RNA polymerase common subunit ZmRPABC5b is transcriptionally activated by Opaque2 and essential for endosperm development in maize

Abstract

Maize (Zea mays) kernel size is an important factor determining grain yield; although numerous genes regulate kernel development, the roles of RNA polymerases in this process are largely unclear. Here, we characterized the defective kernel 701 (dek701) mutant that displays delayed endosperm development but normal vegetative growth and flowering transition, compared to its wild type. We cloned Dek701, which encoded ZmRPABC5b, a common subunit to RNA polymerases I, II and III. Loss-of-function mutation of Dek701 impaired the function of all three RNA polymerases and altered the transcription of genes related to RNA biosynthesis, phytohormone response and starch accumulation. Consistent with this observation, loss-of-function mutation of Dek701 affected cell proliferation and phytohormone homeostasis in maize endosperm. Dek701 was transcriptionally regulated in the endosperm by the transcription factor Opaque2 through binding to the GCN4 motif within the Dek701 promoter, which was subjected to strong artificial selection during maize domestication. Further investigation revealed that DEK701 interacts with the other common RNA polymerase subunit ZmRPABC2. The results of this study provide substantial insight into the Opaque2–ZmRPABC5b transcriptional regulatory network as a central hub for regulating endosperm development in maize.

Central Roles of ZmNAC128 and ZmNAC130 in Nutrient Uptake and Storage during Maize Grain Filling

“…O2, serving as a core TF in maize endosperm filling [ 14 , 15 , 16 , 17 ], can genetically or molecularly interact with ZmNAC128/ZmNAC130, or NKD1/NKD2 to effectively coordinate endosperm filling [ 26 , 31 ]. Recently, two genes downstream of O2, namely, the GRAS domain-containing protein ZmGRAS11 [ 32 ] and the RNA polymerase common subunit ZmRPABC5b [ 33 ], have been characterized to play essential roles in endosperm filling development. However, the regulatory mechanisms underlying nutrient entry into grains are poorly understood, despite advancements in our understanding of nutrient storage metabolism.…”