How to automatically change status of parent issue if sub tasks status is changed?

[Markus]

Lets say that we have a user story with a couple of sub tasks. What we want is that if a sub task changes its status from "Ready" to "In Progress" that the parent issue also changes its status from "Ready" to "In Progress". 

Is that possible?

Best case would be if we could do it without any plugins. Thanks in advance!

[Alexey Matveev]

You would need a plugin like Power Scripts, ScriptRunner, Automation For Jira, Worflow Toolbox.