The debate over stem cell research soon could be coming to your local grocery store parking lots, shopping centers and city sidewalks.

The secretary of state's office said Tuesday that it has given the go-ahead for supporters of a proposed constitutional amendment protecting stem cell research and treatments to begin gathering petition signatures from voters.

They have until May 9 to collect about 145,000 valid signatures, an amount that can vary depending on the areas they target. The proposal is intended for the November 2006 ballot.

The petition drive is a reaction to unsuccessful legislative efforts by some anti-abortion activists to ban a kind of early stem cell research known informally as therapeutic cloning and technically as somatic cell nuclear transfer.

In that procedure, scientists replace the nucleus of an unfertilized egg with the nucleus of a cell from the patient's body, such as a skin or nerve cell. The altered egg then is stimulated to grow, and the resulting stem cells are harvested.

Stem cells can potentially develop into any type of human tissue. Researchers hope those cells can lead to cures for ailments such as diabetes, Parkinson's disease, cancer and spinal cord injuries.

But opponents, including Missouri Right to Life and the Missouri Catholic Conference, contend the procedure destroys human life.

Republican Gov. Matt Blunt already has lent his support to the ballot initiative. It is sponsored by the Coalition for Lifesaving Cures, a group that includes medical researchers and patient advocacy organizations.

To qualify for the ballot, initiatives must receive petition signatures equal to 8 percent of the votes cast in the 2004 governor's election in each of six of the state's nine congressional districts.