<i>NONSTOP GLUMES1</i> Encodes a C2H2 Zinc Finger Protein That Regulates Spikelet Development in Rice

Abstract

The spikelet is an inflorescence structure unique to grasses. The molecular mechanisms underlying spikelet development and evolution are unclear. In this study, we characterized three allelic recessive mutants in rice (<i>Oryza sativa</i>): <i>nonstop glumes 1-1</i> (<i>nsg1-1</i>), <i>nsg1-2</i>, and <i>nsg1-3</i> In these mutants, organs such as the rudimentary glume, sterile lemma, palea, lodicule, and filament were elongated and/or widened, or transformed into lemma- and/or marginal region of the palea-like organs. <i>NSG1</i> encoded a member of the C2H2 zinc finger protein family and was expressed mainly in the organ primordia of the spikelet. In the <i>nsg1-1</i> mutant spikelet, <i>LHS1 DL</i>, and <i>MFO1</i> were ectopically expressed in two or more organs, including the rudimentary glume, sterile lemma, palea, lodicule, and stamen, whereas <i>G1</i> was downregulated in the rudimentary glume and sterile lemma. Furthermore, the NSG1 protein was able to bind to regulatory regions of <i>LHS1</i> and then recruit the corepressor TOPLESS-RELATED PROTEIN to repress expression by downregulating histone acetylation levels of the chromatin. The results suggest that <i>NSG1</i> plays a pivotal role in maintaining organ identities in the spikelet by repressing the expression of <i>LHS1</i>, <i>DL</i>, and <i>MFO1.</i>