Red fluorescent protein (DsRed2), an ideal reporter for cotton genetic transformation and molecular breeding

Genes encoding reporter proteins are used as visual marker-assisted tools in genetic transformation as well as plant breeding. In this study, the red fluorescent protein identified in Discosoma sp. coral (DsRed2) was successfully used as a visual marker for cotton genetic engineering. DsRed2 was successfully expressed in two cotton cultivars, JIN668 and YZ1, driven by the CaMV-35S promoter via the Agrobacterium-mediated transformation. Our results suggest that DsRed2 expression provides an early-stage selection tool for the transgenic calli via visual observation. Red fluorescence can be detected not only in callus and somatic embryos but also in most tissues and organs of mature plants. The transgenic line Yz-2-DsRed2 was crossed with four different cotton cultivars to assess the transgene heritability and stability in different genetic backgrounds. The heritability of the red color was highly stable when Yz-2-DsRed2 was used as a male parent. The DsRed2 gene expressed 100% in the F1 hybrids. To investigate the relationship between DsRed2 transcription and DNA methylation, a methylation-specific PCR approach was applied to the CaMV-35S promoter region. The results showed a negative association between DNA methylation level in the promoter region and the transgene transcription. Taken together, these findings suggest DsRed2 a visual reporter gene for cotton genetic transformation and molecular breeding programs.