In silico promoter analysis and expression of the BIG BROTHER gene in different organs of potato

The ubiquitin E3 ligase BIG BROTHER/ENHANCER OF DA1 (BB) gene encoding a RING finger protein was identified as a central growth regulator in Arabidopsis thaliana. It was found that BB restricts cell proliferation and promotes leaf senescence. Besides of Arabidopsis, however, the role and regulation of BB in other plant species is only sparsely known. Supposing that the BB gene, like in Arabidopsis, has an important role in the development of potato we aimed to analyse a 3.0-kb promoter sequence of the potato BB gene, StBB, in silico and study the level of StBB expression by quantitative reverse transcription PCR in different organs. A total of 48 binding sites for 15 transcription factor (TF) families were predicted. Most of them were located in the -1.5-kb promoter region. The dominating family of TFs was DOF. It was found that 20 out of the 24 TFs with known functions are involved in developmental processes such as for example, the flower-, leaf-, stem- and root development or cell cycle regulation. In line with this finding, the StBB mRNA was detected in each organ tested with the largest amounts in petal and stamen. These results suggest a similar function of StBB in potato than that is of BB in Arabidopsis, i.e., restriction of organ overgrowth during development and limitation of the plant growth.