The Arabidopsis BRAHMA Chromatin Remodelling ATPase Is Involved in Direct Repression of Embryonic Traits in Leaves

Synthesis and accumulation of seed storage proteins (SSPs) is an important aspect of the seed maturation program. Genes encoding SSPs are specifically and highly expressed in the seed during maturation. However, the mechanisms that repress the expression of these genes in leaf tissue are not well understood. To gain insight into the repression mechanisms, we have performed a transgenic screening for mutants that express SSPs in leaves. Here we show that mutations of BRAHMA (BRM), a SNF2 chromatin remodelling ATPase, cause the ectopic expression of a subset of SSPs and other embryogenesis related genes in leaf tissue. Consistent with the notion that such SNF2-like ATPases form protein complexes in vivo, we observed similar phenotypes for mutations of AtSWI3C, a BRM interacting partner, and BSH, a SNF5 homolog and essential SWI/SNF subunit. Further, we present chromatin immunoprecipitation evidence that BRM is recruited to the promoters of a number of embryogenesis genes including the 2S genes, which are expressed/elevated in brm leaves. Consistent with its role in nucleosome remodelling, BRM appears to control the chromatin structure of the At2S2 promoter. These results show that a BRM-containing chromatin remodelling ATPase complex is involved in the direct repression of SSPs in leaf tissue.

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Tang X, Hou A, Babu M, Nguyen V, Hurtado L, Lu Q, Reyes JC, Wang A, Keller WA, Harada JJ, Tsang EW, Cui Y