The film is an adaptation of the book "A Long Way Home" written by Indian born Australian businessman Saroo Brierley. The book talks about his separation from his mother and how he was adopted by an Australian family.
"The film is based on a real life incident. Its about a lost boy who gets adopted by an Australian pair. Its his journey from Kolkata to Tasmania," Tannishtha told IANS.
Directed by Garth Davis, the film will be produced by Australia's See-Saw Films.
Although, Tannishtha didn't reveal much about her role, she said it will definitely be a crucial one and will be a surprise for all.
"My role in the film is pretty crucial. Its a surprise in the story. Its going to be a very changing thing in the plot," said Tannishtha, whose film "Jal" has found a place in the Oscar long list of 2014 in two categories - Best Picture and Best Original Score.
Sharing the details about the shooting schedule, Tannishtha said "the shooting of 'Lion' will start Jan 17 in Kolkata. It is expected to hit the theatres at the end of this year."
The film also stars Hollywood actors Nicole Kidman and Dev Patel.
After Kolkata the shooting will reportedly move to Australia.
Tannishtha has previously appeared in international films including "Schatten der Zeit" (Shadows of Time), "Brick Lane" and "Anna Karenina".
