Cloning and promoter activity analyses of the promoter of 2'-deoxymugineic acid (DMA) secretion channel gene YS3 in maize.

Iron (Fe) deficiency is a world-wide serious agricultural problem. Maize secretes 2'-deoxymugineic acid (DMA) to uptake and utilize Fe from the soil. In order to explore the gene expression patterns of the DMA secretion channel gene YS3, we cloned the 2813 bp YS3 promoter, and constructed the plant expression vector pCAMBIA-YS3GUS. The promoter contains a lot of TATA-boxes and CAAT-boxes, and cis-acting regulatory elements such as the light responsive elements and the hormone responsive elements. Arabidopsis was transformed via Agrobacterium tumefacients-mediated procedures to obtain the pYS3::GUS transgenic plants, which were confirmed by GUS staining. Then, the stained tissue was observed using paraffin section methods and the YS3 promoter activity was also analyzed. We found that the promoter could drive GUS gene expression specifically in the root epidermal cells. Mechanical damage could activate the promoter, and drive the GUS gene expression adjacent to the damage sites. Our results provide a molecular basis to understand the DMA secretion process in maize.

Pollen flow of wheat under natural conditions in the Huanghuai River Wheat Region, China.

The transgenic pollen spread is the main pathway of transgenic plant gene flow. The maximum distance of pollen dispersal (horizontal), the spatial dynamics of pollen movement (vertical), and the patterns of pollen dispersal are important considerations in biosafety assessments of genetically modified crops. To evaluate wheat (Triticum aestivum) pollen dispersal, we measured the pollen suspension velocity and analyzed pollen dispersal patterns under natural conditions in the Huanghuai River wheat-growing region in 2009. The pollen suspension velocity was 0.3-0.4 m/s. The highest pollen densities were detected in the north, northwest, and south of the pollen source. Pollen was dispersed over distances greater than 245 m in the northwest and northeast directions. At the pollen source center, pollen density decreased with increasing vertical height. In the north of the pollen source, the pollen density from 65 m to 225 m showed a wave-mode decrease with increasing height. The horizontal transport of pollen over longer distances fitted polynomial equations. In the north, the pollen density was highest at 45 m from the pollen source, and decreased with increasing distance. In the northwest, the pollen density showed a double-peak trend. In the northeast, pollen density was highest from 45 m to 125 m from the source. Wind speeds greater than the pollen suspension velocity and the duration of continuous gusts were the main factors affecting pollen dispersal. This information will be useful for determining the spatial isolation distances for hybrid seed production and for the commercial production of transgenic wheat.

[Study on the relationship between inheritance and immature embryo culturing capacity of maize inbreds].

The immature embryo culturing capacity of maize is crucially important to maize improvement by transgenic approach. The hereditary variation regularity of maize embryo culturing capacity is not very clear yet. The research aims to study the relationship between inheritance and immature embryo culturing capacity of maize inbreds. By culturing immature embryos of 22 maize inbreds, embryonic callus induction efficiency and regenerating plant efficiency were analyzed with cluster analysis method. And the genetic relationships of 22 inbreds were analyzed using 14 SSR primers with good polymorphism. Results showed that 22 inbreds were classified into three groups. The average embryonic callus efficiency and regenerating plant efficiency of the inbreds with good culturing capacity were 85.0% and 86.7% respectively. The average embryonic callus efficiency and regenerating plant efficiency of the inbreds with middle culturing capacity were 41.3% and 53.1% respectively. The average embryonic callus efficiency and regenerating plant efficiency of the inbreds with bad embryo culturing capacity were 2.14% and 2.75% respectively. 22 inbreds were clustered based on 110 polymorphic loci and classified into 4 genetic groups based on GS (genetic similarity) = 0.75. The consistencies were 91%, 82% and 91% for the clustered results of the single character (embryogenic callus efficiency and regenerating plant efficiency) and both characters respectively. t test showed that immature embryo culturing capacity was significantly different between different genetic groups. Therefore, the immature embryo culturing capacity could be correctly estimated by polymorphic loci from the 14 SSR primers. The clustering method by the SSR provided a basis for forecasting and selecting the immature embryo culturing capacity of maize inbreds.