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Breeding apples with red flesh

28 Aug 2009

Plant & Food scientist recognised for most commercially-applicable finding

(To view Richard Espley's MacDiarmid Award video click here)

Dr Richard Espley, a molecular biologist at Plant & Food Research, has been named one of the MacDiarmid Young Scientists of the Year for his work in apple genetics.

Dr Espley was named winner of the Adding Value to Nature category of the awards, and was also recognised with the Commercialisation Award for research that showed the most potential for commercial application.

Dr Espley, who has recently completed his PhD at the University of Auckland, is conducting research into the genetic mechanisms which control the red colour of apples. This discovery will help in breeding apples that have novel colour characteristics and are high in healthy anti-oxidants.

The mechanism he discovered involves a natural alteration in the DNA of the gene that controls colour in apple, MYB10. This MYB10 gene is a transcription factor, a class of genes that produce proteins which bind to other genes and switch them on or off. In this case, MYB10 results in a protein that switches on genes in the anthocyanin production pathway, producing the red colour of apple.

The alteration involves multiple repeats of a protein binding sequence found in the promoter area of the MYB10 gene of ancient varieties of red-fleshed apples. In all apples, the MYB10 protein was found to bind its own promoter to regulate colour. However, in red-fleshed apples the multiple repeats in the promoter generate more opportunities for the MYB10 protein to bind its own DNA, causing strong positive feedback and a more active gene. Consequently, the MYB10 protein is produced at high levels, activating the other genes it controls, producing substantial levels of anthocyanin throughout the plant.

The research was published in the prestigious journal The Plant Cell earlier this year.

Dr Espley says understanding how anthocyanin is regulated at the genetic level is important in understanding how to breed red apples that are more attractive to the consumer and contain high levels of healthy antioxidants.

"Red apples, with red flesh as well as red skin, occur naturally in the apple origin regions of Central Asia. However, these apples are normally quite bitter tasting so need to be crossed with flavoursome white fleshed apples to produce a commercially-viable, red-fleshed eating cultivar. Being able to screen for the red-flesh gene in seedlings will allow breeders to isolate and focus on new varieties of apple with red flesh characteristics at an early stage, speeding up the breeding process."

The MacDiarmid Young Scientists of the Year Awards are presented annually by the Foundation for Research, Science and Technology.

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