Science in Society Archive

GM Rice Unstable

Scientists at the UK top GM plant research institute, the John Innes Centre, claim they have evidence that transgenic rice lines are stable. Dr. Mae-Wan Ho shows how their claim is not borne out by their own evidence.

When we raised serious concerns over the safety of the cauliflower mosaic virus (CaMV) 35 S promoter, which is in practically all GM crops on release or on trial back in 1999 [1], we were fiercely attacked and dismissed. Scientists at the John Innes Centre (JIC) assured us that the CaMV 35S promoter is safe on grounds that people have been eating cabbages infected with the virus all the time. We have refuted this in at least two further publications [2,3], showing how the CaMV 35S promoter in the viral genome and the intact virus is not the same as the cutout promoter in GM constructs integrated into transgenic plants. For while the virus itself is specific to the cabbage family, the cutout promoter functions in all organisms, including frog eggs and human cells, which our critics apparently did not know about. But the JIC scientists have persistently failed to cite our papers or to reply to them.

In their latest annual report released earlier this year, some of the same scientists admitted that GM plants are unstable, and that the CaMV 35S promoter is a recombination hotspot which makes GM construct extra unstable, and should be phased out.

But when we drew people's attention to that [4], they issued a strong denial, attacked us again, and for ignoring evidence published in one of their papers [5] documenting that transgenic rice lines are stable. So I undertook to review that paper in detail.

I found that their data do not at all support their claim that the transgenic rice lines are stable. They have declined to reply to my review so far.

The paper is a report of studies on 40 independent rice lines representing 11 cultivars, each containing 2 or 3 different transgenes (not 3 or 4 as stated in the text) delivered by particle bombardment ('gene gun'). The transgenes were delivered either by cotransformation, ie, the genes in two or more different constructs in separate vectors, or in the form of cointegrate vector, ie, all three genes linked together in one vector. The authors claim the following.

1. "Approx. 75% of the lines (29/40) demonstrated Mendelian inheritance of all trangenes, suggesting integration at a single locus".

2. Levels of expression varied, but primary transformants showing high level expression of four of the transgenes, gna (snowdrop lectin), gusA (beta-glucuronidase), hpt (hygromycin resistance) and bar (tolerance to herbicide phosphin-othricin) "faithfully transmitted these traits to progeny".

3. In the case of transgenes cry1Ac and cry2A (insecticidal endotoxins from Bacillus thur-ingiensis or bt), "transgene expression was stably inherited when primary transformants showed moderate or low-level expression".

4. The results show that "six transgenes (three markers and three insect-resistance genes) were stably expressed over four generations of transgenic rice plants".

5. The results showed that "transgene expression was stable in lines of all the rice genotypes" analysed.

Now, claims 4 and 5 are contradicted by claims 1 to 3 which indicate that at least 25% of the lines did not show Mendelian inheritance, a sign of instability (and a weak one at that), and only some of the transformants gave stable expression in later generations. So we can dismiss claims 4 and 5 immediately, and concentrate on the first three. But even those are not borne out by the data presented. This seems to be a general problem with the paper. The text states what the data do not support.

The claim (in the title) that "multiple heterologous transgenes show similar behaviour in diverse genetic backgrounds" is unjustified, to say the least, as not all cultivars were transformed with the same genes or GM constructs.

There were numerous in-consistencies between the text and the data presented in the Tables and Figures.

A very loose interpretation of stability is used, based on the failure to significantly depart from the Mendelian ratios, but the genotypes of parental plants were not checked out with quantitative molecular techniques, as they should have been.

A generous interpretation of the data presented would suggest that at most 7 out of 40 (18%) transgenic rice lines may be stable to the R3 generation. In other words, 82% of the rice lines were unstable, and not 25% as claimed in the abstract of the paper.

(For the complete technical review, see Questionable 'Stability' at JIC, I-SIS website)

References

  1. Ho, M.W., Ryan, A. and Cummins, J. (1999). The cauliflower mosaic viral promoter - a recipe for disaster? Microbial Ecology in Health and Disease 11, 194-7.
  2. Ho, M.W., Ryan, A. and Cummins, J. (2000). Hazards of transgenic plants with the cauliflower mosaic viral promoter. Microbial Ecology in Health and Disease 12, 6-11.
  3. Ho, M.W., Ryan, A. and Cummins, J. (2000) CaMV 35S promoter fragmentation hotspot confirmed, and it is active in animals. Microbial Ecology in Health and Disease (in press).
  4. "Top research centre admits GM failure" ISIS News7/8, Feb. 2001

  5. Gahakwa D, Maqbool SB, Fu X, Sudhakar D, Christou P and Kohli A. Transgenic rice as a system to study the stability of transgene expression: multiple heterologous transgenes show similar be-haviour in diverse genetic backgrounds. Theor Appl Genet 2000: 101: 388-99.

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