October 27, 2013
Kiwifruit Became More Nutritious Following Genome Duplication Events
redOrbit Staff & Wire Reports - Your Universe Online
Scientists working to sequence the genome of the kiwifruit have revealed that the berry has recently undergone a pair of whole-genome duplication events, according to new research published earlier this month in the journal Nature Communications.
Zhangjun Fei, an associate professor at the Boyce Thompson Institute at Cornell University, and his colleagues also discovered that there were many similarities between the kiwi’s more than 39,000 genes and those of other plant species, including tomatoes and potatoes.
However, they were surprised to learn of the duplication events. When genes are duplicated, they explain, the extra genes can wind up mutating in order to perform new functions previously lacking in the organism. This process, which is known as neofunctionalization, turned out to be beneficial to the kiwi, according to Fei.
“The duplication contributed to adding additional members of gene families that are involved in regulating important kiwifruit characteristics, such as fruit vitamin C, flavonoid and carotenoid metabolism,” he said in a statement Friday. Previous research had extensively analyzed the metabolic accumulation of those substances, but this marks the first time that genome sequence data had been available.
Fei was one of several US and Chinese researchers who participated in the project, which used a Chinese variety of kiwifruit known as “Hongyang” in order to produce the draft sequence. After comparing its genome to those of grape, rice, tomato, and a type of mustard weed called Arabidopsis, they found 8,000 genes that were common among all five species, including some related to fruit growth and ripening, nutrient metabolism, and disease resistance.
“One of the most remarkable findings of the study was uncovered when scientists observed a high percentage of similarities within the kiwifruit DNA,” the university noted. “The data revealed two unusual mishaps that occurred in the process of cell division about 27 and 80 million years ago, when an extensive expansion of genes arose from an entire extra copy of the genome, followed by extensive gene loss.”
Fei, who called the kiwi “an economically and nutritionally important fruit crop,” said that the genome sequence he and his colleagues have created “will serve as a valuable resource for kiwifruit research and may facilitate the breeding program for improved fruit quality and disease resistance.”
The fruit, which has fuzzy brown skin and green flesh and a taste similar to that of a strawberry, originated from the mountains of southwestern China and did not become known throughout the world until the 20th century. According to the researchers, it is a type of berry that, like grapes, grows on woody vines. The kiwifruit is a member of the order Ericales, a classification it shares with blueberries, tea bushes and Brazil nuts.
“The kiwifruit genome sequence represents the first of a member in the order Ericales, thus providing a valuable resource for comparative genomics and evolutionary studies,” said Fei. “We expect to continue generating genome sequences from other kiwifruit varieties to investigate the genetic diversity of kiwifruit and elucidate regulatory networks of important biological processes.”
The sequence is accessible online at the Kiwifruit Genome Database.