Apples grow larger when cells don’t divide

July 1st, 2010 - 9:43 pm ICT by IANS  

Washington, July 1 (IANS) Fast-food restaurants can supersize French fries and drinks, but nature has found a way to super-size a type of apple by not letting its cells divide.
Peter Hirst, Purdue University associate professor of horticulture, found that an anomaly in some Gala apple trees causes some apples to grow much larger than others because cells aren’t splitting. A Gala is a clonally-propagated apple with a mild and sweet flavour.

The findings showed that the new variety, called Grand Gala, is about 38 percent heavier and has a diameter 15 percent larger than regular Galas.

“It’s never been found in apples before,” Hirst said. “This is an oddball phenomenon in the apple world.”

Hirst is trying to understand what causes the difference in the size of apples - for instance, why Gala apples are so much larger than crab-apples.

“There is real incentive for fruit growers to increase the size of their apples,” Hirst said. “At 125 apples per bushel, a grower gets 8 cents per apple. But if they have larger apples - 88 per bushel - the price more than doubles.”

Since different apple varieties don’t always have the same genes controlling the same functions, comparing Galas to crab-apples isn’t an easy way to understand the mechanisms that control their destined sizes. But the Grand Gala seemed to provide an opportunity to unravel the mystery.

“The way the Grand Gala was found was that someone in an orchard full of Gala trees noticed that one branch had different-sized apples than the rest of the tree. They grafted new trees from this branch,” Hirst said. “These are just chance events.”

Larger apples tend to have more cells than their smaller counterparts, so Hirst theorised that there was a gene or genes that kept cell division turned on in Grand Gala.

Instead, he found that Grand Gala had about the same number of cells as a regular Gala, but those cells were larger.

Normally, cells make a copy of their DNA, grow and then split. Each of those cells continues the process. Through a phenomenon called endoreduplication, the cells in Grand Gala make copies of their DNA, but don’t divide. Instead, the cells grow, add more copies of the DNA and continue that growth.

The Grand Gala fruit has the same core size, so the added size and weight is in the meat, or cortex, of the fruit. Hirst said they’re also crunchier and tend to taste better, said a Purdue University release.

Hirst’s study found that one or more of a handful of genes is likely responsible for the endoreduplication. And while it may be possible to isolate those genes and find ways to increase the size of other apples, Hirst said it’s unlikely.

These findings were reported in the current issue of the Journal of Experimental Botany.

Related Stories

Tags: , , , , , , , , , , , , , , , , , , ,

Posted in Sci-Tech |

Subscribe