Non-engineered tomatoes produce high levels of an enzyme called pectin methylesterases, which creates free carboxylic acids in fruit cell walls. These acids bind calcium and immobilize it in the fruit, Handa said.
"If you have a lot of pectin methylesterase activity, much of the calcium in the cells becomes bound to the cell wall," Mitcham said. "That calcium is then unavailable to protect the cell membrane and prevent these physiological disorders."
Handa's strategy for producing thicker juices involved silencing pectin methylesterase production in a transgenic tomato, greatly reducing the binding sites for calcium within the fruit cell walls. That allowed the calcium to be used in other parts of the tomato's cells.
"Freed-up calcium from cell walls likely overcomes the underlying cause of blossom end rot," Handa said.
Mitcham will continue to study the mechanisms that cause blossom end rot in tomatoes, as well as how pectin methylesterases and calcium may play roles in other plant diseases thought to be caused by calcium deficiencies, including in apples, lettuce, peppers and watermelons.
Handa said this development, and the fact transgenic plants have become more common, might get tomato producers interested in the tomato genotype he developed more than 20 years ago.
"We're coming to a time when people are starting to use genetically modified crops," Handa said. "The technology is matured and dependable and ready to be used now."
|Contact: Brian Wallheimer|