May 7 (Reuters) - Wall Street’s main indexes opened higher on Friday, powered by a rally in mega-cap stocks after a downbeat jobs report eased valuation concerns. The Dow Jones Industrial Average rose 29.74 points, or 0.09%, at the open to 34,578.27. The S&P 500 opened higher by 8.72 points, or 0.21%, at 4,210.34, while the Nasdaq Composite gained 90.25 points, or 0.66%, to 13,723.09 at the opening bell. (Reporting by Shreyashi Sanyal in Bengaluru; Editing by Maju Samuel) Our Standards: The Thomson Reuters Trust Principles.