OsMED16, a tail subunit of Mediator complex, interacts with OsE2Fa to synergistically regulate rice leaf development and blast resistance.

Mediator, a universal eukaryotic coactivator, is a multiprotein complex to transduce information from the DNA-bound transcription factors to the RNA polymerase II transcriptional machinery. In this study, the biofunctions of a rice mediator subunit OsMED16 in leaf development and blast resistance were characterized. OsMED16 encodes a putative protein of 1170 amino acids, which is 393 bp shorted than the version in Rice Genome Annotation Project databases. Overexpression of OsMED16 plants exhibited wider leaves with larger and more numerous cells in lateral axis, and enhanced resistance to M. oryzae with hyperaccumulated salicylic acid. Further analysis revealed that OsMED16 interacts with OsE2Fa in nuclei, and the complex could directly regulate the transcriptional levels of several genes involved in cell cycle regulation and SA mediated blast resistance, such as OsCC52A1, OsCDKA1, OsCDKB2;2, OsICS1 and OsWRKY45. Altogether, this study proved that OsMED16 is a positive regulator of rice leaf development and blast resistance, and providing new insights into the crosstalk between cell cycle regulation and immunity.