Under the state’s new health care cost-control law, legislators are counting on physician assistants like Tuff as critical partners in the effort to curb medical spending, improve the coordination of treatment, and give patients easier access to basic care amid a shortage of primary care doctors.

A little-known provision of the law, which Governor Deval Patrick signed in August, expands the role of physician assistants by requiring health plans to list them as primary care providers in directories and allow patients to choose a physician assistant as their provider. They still will work on teams with doctors, but they will have their own group of patients for whom they are primarily responsible. Nurse practitioners were given similar status in a 2008 state law.

Even before Patrick approved the cost-control law, demand for physician assistants had been intensifying, in part because of the 2006 Massachusetts law requiring all state residents to have health insurance. That put more people in search of physical exams, screening tests and other basic primary care for which they are now covered. The federal Affordable Care Act, which extends the requirement for insurance coverage to most Americans, is expected to have a similar impact nationally.

Tufts University School of Medicine has started a new master’s degree program for physician assistants, and plans to admit its first class of 30 students in January. Boston University School of Medicine is launching a physician assistant training program next spring. And the number of yearly applicants to Northeastern University, where Tuff is earning her degree, has doubled to 600 for 40 spots over the past five years.

The US Labor Department has tagged the profession as one of the fastest growing, in part because training programs are far less expensive than medical school — about $100,000 — and graduates earn $90,000 or more right away

“Now that we have the [people] covered . . . we have to provide the care,’’ said Terry Fulmer, dean of Northeastern’s Bouvé College of Health Sciences. “That creates a tremendous work force demand. Nurse practitioners and physician assistants can fill that void.’’

The recently enacted health care cost-control law also allows nurse practitioners to sign forms that up until now have required a doctor’s signature, such as permission for a student to participate in school sports or for a sick employee to stay home from work.

Doctors, nurse practitioner and physician assistants all are qualified to perform exams, diagnose and treat disease, order and interpret diagnostic tests and prescribe medications, but they complete training programs that vary in length and can emphasize different skills. Physicians are generally more qualified to manage very complex or unstable patients such as those with advanced cancer or kidney disease.

Work done by physician assistants varies based on experience and the comfort level of the doctors in charge of the practice. Tuff, who worked as an emergency medical technician before enrolling at Northeastern, this month began a year of clinical rotations at Harvard Vanguard Medical Associates in Cambridge to learn primary care. Next, she will train in surgery at Carney Hospital in Boston; many physician assistants who work in surgery make incisions and stitch-up patients and help manage their hospital care.

Patients will be able to choose a physician assistant as their primary care provider through their insurer, or doctor’s office. In some cases, patients may be able to get an appointment with a physician assistant more quickly, especially if they are looking for specific qualities such as a female provider.

Doctors traditionally are trained to take charge and make decisions alone, so some are not comfortable with a team approach. That is one reason medical schools are starting physician assistant training programs, to prepare doctors early on to work with physician assistants, said Dr. Harris Berman, dean of Tufts medical school.

“We have to reorganize the way we provide care,’’ he said. “One doctor can extend what they’re doing to many more patients’’ by hiring a physician assistant.