Most model organisms have very specific gene nomenclature guidelines, which can get confusing as they’re not always consistent with each other and have exceptions, but usually the reason is that that’s just how the field evolved. Many journals don’t strictly enforce correct nomenclature, but it is generally considered to be good practice to maintain consistency within a field. There are several resources to check the correct nomenclature for genes, proteins, RNAs, alleles, mutants, genotypes, phenotypes, etc. I’ll summarize the gene/protein symbol formatting for some of the more commonly used model species here:

• Humans: https://www.genenames.org/about/guidelines/
  • Gene: XXX, protein: XXX
• Mice: https://www.informatics.jax.org/mgihome/nomen/
  • Gene: Xxx, protein: XXX or Xxx
• Zebrafish: https://zfin.atlassian.net/wiki/spaces/general/pages/1818394635/ZFIN+Zebrafish+Nomenclature+Conventions
  • Gene: xxx, protein: Xxx
• Drosophila: https://wiki.flybase.org/wiki/FlyBase:Nomenclature
  • Fly gene formatting is complicated as it depends on whether they are dominant or recessive. I usually defer to the symbols listed on FlyBase.
• C. elegans: http://www.wormbook.org/chapters/www_nomenclature/caenornomenclature.html
  • Gene: xxx-?, protein: XXX-?, where ? is usually a number
• Arabidopsis: https://www.arabidopsis.org/portals/nomenclature/guidelines.jsp
  • Gene: XXX, protein: XXX