GM petunia geneticist says modified ornamentals are likely to become more widespread

The origins of the GM orange petunia, which hit worldwide headlines in May after scientists found the unauthorised plants in the supply chain, come from a 30-year old experiment by a professor now at the University of Leeds.

Petunia 'African Sunset' - image: Flickr/FD Richards
Petunia 'African Sunset' - image: Flickr/FD Richards

In a December 1987 Nature paper, a team led by plant geneticist Peter Meyer, then with the Max Planck Institute for Plant Breeding Research in Cologne, Germany, but now at University of Leeds in the UK, showed that inserting a maize gene into a petunia enabled it to produce the pigment pelargonidin a characteristic orange colour.

Almost 30 years later, after the first interception of unauthorised GM ornamentals, in popular bedding plant the petunia, thousands of plants are now having to be thrown away in Europe and the US after the experimental gene found its way into breeding programmes.

The 30,000 petunias that the team planted in a trial were the first transgenic plants released into the field in Germany.

S&G Seeds, an affiliate of the Dutch seed company Zaadunie, licensed the technology, developing an orange commercial petunia by 1995. Rogers NK, also collaborating with Zaadunie, gained clearance from US regulators for an orange petunia field trial in Florida.

Biotech conglomerate Sandoz, which owned Zaadunie when the GM petunia was first developed, merged to form Novartis in 1996, which then joined its agribusiness with AstraZeneca’s in 2000 to form Syngenta.

It is not yet known how the GM petunias entered the supply chain. It is possible it had been around for a decade before Finnish biologist Teemu Teeri picked some orange petunias in Helsinki he suspected were GM leading Finnish food agency Evira to establish they were.

Breeders in Europe and the USA have thrown away thousands of plants across more than 20 varieties that are illegal for sale because they are unlicensed.

Plants for Europe's Graham Spencer has told Horticulture Week that the transgene has spread through other petunia breeding, probably originating from Petunia ‘African Sunset’. 

Horticulture Week asked Professor Meyer about GM petunias' origin and the future of GM ornamental plants.

Back in 1987, what did you see as the advantages of creating the new colour in petunias?

In 1987, there were no marker genes that allowed us to follow the activity of a transgene without destroying the plant. The maize A1 gene, when transferred and expressed in a petunia with white flower colour, triggered the production of an orange pigment.

What did you hope would happen to the new petunias?

This gave us the opportunity to follow the activity of the A1 transgene in every floral cell during a growing session and over several generations. This analysis helped us to discover conditions that render the transgene inactive via an epigenetic silencing mechanism that did not change the transgene DNA but its accessibility to the transcriptional machinery. (See link to 1992 paper Endogenous and environmental factors influence 35S promoter methylation of a maize A1 gene construct in transgenic petunia and its colour phenotype)

How do you think they got into the supply chain?

The transgenic plants were able to produce an orange flower colour but were not suitable to be marketed as the flowers were too small and the transgene could be silenced. A breeding company therefore used the plants to improve colour intensity and stability (see Oud et al 1995). I am not an expert on plant breeding but I understand that it is common practice for breeders to use material, including plants from competitors, to breed new varieties. I therefore assume that breeders have used orange petunia lines to produce new varieties, probably without even realising that they were including a transgenic line in their breeding programmes.

What do you think the future for GM in ornamentals is?

"GM technologies are now widely accepted across the world with the exception of most EU countries. I therefore assume that in the future some new ornamental varieties will include traits induced via GM technologies, especially those that help the plants to cope with biotic and abiotic stress, and that produce new shapes, colour or other features."

Could there be another finding of GM in another ornamental crop?

"I would not exclude this possibility considering that is appears to be common practice for breeders to use foreign material. Plants that contain a transgene could probably be identified on the basis of the vector or promoter sequences associated with the transgene. The new CRISPR/Cas technology, however, only induces small mutations or modification that will be very difficult to identify. It would therefore make sense to assess new ornamentals and crops not on the basis if they are a GM lines or if they are derived from a GM line, but on the basis of the characteristics of the plant. It does not seem to make sense to assess which technology has been used to produce a plant as this says nothing about the features of the plant – this seems to be as useless as assessing the quality of a book on the basis that it was written on a typewriter or on a computer."

Meyer’s 1987 paper said: "Petunia hybrida is one of the classical subjects of investigation in plants in which the pathway of anthocyanin biosynthesis has been analysed genetically and biochemically. In petunia cyanidin- and delphinidin-derivatives, but no pelargonidin-derivatives are produced as pigments. This is due to the substrate specificity of the dihydroflavonol 4-reductase of petunia, which cannot reduce dihy-drokaempferol. The petunia mutant RL01, which accumulates dihydrokaempferol, shows no flower pigmentation. RL01 served as a recipient for the transfer of the A 1 gene of Zea mays encoding dihydroquercetin 4-reductase, which can reduce dihydrokaempferol and thereby provided the intermediate for pelargonidin biosynthesis. Transformation of RL01 with a vector p35Al, containing the A 1-complementary DNA behind the 35S promotor leads to red flowers of the pelargonidin-type. Thus a new flower pigmentation pathway has been established in these plants."

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