Mechanisms Of Meristem Maintenance By Maize Transcriptional Corepressors

The formation of the plant body proceeds in a sequential post-embryonic manner through the action of meristems. Tightly coordinated meristem regulation is required for development and reproductive success, eventually determining yield in crop species. In maize, the REL2 family of transcriptional corepressors includes four members, REL2, RELK1 (REL2-LIKE1), RELK2, and RELK3. In a screen for rel2 enhancers, we identified shorter double mutants with enlarged female inflorescence meristems (IMs) carrying mutations in RELK1 . Expression and genetic analysis indicate that REL2 and RELK1 cooperatively regulate female IM development by controlling genes involved in redox balance, hormone homeostasis, and differentiation, ultimately tipping the meristem toward an environment favorable to expanded expression of the ZmWUSCHEL1 gene, a key stem-cell promoting transcription factor. We further demonstrate that RELK genes have partially redundant yet diverse functions in the maintenance of various meristem types during development. By exploiting subtle increases in ear IM size in rel2 heterozygous plants, we also show that extra rows of kernels are formed across a diverse set of F1 hybrids. Our findings reveal that the REL2 family maintains development from embryonic initiation to reproductive growth and can potentially be harnessed for increasing seed yield in a major crop species. One sentence summary REL2-RELKs fine tune hormone and chemical cues to prevent expanded expression of ZmWUSCHEL1 in maize inflorescence meristems, and can potentially be harnessed for increasing seed yield in hybrids.