WASHINGTON, Aug. 30 (Xinhua) -- Chinese, British and Australian scientists have determined the DNA code of the opium poppy genome, uncovering key steps in how the plant evolved to produce the pharmaceutical compounds used to make vital medicines.

The study published on Thursday in the journal Science may pave the way for scientists to improve yields and the disease resistance of the medicinal plant, securing a reliable and cheap supply of the most effective drugs for pain relief and palliative care.

The scientists from the University of York and Wellcome Sanger Institute in the United Kingdom together with colleagues from Xi'an Jiaotong University and Shanghai Ocean University in China and Sun Pharmaceutical Industries (Australia) Pty Ltd, produced a high quality assembly of the 2.7 Giga-Base genome sequence distributed across 11 chromosomes.

The findings revealed the origins of the genetic pathway leading to the production of the cough suppressant noscapine and painkiller drugs like morphine and codeine.

It enabled the researchers to identify a large cluster of 15 genes that encode enzymes involved in two distinct biosynthetic pathways involved in the production of both noscapine and the compounds leading to codeine and morphine.

According to the researchers, plants have the capacity to duplicate their genomes and when this happens the duplicated genes can evolve to develop new machinery to make a diverse array of chemical compounds that are used to defend against attack from harmful microbes and herbivores and to attract beneficial species such as bees to assist in pollination.

The genome assembly revealed the ancestral genes that came together to produce the a kind of gene fusion that is responsible for the first major step on the pathway to morphine and codeine.

This fusion event happened before a relatively recent whole genome duplication event in the opium poppy genome 7.8 million years ago, according to the study.

The paper's co-corresponding author Professor Ye Kai from Xi'an Jiaotong University said: "It is intriguing that two biosynthetic pathways came to the same genomic region due to a series of duplication, shuffling and fusion structural events, enabling concerted production of novel metabolic compounds."