(A) In wild type (WT), TSO1 and SOL2 function as essential components of two independent, yet functionally redundant, chromatin complexes. Yellow flashes indicate functional complexes. (B) In tso1-1/TSO1 heterozygous plants, TSO1, at half of the wild type amount, is sufficient to confer wild type phenotype even in the presence of tso1-1, which completely or partially disables SOL2. (C) In tso1-1/tso1-1 (class I) mutants, both TSO1 and SOL2 are nonfunctional due to an absence of wild type TSO1 and the inhibition of SOL2 by tso1-1. (D) In tso1 class II mutants, such as tso1-3 or tso1-5, SOL2 is functional and compensates for a lack of TSO1, leading to the development of normal flowers.