Expression of Phytase gene in transgenic maize with seed-specific promoter 27-kDa γ Zein and constitutive promoter CaMV 35S

Phytase enzymes are applied to animal feed to help animals absorb more nutrients. The use of feed raw materials containing phytase enzymes is expected to reduce the cost of animal feed production. Efforts to increase the phytase content in maize were carried out by improving genetics, in the way of assembling transgenic plants containing high phytase content. The 27-kDa γ Zein promoter is a specific promoter that expresses genes in caryopsis, and promoter CaMV 35S is a constitutive promoter that controls gene expression in all tissues and generally does not depend on the growth phase. Transgenic maize was transformed using Agrobacterium tumefacien infection method on maize B104. The reverse transcriptase polymerase chain reaction (RT-PCR) approach was used to examine the expression of phytase genes in leaves, roots, and caryopsis was done 10, 20, and 30 days after pollination (DAP). The phytase enzyme activity test was also carried out by using the colorimetric phosphomolybdate analysis method to see the phytase enzyme activity in unit µg-1. The results showed that the phytase gene in transgenic plants with the 27-kDa γ Zein promoter was highly expressed in maize caryopsis, but in line Z6.10 was also expressed in leaves, while in the CaMV 35S promoter the phytase gene was only expressed on the leaves. Phytase enzyme activity showed that transgenic maize was higher than non-transgenic maize.

Overexpression of the ZmSAMDC Enhances Cold Tolerance in Transgenic Maize (Zea Mays L.)

Maize (Zea mays L.) is a food crop sensitive to low temperatures. Low temperature, as one of the abiotic stress hazards, seriously affects the yield of corn. However, the genetic basis of low-temperature adaptation in maize is still poorly understood. In this study, maize S-adenosylmethionine decarboxylase (SAMDC) was localized on the nucleus. We introduced the SAMDC gene into the excellent maize inbred line variety GSH9901 and used Agrobacterium-mediated transformation to produce cold-tolerant transgenic maize lines. After a 3-year single-location field trial, the contents of polyamine (PA), proline, malondialdehyde, an antioxidant enzyme, and APX in the leaves of transgenic maize plants overexpressing SAMDC were significantly increased, and the introduction of the SAMDC gene was significantly increased the expression of CBFs and cold-related genes.The agronomic traits of overexpression maize changed and the yield traits were significantly improved, but no significant changes were found in plant height, ear length, and shaft thickness.Thus, engineering the SAMDC enzyme is an effective strategy to improve the cold tolerance and value of maize.

Relationship between Maize Seed Productivity in Mexico between 1983 and 2018 with the Adoption of Genetically Modified Maize and the Resilience of Local Races

Mexico depends on maize imports to satisfy its national demand. The use of native maize varieties among subsistence farmers can help to reduce the cereal’s imports. However, the agricultural policy in Mexico to improve the productivity per hectare has centered on the use of improved varieties; among them, the transgenic variety. In this study, the maize productivity in Mexico from 1983 to 2018 was analyzed to determine the influence of agricultural policies in the sector, and the factors that condition the adoption of transgenic maize. It was found that the agricultural policy improved the productivity of those regions with irrigation; however, for rainfed regions, the expected technological changes were not achieved because the ancestral tradition in cultivation, associated with the greater variety of native maize and to a larger indigenous population, was stronger. The adoption of transgenic maize also had low significance in the rainfed regions, since the increase in field yields is not economically profitable with regards to the increase in production costs. Therefore, the agricultural policy to increase productivity ought to be directed at the protection of subsistence farmers, revaluing the use of native varieties that have shown higher resilience to technological and environmental changes.

Using Combined Methods of Genetic Mapping and Nanopore-Based Sequencing Technology to Analyze the Insertion Positions of G10evo-EPSPS and Cry1Ab/Cry2Aj Transgenes in Maize

The insertion position of the exogenous fragment sequence in a genetically modified organism (GMO) is important for the safety assessment and labeling of GMOs. SK12-5 is a newly developed transgenic maize line transformed with two trait genes [i.e., G10evo-5-enolpyrul-shikimate-3-phosphate synthase (EPSPS) and Cry1Ab/Cry2Aj] that was recently approved for commercial use in China. In this study, we tried to determine the insertion position of the exogenous fragment for SK12-5. The transgene–host left border and right border integration junctions were obtained from SK12-5 genomic DNA by using the thermal asymmetric interlaced polymerase chain reaction (TAIL-PCR) and next-generation Illumina sequencing technology. However, a Basic Local Alignment Search Tool (BLAST) analysis revealed that the flanking sequences in the maize genome are unspecific and that the insertion position is located in a repetitive sequence area in the maize genome. To locate the fine-scale insertion position in SK12-5, we combined the methods of genetic mapping and nanopore-based sequencing technology. From a classical bulked-segregant analysis (BSA), the insertion position in SK12-5 was mapped onto Bin9.03 of chromosome 9 between the simple sequence repeat (SSR) markers umc2337 and umc1743 (26,822,048–100,724,531 bp). The nanopore sequencing results uncovered 10 reads for which one end was mapped onto the vector and the other end was mapped onto the maize genome. These observations indicated that the exogenous T-DNA fragments were putatively integrated at the position from 82,329,568 to 82,379,296 bp of chromosome 9 in the transgenic maize SK12-5. This study is helpful for the safety assessment of the novel transgenic maize SK12-5 and shows that the combined method of genetic mapping and the nanopore-based sequencing technology will be a useful approach for identifying the insertion positions of transgenic sequences in other GM plants with relatively large and complex genomes.