Domains (SEO) question

Hi guys,
I?d like youto help me out with this one with your kind advice.
Say, I havea website called en.sitename[.]com and a website sitename[.]com
Do you think whatever SEO work that gets done on en.sitename[.]com "spreads over" tositename.com or does Google sees sitename[.]com as a separate website?
Looking forward to your reply!

It's the other way around, I think: whatever work is done to your root domain will get spread to subdomains, but it doesn't work as much the other way around.

Build your root page (sitename.com) and your subdomains will be strengthened too.

Thanks guys. we've just been trying to pursue different (experimental) SEO strategies for ru.domain[.]com and domain[.]com and are afraid that the SEO strategy for ru.domain might bring down the main domain[.]com (the aim is to get ru.domain up in its Yandex.ru as opposed to domain[.]com in its Google.com)