Regulatory Role of OsMADS34 in the Determination of Glumes Fate, Grain Yield, and Quality in Rice

Abstract

Grasses produce seeds on spikelets, a unique type of inflorescence. Despite the importance of grass crops for food, the genetic mechanisms that control spikelet development remain poorly understood. In this study, we used <i>m34-z</i>, a new mutant allele of the rice (<i>Oryza sativa</i>) E-class gene <i>OsMADS34</i>, to examine OsMADS34 function in determining the identities of glumes (rudimentary glume and sterile lemma) and grain size. In the <i>m34-z</i> mutant, both the rudimentary glume and sterile lemma were homeotically converted to the lemma-like organ and acquired the lemma identity, suggesting that OsMADS34 plays important roles in the development of glumes. In the <i>m34-z</i> mutant, most of the grains from the secondary panicle branches (spb) were decreased in size, compared with grains from wild-type, but no differences were observed in the grains from the primary panicle branches. The amylose content and gel consistency, and a seed-setting rate from the spb were reduced in the <i>m34-z</i> mutant. Interesting, transcriptional activity analysis revealed that OsMADS34 protein was a transcription repressor and it may influence grain yield by suppressing the expressions of <i>BG1</i>, <i>GW8</i>, <i>GW2</i>, and <i>GL7</i> in the <i>m34-z</i> mutant. These findings revealed that <i>OsMADS34</i> largely affects grain yield by affecting the size of grains from the secondary branches.