The Heterochronic Geneoryza Sativa Like Heterochromatin Protein 1modulates Mir156b/C/I/E Levels

The juvenile-to-adult transition in plants involves changes in vegetative growth and plant architecture; the timing of this transition has important implications for agriculture. The microRNA miR156 regulates this transition and shoot maturation in plants. InArabidopsis thaliana, deposition of histone H3 trimethylation on lysine 27 (H3K27me3, a repressive mark) at theMIR156A/Cloci is regulated by Polycomb Repressive Complex 1 (PRC1) or PRC2, depending on the developmental stage. The levels of miR156 progressively decline during shoot maturation. The amount of H3K27me3 atMIR156A/Cloci affects miR156 levels; however, whether this epigenetic regulation is conserved remains unclear. Here, we found that in rice (Oryza sativa), the putative PRC1 subunit LIKE HETEROCHROMATIN PROTEIN 1 (OsLHP1), with the miR156-SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) module, affects developmental phase transitions. Loss of OsLHP1 function results in ectopic expression ofMIR156B/C/I/E, phenocopy of miR156 overexpression, and reduced H3k27me3 levels atMIR156B/C/I/E. This indicates thatOsLHP1has functionally diverged fromArabidopsis LHP1. Genetic and transcriptome analyses of wild-type, miR156b/c-overexpression, andOslhp1-2mutant plants suggest that OsLHP1 acts upstream of miR156 and SPL during the juvenile-to-adult transition. Therefore, modifying the OsLHP1-miR156-SPL pathway may enable alteration of the vegetative period and plant architecture.