GM crops go through multi-location field trials to analyze the agronomics,
composition, and the concentration of transgenic proteins, which is a main
consideration in safety assessment of GM crops. Reference proteins are
expected to maintain a relatively stable expression pattern in healthy
plants given their function in various cellular functions. Understanding the
effects of genotype, growth stage, and location on reference proteins may
provide insight into the contribution these factors could have on transgenic
protein concentrations in GM crops. Thus, scientists from India, USA, and
Thailand studied the concentrations of three endogenous proteins (actin,
elongation factor 1-alpha, and glyceraldehyde 3-phosphate dehydrogenase) in
several different maize hybrids grown across multiple field locations over
two years.

The researchers collected leaf samples from healthy plants from different
developmental stages across the growing seasons. Results of the
enzyme-linked immunosorbent assay (ELISA) showed that the concentrations of
the three proteins were relatively consistent across hybrid backgrounds,
when compared within one growth stage and location (2-26%CV), whereas the
concentrations of proteins in the same hybrid and growth stage across
different locations were more variable (12-64%CV). In general, the protein
concentrations in the two years of study showed similar trends in
variability.

According to the researchers, some degree of variability in protein
concentrations was expected for both transgenic and endogenous
plant-expressed proteins. In the case of GM crops, the potential variation
in protein concentrations due to location effects is captured in the current
model of multi-location field testing.

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