Abscisic acid inhibits hypocotyl elongation acting on gibberellins, DELLA proteins and auxin

Hypocotyl elongation of Arabidopsis seedlings is influenced by light and numerous growth factors. Light inhibits hypocotyl elongation (photomorphogenesis), whereas elongation is promoted in the dark (skotomorphogenesis). Abscisic acid (ABA) plays a major role in these processes, but the molecular mechanism remains unclear.

ABA function in inhibition of hypocotyl elongation
Schematic model of ABA function in the inhibition of hypocotyl elongation in a DELLA-dependent or -independent pathway; ABA represses GA biosynthesis, thus DELLA proteins are stabilised, and inhibit the activity of PIFs, ultimately repressing auxin biosynthesis (left). Alternatively, ABA inhibits PIF proteins, which no longer induce both GA and auxin biosynthesis (right). Image credit: Lorrai et al.

In a recent Short Communication article in AoBP, Lorrai et al. provide a molecular framework for the effect of ABA on hypocotyl elongation in Arabidopsis seedlings, independently of light conditions. Their results show that ABA negatively controls hypocotyl elongation by acting on gibberellin metabolic genes, increasing the amount of the DELLA proteins, thus affecting GA signalling, and (ultimately) repressing auxin biosynthetic genes. This study paves the way to further work verifying this novel pathway that allows ABA to control cell expansion by acting on auxin synthesis.

Researcher highlight

Paola Vittorioso

Paola Vittorioso obtained a Master’s degree and PhD at Sapienza University of Rome, under the supervision of Prof. G. Macino. She was a post-doc at INRA-Versailles in the laboratories of M. Caboche between 1994 – 1997. Since 1997 she has been working at the Department of Biology and Biotechnology, Sapienza University of Rome, in collaboration with Prof. P. Costantino. Since 1999, she has been engaged as a researcher in the same department, where she is currently Assistant Professor. She is also a Review Editor for Frontiers in Plant Science.

Paola is a plant molecular geneticist, interested in light-mediated developmental processes, including seed germination and photomorphogenesis. She is particularly interested in the regulatory involvement of the ArabidopsisDof transcription factors DAG1 and DAG2 in these processes.


Reference List

Lorrai, R., Boccaccini, A., Ruta, V., Possenti, M., Costantino, P., & Paola, V. (2018). ABA inhibits hypocotyl elongation acting on gibberellins, DELLA proteins and auxin. AoB PLANTS. https://doi.org/10.1093/aobpla/ply061