Sept 29 (Reuters) - Memory chipmaker Micron Technology forecast first-quarter revenue below Wall Street estimates on Thursday as demand from its key end markets including PCs and smartphones worsen amid rising worries about an economic downturn.

The company forecast adjusted current-quarter revenue to be $4.25 billion, plus or minus $250 million. Analysts on average expected revenue to be $5.62 billion, according Refinitiv data. (Reporting by Chavi Mehta in Bengaluru and Jane Lanhee Lee; Editing by Krishna Chandra Eluri)