promastigotes.

Our collaborator uses alpha tubulin, which I have seen in other papers. I ask because levels completely change in amastigotes so it doesn't serve as one across the forms which is what I am in need of. 

I have seen in some articles alpha tubulin is stable in promastigoes but not in amastigotes.

Catherine S Nation Do you found a housekeeping gene across the forms amastigote and promastigote? I also need it

Yes. 18S rRNA

You can find in my article:

https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0005774&rev=2

Good Luck

thank you Alireza Badirzadeh

You are welcome Maria.