Robin Roberts departed " Good Morning America" this morning for an extended medical leave surrounded by family, "GMA" staff and a promise from her fellow anchors to "keep her seat warm" while she is gone.

"The greatest tragedy is to have the experience and miss the meaning," Roberts said. "I am determined not to miss that meaning because through it I have discovered that I have been given many gifts, gifts that will carry me through this difficult time. "

Roberts told viewers in July that she had been diagnosed with MDS, or, myelodysplastic syndrome, a rare blood disorder. She was scheduled to begin an extended medical leave in preparation for a bone marrow transplant on Friday but moved the date to Thursday in order to fly home to Mississippi to be with her ailing mother, Lucimarian, and her family in the hurricane zone.

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"Our beloved mother, the matriarch of our family, 88-years-old, has had some health issues recently and it's got to the point that Sally-Ann and I need to get home so I'm leaving a day early," Roberts said.

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Sally-Ann is Roberts' older sister, a local television news anchor in New Orleans, who will be Roberts' bone marrow donor. It was found that Sally-Ann was an excellent match for Roberts, a rarity as marrow donors are scarce and particularly for African-American women.

On the show today, Roberts and fellow anchors Josh Elliott, Sam Champion, George Stephanopoulos and Lara Spencer announced that ABC News' Diane Sawyer, Katie Couric , Barbara Walters and Elizabeth Vargas will fill in for Roberts while she is away.

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"You're the team captain and the team is going to run in your absence but you're never really going to be gone," Elliott said.

"GMA" also announced that a headline-making roster of stars will also pitch in to keep the show's momentum going, including Oprah Winfrey, Kelly Ripa, Chris Rock, Rob Lowe and the cast of ABC's "Modern Family." There will also be surprise guests during Roberts' leave.

"This means so much, that these friends are stepping up like this," Roberts said. "It doesn't surprise me at all because they love the program, and they love what we're doing and I love them for doing that."

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Country superstar Martina McBride flew in from her national tour to perform a special tribute to Roberts live in the show's Times Square studio. Her fellow anchors gifted her with presents including pajamas for her hospital stay and a bell to ring whenever she needs anything. The show's executive producer, Tom Cibrowski, presented Roberts with a book of well wishes and support from the show's staff.

"I will be back, you know," Roberts said amidst all the tributes. "This is just see you later. See you soon. I will get back as fast as I can."

"I love you and I'll see you soon," she said.

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