World No 2 Kim Clijsters has withdrawn from Wimbledon with a foot injury.
The absence of the current US and Australian champion means that last year's runner-up Vera Zvonareva from Russia becomes the second seed.
The popular Clijsters, who won the 2009 US Open just three tournaments into a comeback from a two-year retirement in which she gave birth to a daughter, has had her season disrupted by injury since beating China's Li Na to win the Australian Open.
Serena Williams, the reigning Wimbledon champion, who has just returned from an 11-month absence because of injury and health problems, rises to number seven seed.
The seeding committee had earlier bumped up the American from her world ranking of 26 to take into account her formidable record at the All England Club.
With Clijsters out, Williams' chances of a stunning comeback to claim a fifth Wimbledon singles title will be enhanced -- as will the prospects of sister Venus, who is 23rd seed, after her return from a five-month injury break in Eastbourne this week.
In the men's competition, Andy Murray has been handed the fourth seeding after the All England Club elected to adhere to the top-five world rankings.
Defending champion Rafael Nadal is the top seed ahead of Novak Djokovic, with six-time winner Roger Federer third on the list.