Abstract：In the process of plant regeneration mediated by developmental regulators, overexpression of developmental regulators could lead to pleiotropic effects such as developmental malformation and pollen abortion. Therefore, finding a suitable promoter to control the suitable expression of developmental regulators in plants may be one of the methods to obtain normal regenerated plants. LEAFY COTYLEDON2 (LEC2), a specific B3 transcription factor in plant embryogenesis, plays a crucial regulatory role in seed maturation. In the study, the results of semi-quantitative PCR showed that GbLEC2 was not or weakly expressed in roots, stems, leaves or embryogenic callus in Gossypium barbadense, but significantly highly expressed in globular embryo, torpedo embryo and cotyledon embryo. Bioinformatics analysis displayed that there were 2 seed-specific cis-elements Skn-1 element and RY repeat element in GbLEC2 promoter sequence. To further identify the transcriptional characters of GbLEC2 promoter, 4 different GbLEC2 promoter fragments including ProGbLEC2-1 (2000 bp), ProGbLEC2-2 (1500 bp), ProGbLEC2-3 (1000 bp) and ProGbLEC2-4 (500 bp) were constructed and then transformed into the different cotton tissues and cells by Agrobacterium-mediated transient transformation method. And the GUS activity assay demonstrated that ProGbLEC2-3 (1000 bp) and ProGbLEC2-4 (500 bp) promoter fragments displayed a specific transcriptional activity in somatic embryogenesis, which preliminarily met the Lowe's requirements for the promoters to drive suitable expression of developmental regulators in plant. Therefore, the GbLEC2 promoter fragment cloned in the study is expected to be a new candidate promoter to precisely regulate the expression of developmental regulators, and thus be applied to a novel molecular breeding technolody platform mediated by developmental regulators-promoting plant regenesis in G. barbadense.
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