Castelain M, Le Hir R, Bellini C
The non-DNA binding bHLH transcription factor PRE3/bHLH135/ATBS1/TMO7 is involved in the regulation of light signaling pathway in Arabidopsis
Physiol Plant. 2012 Jul;145(3):450-60


Plant basic Helix-loop-helix (bHLH) proteins are transcription factors that are involved in many developmental mechanisms, including light signaling and hormone homeostasis. Some of them are non-DNA binding proteins and could act as dominant negative regulators of other bHLH proteins by forming heterodimers, in a similar way to animal Inhibitor of DNA binding proteins. It has been recently reported that several non-DNA binding bHLHs are involved in light signaling (KDR/PRE6), gibberellic acid signaling (PRE1/BNQ1/bHLH136) or brassinosteroid signaling (ATBS1). Here we report that Arabidopsis lines over-expressing the PRE3/bHLH135/ATBS1/TMO7 gene are less responsive to red, far red and blue light than wild type which is likely to explain the light hyposensitive phenotype displayed when grown under white light conditions. Using qPCR, we show that the expression of PRE3 and KDR/PRE6 genes is regulated by light and that light-related genes are deregulated in the PRE3-ox lines. We show that PRE3 is expressed in the shoot and root meristems and that PRE3-ox lines also have a defect in lateral root development. Our results suggest that PRE3 is involved in the regulation of light signaling but also support the hypothesis that non-DNA binding bHLH genes are promiscuous genes regulating a wide range of both overlapping and specific regulatory pathways.

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