Plants are extremely flexible organisms adaptable to a range of diverse environments. Their intrinsic ability to simultaneously inhabit both above- and below-ground domains makes them unique among most other living organisms, which occupy a single habitat at a given time.

In response to diverse environmental signals, plants modify their development through the perception and integration of exogenous signals into the signalling pathways of plant hormones. Auxin is one of the most versatile plant hormones and plays essential roles in growth and development. The revelation of the existence of an auxin biosynthesis, signalling and transport apparatus in single-celled green algae is a clear indication that auxin has played an important evolutionary role during the adaptation of plants to diverse land environments.

In recent years, significant progress has been made towards understanding how this hormone regulates plant growth and development. However, less is known about the roles of auxin as a regulator of biotic and abiotic stress responses. In this free review article, interesting new insights into the role of auxin as an integrator of environmental signals are highlighted.

Kazan, K. (2013) Auxin and the integration of environmental signals into plant root development. Annals of botany, 112(9), 1655-1665

Background: Auxin is a versatile plant hormone with important roles in many essential physiological processes. In recent years, significant progress has been made towards understanding the roles of this hormone in plant growth and development. Recent evidence also points to a less well-known but equally important role for auxin as a mediator of environmental adaptation in plants.

Scope: This review briefly discusses recent findings on how plants utilize auxin signalling and transport to modify their root system architecture when responding to diverse biotic and abiotic rhizosphere signals, including macro- and micro-nutrient starvation, cold and water stress, soil acidity, pathogenic and beneficial microbes, nematodes and neighbouring plants. Stress-responsive transcription factors and microRNAs that modulate auxin- and environment-mediated root development are also briefly highlighted.

Conclusions: The auxin pathway constitutes an essential component of the plant’s biotic and abiotic stress tolerance mechanisms. Further understanding of the specific roles that auxin plays in environmental adaptation can ultimately lead to the development of crops better adapted to stressful environments.