Leonid Asipov vs
"Expression of cyanobacterial ictB in higher plants enhanced photosynthesis and growth"
Leonid Asipov, 2014
The aim of the original study(1) was to compare the photosynthetic properties of wt plants relative
to plants transgenic with ictB, protein which is considered to be involved in carbon transport in
cyanobacteria(2). The author of the original article have presented only partial data and exclusively
data which was convenient for his conclusions. The full data suggests no practical advantage for an
implementation of the transgenic protein in agriculture, since wt plants performed better at all the
"close to reality" CO2 concentration points(300-800 PPM).
For the sake of scientific truth, I will present the full data results and show how the author of the
original article has been misleading in his conclusions by presenting only partial data.
The original results : a single transgenic plant was presented
Fig 1: The original chart containing one transgenic plant vs an average of 7 wt plants.
Note that even the Y standard deviation of the wt plants was omitted.
The author has presented a single transgenic plant relative to average of 7 wt plants (Fig 1). Many
more transgenic plants were sampled and some of them were similar to wt, some few were better
and some were worse photosynthetically (Fig 2).
Fig 2: Presentation of all the data. Ci vs Photosynthesis curve. Dark green represents wt
Fig 3 : Average series of wt and transgenic plants. Ci vs Photosynthesis curve. Transgenic
N=31 wt N=7.
The wt plants are better at all points except the first three (50, 100 and 200 PPM). At 200 PPM,
there are no visible differences between wt and the transgenic plants.
In the following chart the photosynthetic properties of transgenic and wt plants has been statistically
compared. The T test was calculated for each [CO2] point separately.
Fig 4: Statistical T test of photosynthesis values at every [CO2] point separately.
In the first two points (50 and 100 PPM) the differences between wt and transgenic plants are
significant but meaningless since the photosynthesis value is very close to or less than 0.
The CO2 concentration on the first two points (50 and 100 PPM [CO2]) is insufficient for plants
growth(3) and therefore, the differences in the photosynthesis rate of plants are not practical.
At 300, 400, 600 and 800 PPM [CO2], wt plants photosynthesise significantly better than the
Fig 5 : Citations from the original article(1).
The author of the original article(1) claims that the transgenic plants photosynthesise better
"under limiting but not under saturating CO2 concentrations" and therefore the protein “can be used
as crop yield stimulator". To be precise, the only [CO2] point with positive photosynthesis at which
the transgenic plants are significantly better than wt is 100 PPM [CO2]. The average photosynthesis
rate of the transgenic plants at this point is 0.35 umol CO2 m-2 s-1, value which is too low for
healthy plant growth. At normal earth atmosphere CO2 concentration (around 400 PPM), wt plants
photosynthesise significantly better(Fig 4) and therefore there is no practical use
of the transgenic protein as "crop yield stimulator".
The plants growth experiments
Fig 6: RH of the chamber during the experiment. The RH is “low humidity” according to the
original article(Fig 7).
The authors' results suggest that at lower humidity, transgenic plants grow better than wt. Such
results are inconsistent with the gas exchange results, which report significantly better wt
photosynthesis at 400 PPM [CO2] (Fig 8), concentration at which all the plants were grown. Since,
the photosynthesis of wt plants is higher, the growth is expected to be as well.
Fig 7: Citation from the original article (1). “Low humidity” is considered to be less than
All the experiments were conducted at RH of less than 22% (Fig 6), value which is considered,
according to the article, as "low humidity" (1). According to the presented results, at such humidity
the transgenic plants grow better. Such declaration is not observed in the gas-exchange results
II Generation of plants
This part of the experiment was not published or mentioned in the original article. The best
transgenic plants were grown for another generation and sampled similarly to generation I.
Fig 7 : Ci vs Photosynthesis generation II. All the plants.
To compare the photosynthesis values only, an External [CO2] vs photosynthesis chart was built.
Fig 8: External [CO2] vs Photosynthesis curve of II generation.
Average series. Transgenic N=21 wt N=9.
The results suggest that there are no significant differences between the transgenic plants and wt.
Since the best transgenic plants did not pass their good properties to their progeny, I suggest that
their better properties at generation I were observed due to measurement inaccuracies and not due to
better genetics. Results of both generations suggest that wt plants photosynthesise equally to or
better than the transgenic at all points except 50 and 100 PPM [CO2]. Values which are too low for
normal plant growth.
The author of the original article has hidden data and presented false conclusions. The wt plants
photosynthesise better at the normal atmosphere [CO2] concentration (Fig 4 and Fig 7). This is the
reason why the transgenic protein is not practical for implementation in agriculture.
Materials and Methods
All measurements were made on LICOR LI6400 Portable Photosynthesis System.
The illumination levels were 500 uE. All the plants were well watered before measurement.
All the raw data of this article (LI6400 files) can be downloaded at :
(1) Expression of cyanobacterial ictB in higher plants enhanced photosynthesis and growth.
Judy Lieman-Hurwitz, Leonid Asipov, Shimon Rachmilevitch, Yehouda Marcus, Aaron Kaplan.
Plant Responses to Air Pollution and Global Change, 2005, pp 133-139
(2) A putative HCO3- transporter in the cyanobacterium Synechococcus sp. strain PCC 7942.
D J Bonfil; M Ronen-Tarazi; D Sültemeyer; J Lieman-Hurwitz; D Schatz; A Kaplan
FEBS letters, volume 430. Jul 2008.
(3) Plant responses to low [CO2] of the past.
Laci M. Gerhart and Joy K. Ward
New Phytologist, volume 188 Issue 3, Sep 2010.