A BELL1-Like Gene of Potato Is Light Activated and Wound Inducible

Abstract

BELL1-like transcription factors interact with their protein partners from the KNOTTED1 family to bind to target genes and regulate numerous developmental and metabolic processes. In potato (Solanum tuberosum), the BELL1 transcription factor StBEL5 and its protein partner POTH1 regulate tuber formation by affecting hormone levels. Overexpression of StBEL5 in transgenic lines produces plants that consistently exhibit enhanced tuber formation, and the mRNA of this gene moves through phloem cells in a long-distance signaling pathway regulated by photoperiod. Whereas photoperiod mediates the movement of StBEL5 RNA, activation of transcription of the StBEL5 gene in leaves is regulated by white light, regardless of photoperiod or light intensity. Illumination with either red or blue light induces the StBEL5 promoter, whereas far-red light had no effect. As expected, the StBEL5 promoter harbors numerous conventional light-responsive cis-acting elements like GT1, GATA, and AT1 motifs. Deletion constructs were analyzed to determine what sequences are involved in light activation. Transcriptional activity was also mediated by wounding on stems, insect predation on leaves, and photoperiod in stolons. These results demonstrate that StBEL5 gene activity in the leaf is correlated with wavelengths optimal for photosynthesis. The number of factors that affect the StBEL5 promoter supports the premise that the BELL1-like genes play a role in a wide range of functions.