Mediator complex: an important regulator of root system architecture.

Mediator, a multiprotein complex, is an important component of the transcription machinery. In plants, the latest reports from our group and some other studies have established that Mediator functions as a signal processor that conveys transcriptional signals from transcription factors to RNA polymerase II. It has been found to be involved in different developmental and stress-adaptation conditions ranging from embryo, root, and shoot development to flowering and senescence and also in response to different biotic and abiotic stresses. In the last one decade, significant progress has been made in understanding the role of Mediator subunits in root development. They have been shown to transcriptionally regulate development of almost all the components of root system architecture - primary root, lateral root and root hair. Their role has also been appreciated in nutrient acquisition through root. In this review, we have discussed all the known functions of Mediator subunits during root development. We have also highlighted the role of Mediator as a nodal point for processing different hormone signaling that regulate root morphogenesis and growth.