Characterization of the <i>NGP4A</i> Gene in Regulating Grain Number Per Panicle of Rice (<i>Oryza sativa</i> L.)
2022
Yanhong Chen | Wanling Yang | Minmin Zhao | Gumu Ding | Yi Zhou | Jiankun Xie | Fantao Zhang
Grain number per panicle (GNPP) is a major factor influencing rice yield (<i>Oryza sativa</i> L.). However, the molecular mechanisms of GNPP determination are not well understood. A rice GNPP mutant, <i>ngp4a,</i> was isolated from an ethyl methanesulfonate-mutagenized rice library of <i>japonica</i> Nipponbare. <i>ngp4a</i> produced fewer grains than wild-type plants at maturity as the number of secondary branches decreased significantly. The mutant phenotype of <i>ngp4a</i> was controlled by a recessive nuclear gene, which was fine-mapped into a 155.2 kb region on chromosome 4. One GNPP-related gene, <i>Gnp4</i>/<i>LAX2</i> (<i>LOC_Os04g32510</i>), was found in the mapped region. The deletion of 3-bp nucleotides in the first exon of <i>NGP4A</i> resulted in a threonine residue loss. The mutation in <i>NGP4A</i> was responsible for the mutant phenotype of <i>ngp4a</i>. These results suggest that <i>NGP4A</i> is a new allele for <i>Gnp4</i> and <i>LAX2</i>, while the mutant phenotype and underlying causation differed. Notably, transcriptome analysis revealed that <i>NGP4A</i> could regulate GNPP determination through the phenylpropanoid biosynthesis and mitogen-activated protein kinase signaling pathways. Our results further elucidated the vital roles of <i>Gnp4</i>/<i>LAX2</i> in GNPP determination, providing a new genetic resource and theoretical basis to further explore the molecular mechanisms of GNPP in rice.
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