AGV-PY2Ø3-4 - GRAINZYME corn | BCH-LMO-SCBD-115832 | Living Modified Organism | Biosafety Clearing-House


Living Modified Organism (LMO)

Decisions on the LMO Risk Assessments  
last updated: 04 Dec 2020
Living Modified Organism identity
The image below identifies the LMO through its unique identifier, trade name and a link to this page of the BCH. Click on it to download a larger image on your computer. For help on how to use it go to the LMO quick-links page.
GRAINZYME corn is a maize modified to express an engineered Escherichia coli phytase gene in the kernels of the maize. Phytase expression improves the digestibility of the feed products by catalyzing the hydrolysis of phytate. In seeds (such as maize kernels), phosphorous is stored in the form of phytate (phosphate group), which is an anti-nutrient because it chelates minerals, such as iron, zinc, magnesium and calcium. Thus, phytase improves the overall digestibility and increases the bioavailability of phosphorous in the maize. Secondly, the expression of phytase may also reduce the excreted phosphorous in manure and therefore decrease phosphorous eutrophication in the environment. The engineered protein contains specific amino acid changes to confer enhanced thermotolerance and resilience to gastric digestion. The modified maize additionally contains an E. coli phosphomannose isomerase cassette for mannose selection during transformation.
The term “Recipient organism” refers to an organism (either already modified or non-modified) that was subjected to genetic modification, whereas “Parental organisms” refers to those that were involved in cross breeding or cell fusion.
Maize line 'High II B' (T940B)
Characteristics of the modification process
  • Agrobacterium-mediated DNA transfer
Some of these genetic elements may be present as fragments or truncated forms. Please see notes below, where applicable.
Gene cassettes and expression
The insert from pAG4758 contains three Escherichia coli phytase (phy02) and one E. coli phosphomannose isomerase (pmi) gene cassettes.

The first phy02 cassette is under transcriptional control of an Oryza sativa glutelin-1 promoter and an Agrobacterium tumefaciens nopaline synthase (nos) terminator. The second is under transcriptional control of Zea mays zein Zc2 (28 kDA glutelin-2) promoter and nos terminator. The third phy02 sequence is under control of the Z. mays globulin-1 promoter and nos terminator. Transcripts from all three cassettes are expected to contain (from 5' to 3'): Z. mays signal peptide from 27 kDa γ-zein seed storage protein (to direct protein to endoplasmic reticulum (ER)), phy02 and the synthetic SEKDEL ER retention peptide. The promoters specify high levels of embryo/seed-specific expression of phy02.

Transcription of pmi is under control of the Z. mays ubiquitin 1 promoter and nos terminator. The ubiquitin promoter is expected to achieve high levels of constitutive expression in all plant tissues.

- phy02 was derived from the E. coli appA (native phytase) through site-directed mutagenesis for increased thermotolerance and resilience to gastric digestion. The amino acid changes did not impact the structure or biological function of the protein (see attached document '19_17601p' for more information).
- Southern blot, genome walking and segregation analyses indicated that two independent T-DNA insertions occurred in the PHY203 genome:
-- One locus was inserted into chromosome 8 in a region with no defined gene or genetic element. This insertion was intact, containing all gene cassettes.
-- The other locus was inserted into chromosome 2 into a 99 nucleotide unannotated open reading frame that was predicted to unlikely correspond to a functional gene. The T-DNA insertion is incomplete, being truncated in the Globulin-1 promoter (only two phy02 cassettes under control of the rice glutelin and zein Zc2 promoters are present).
- No vector backbone was detected in the PHY203 genome.
LMO characteristics
  • Feed
Detection method(s)