Simplifying the root dynamics: from complex hormone-environment interactions to specific root architectural modulation

The recent unveiling of the intriguing interactions among phytohormones and environmental cues in regulating root architecture for optimum plant acclimation has opened new avenues for research. Additional functions of transcriptional as well as protein-level regulators are being identified, uncovering novel interactions between hormonal and environmental signaling pathways, for shaping the root system architecture (RSA). Owing to the importance of root architectural dynamics under constantly encountered external factors, it is crucial to have a regular and comprehensive update of these interactions, affecting RSA, in order to improve crop performance. Moreover, it is equally important to identify and highlight, in crop species, the crucial regulators, which actively mediate hormonal as well as hormone-environment interactions, but have so far been characterized only in model plants such as Arabidopsis. Such updates will open up new research possibilities for plant biologists in extending the present knowledge on root system plasticity from Arabidopsis to economically important crop plants. Here, we provide a consolidated review of the recent findings on novel inter-hormonal and hormone-environment interactions with special emphasis on key downstream regulators and signaling pathways. We conclude by dissecting the gaps and challenges encountered at present, with an outline for future perspectives to channel the enormous information on hormone-environment regulation of RSA, towards a common output in the form of specific modulation of RSA components.