Development of a simple and efficient system for excising selectable markers in Arabidopsis using a minimal promoter::Cre fusion construct

Confirmation of 'Pollen- and Seed-Specific Gene Deletor' System Efficiency for Transgene Excision from Transgenic Nicotiana tabacum under Field Conditions

The commercial application of genetically modified plants has been seriously impeded by public concern surrounding the potential risks posed by such plants to the ecosystem and human health. Previously, we have developed a 'pollen- and seed-specific Gene Deletor' system that automatically excised all transgenes from the pollen and seeds of greenhouse-grown transgenic Nicotiana tabacum. In this study, we conducted seven field experiments over three consecutive years to evaluate the stability of transgene excision under field conditions. Our results showed that transgenes were stably excised from transgenic Nicotiana tabacum under field conditions with 100% efficiency. The stability of transgene excision was confirmed based on PCR, as well as the GUS staining patterns of various organs (roots, leaves, petiole, stem, flower, fruit, and seeds) from transgenic N. tabacum. In six transgenic lines (D4, D10, D31, D56, and D43), the transgenes were stably deleted in the T0 and T1 generations. Thus, the 'Gene Deletor' system is an efficient and reliable method to reduce pollen- and seed-mediated unintentional gene flow. This system might help to alleviate the food safety concerns associated with transgenic crops.

Cloning and characterization of two EcR isoforms from Japanese pine sawyer, Monochamus alternates

The ecdysone receptor (EcR) is the hormonal receptor of ecdysteroids, which regulates insect growth and development. In this study, we cloned and characterized two isoforms of EcR in Monochamus alternates named MaEcR A and MaEcR B. The cDNAs of MaEcR A and MaEcR B have open repeating frames of 1,695 and 1,392 bp, respectively. The deduced proteins have the same C-terminal sequence and varied in N-terminal, and are consistent with reports on other insect species, particularly with the receptor of another coleopteran, Tribolium castaneum. The isoform-specific developmental expression profile of EcR in the epidermis and the midgut were analyzed with quantitative real-time reverse-transcriptase polymerase chain reaction in the pupal stage. RNA interference (RNAi) with common or isoform-specific regions induced developmental stagnation. When treated in the later larval stage, RNAi with either the common sequence or an EcR A specific sequence caused more severe effects and most larvae died prior to adulthood. The EcR B specific sequence caused less severe effects and about half of the treated larvae became adults, but some showed developmental defects. RNAi with both isoforms at early pupal stage attenuated the expression of 20E-regulated genes E74, E75, and HR3. The study demonstrates the role of EcR in the transduction of ecdysteroid response in Monochamus alternatus.