The Mediator subunit OsMED15a is a transcriptional co-regulator of seed size/weight–modulating genes in rice

Publication date: Available online 13 September 2019Source: Biochimica et Biophysica Acta (BBA) - Gene Regulatory MechanismsAuthor(s): Nidhi Dwivedi, Sourobh Maji, Mohd Waseem, Pallabi Thakur, Vinay Kumar, Swarup K. Parida, Jitendra K. ThakurAbstractAlthough several transcription factors (TFs) that regulate seed size/weight in plants are known, the molecular landscape regulating this important trait is unclear. Here, we report that a Mediator subunit, OsMED15a, links rice grain size/weight-regulating TFs to their target genes. Expression analysis and high-resolution quantitative trait loci (QTL) mapping suggested that OsMED15a is involved in rice seed development. OsMED15a has an N-terminal, three-helical KIX domain. Two of these helices, α1 and α3, and three amino acids, 76LRC78, within OsMED15a helix α3 were important for its interaction with several proteins, including interactions with the transactivation domains of two NAC-type TFs, OsNAC024 and OsNAC025. Moreover, OsMED15a, OsNAC024, and OsNAC025 all exhibited increased expression during seed development, and we identified several grain size/weight-associated SNPs in these genes in 509 low- and high-grain-weight rice genotypes. RNAi-mediated repression of OsMED15a expression down-regulated the expression of the grain size/weight regulating genes GW2, GW5 and DR11 and reduced grain length, weight, and yield. Of note, both OsNAC024 and OsNAC025 bound to the promoters of these three genes. We conclude that the transacti...

Source: Biochimica et Biophysica Acta (BBA) Gene Regulatory Mechanisms - September 13, 2019 Category: Genetics & Stem Cells Source Type: research