A good solution for this is to use the Behave plugin for JIRA.
In a good SCRUM team, your domain experts and business owners should define the backlog and describe what they want. It is awesome that you can then immediately add the Given/When/Then definitions for test scenario's.
JBehave also supports getting the .feature files from Google Docs. There is no syntax highlighting plugin for google docs though, so this only takes care of the synchronization problem.
