Student NATIONAL INSTITUTE OF PLANT GENOME RESEARCH NEW DELHI, Delhi, India
Body of Abstract: Mediator complex is a gigantic multiprotein complex that facilitates transcriptional regulation of eukaryotic gene expression. Structure of the whole complex seems to be stabilized by MED14, which acts as a backbone for the complex This study explains the role of MED14 in the transcriptional regulation of root system architecture in Arabidopsis. The root system is fragile in nature and its growth is dependent on cell division followed by cell elongation. We have found that the reduction in the level of AtMED14 affects primary root growth, but there are increase in the lateral root elongation and root hair formation. The transcriptomic analysis of med14 roots revealed the downregulation of flavonoid biosynthesis genes leading to deficiency of flavonoids. Increased lateral root emergence and the bushiness indicates the phosphate deficiency and causes iron toxicity in the root apical meristem of med14 mutants. Increased iron toxicity induces ROS accumulation, which poses a notable threat that may eventually lead to DNA damage. Excess ROS in the root epidermal cells of med14 also causes increased number of root hairs and also alteration in the primary root growth. Due to iron toxicity reduces the expression of the transporters to balance the iron equilibrium in the med14 mutant roots. In addition, MED14 was also found to regulate the DNA damage response (DDR) at the root meristem zone. Thus, this study unveils the importance of MED14 to regulate cell division and cell proliferation by balancing the ROS homeostasis in response to iron toxicity in the root apical meristem of Arabidopsis.