DP-Ø56113-9 - Seed Production Technology for Africa maintainer maize | BCH-LMO-SCBD-258926 | Living Modified Organism | Biosafety Clearing-House
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Living Modified Organism (LMO)

Decisions on the LMO Risk Assessments  
last updated: 19 Jan 2022
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.
Seed Production Technology for Africa maintainer maize
EN
DP56113
Yes
DP-Ø56113-9
The maize (Zea mays) was modified to restore fertility to male-sterile maize lines and to facilitate hybrid maize seed production. The parental line is homozygous for the male-sterile Ms44 gene. To restore male-fertility, the maize expresses an artificial microRNA cassette to silence the Ms44 and sllow for pollen production. To produce the male-sterile female hybrid lines for further seed production, the maintainer line is used as a pollinator. Pollen carrying the introduced constructs expresses maize alpha-amylase, which depletes the starch reserves in the nascent pollen and prevents germination. Therefore, the pollen that germinates does not contain introduced genetic elements and creates female parents carrying the male sterility gene Ms44. These female parents can then be used for further hybrid seed production, eliminating the need to de-tassel as self-fertilization is not possible. The maintainer maize additionally expresses as fluorescent marker DsRed2, which is allows for visual selection of modified kernels during the production of the parental lines.
EN
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.
Pioneer proprietary inbred line PHH5G
EN
  • BCH-LMO-SCBD-105060-1
    DP-32138-1 - 32138 SPT Maintainer
    | Pioneer Hi-Bred International Inc. | Changes in physiology and/or production (Reproduction, Male sterility), Selectable marker genes and reporter genes
Characteristics of the modification process
PHP70533
EN
  • Agrobacterium-mediated DNA transfer
Some of these genetic elements may be present as fragments or truncated forms. Please see notes below, where applicable.
The modified maize contains three gene cassettes: maize alpha-amylase (aa1, amy); Discosoma sp. DsRed2 and maize male-sterile Ms44 artificial microRNA (ms44-amiRNA).

The amy coding sequence is under control of the maize pollen polygalacturonase promoter and a maize In2-1 terminator. A maize brittle 1 transit peptide is also included between the amy sequence and the promoter. The transit peptide targets AMY to the amyloplast. The pollen polyglacturonase promoter is expected to restrict the expression of amy to pollen tissues during late-stage (after first mitotic division) development.

The DsRed2 coding sequence is under control of a Hordeum vulgare lipid transfer protein 2 promoter and a Solanum tuberosum proteinase inhibitor II terminator. A Cauliflower mosaic virus enhancer was also added to the the promoter to further enhance gene expression of the downstream sequences.

The ms44-amiRNA sequence is under control of the maize ms44 promoter and terminator. The sequence will have the following (5' to 3'): 5' precursor sequence of the miRNA backbone 396h; ms44-amiRNA; precursor miRNA backbone 396h; Ms44 star sequence and 3' precursor sequence of the miRNA backbone 396h. After transcription the ms44-amiRNA sequence will base pair with the Ms44 star sequence and form a hairpin structure. This secondary structure will trigger an RNA interference response to silence the expression of Ms44. Thus, the hairpin RNA will not be translated into protein. For more information on gene silencing, kindly refer to the "Other gene(s) whose expression was affected by the transformation" section below.

Note:
  • The initial T-DNA insertion contain six gene cassettes: Ms44 amiRNA; amy; DsRed2; wus2; odp2 and maize-optimized cre. After T-DNA insertion, cre recombination of loxP sites within the T-DNA removes the wus2, odp2, and mo-cre gene cassettes. These cassettes enhance tissue regeneration after transformation.
  • Southern-by-Sequencing analysis indicated that a single, intact insertion of T-DNA is present in the genome without integrate of backbone sequencing.
  • Southern blot and restriction enzyme digestion analyses indicated the insert was stable over multiple generations.
EN
LMO characteristics
The ms44-amiRNA transcript will contain (5' to 3'): 5' precursor sequence of the miRNA backbone 396h; ms44-amiRNA; precursor miRNA backbone 396h; Ms44 star sequence and 3' precursor sequence of the miRNA backbone 396h. After transcription the ms44-amiRNA sequence will base pair with the Ms44 star sequence and form a hairpin structure. This hairpin RNA is processed by Dicer-like endonucleases into small interfering RNAs of ~21 to 22 nucleotides in length. The small interfering RNAs will then be recruited by Argonaute proteins to target mRNA molecules with complementary to the small interfering RNA sequence for silencing. Thus, since the ms44-amiRNA sequence is complementary to the endogenous ms44 and mutant Ms44 transcripts, their expression will be silenced.
EN
  • Other (Hybrid seed production)
Detection method(s)
EN

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