A team of scientists from the United States and China has sequenced the genome of kiwifruit (Actinidia chinensis).
Kiwifruits. Image credit: Hiperpinguino / CC BY-SA 3.0.
Kiwifruit, or kiwi, is a cylindrical and egg-shaped berry with reddish-brown skin which is covered in short hairs. The fruit originated from the southwestern China and was not really known to the world until the early 20th century, when farmers in New Zealand discovered the fruit and began breeding it as a commercial crop.
For the sequencing of kiwifruit genome, the team used a Chinese variety called Hongyang. They then compared kiwifruit to the genomes of other representative plant species including tomato, rice, grape and the mustard weed Arabidopsis, and identified about 8,000 genes common among all five species.
The data also reveal 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.
When genes are duplicated, the extra genes can mutate to perform entirely new functions that were not previously present in the organism. This process, called neofunctionalization, can occur with no adverse effects in plants and, in the case of kiwifruit, was quite beneficial.
“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,” explained Dr Zhangjun Fei from Cornell University, who is the senior author of a paper published in the journal Nature Communications.
Prior to this study, extensive research on the metabolic accumulation of vitamin C, carotenoids and flavonoids had been reported in kiwifruits, but genome sequence data, critical for its breeding and improvement, had never been available.
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Bibliographic information: Shengxiong Huang et al. 2013. Draft genome of the kiwifruit Actinidia chinensis. Nature Communications 4, article number: 2640; doi: 10.1038/ncomms3640
