Loose Panicle1 encoding a novel WRKY transcription factor, regulates panicle development, stem elongation, and seed size in foxtail millet [Setaria italica (L.) P. Beauv.]

Abstract

Panicle development is an important agronomic trait that aids in determining crop productivity. Foxtail millet and its wild ancestor green foxtail have recently been used as model systems to dissect gene functions. Here, we characterized a recessive mutant of foxtail millet, loose-panicle 1 (lp1), which showed pleiotropic phenotypes, such as a lax primary branching pattern, aberrant branch morphology, semi-dwarfism, and enlarged seed size. The loose panicle phenotype was attributed to increased panicle lengths and decreased primary branch numbers. Map-based cloning, combined with high-throughput sequencing, revealed that LP1, which encodes a novel WRKY transcription factor, is responsible for the mutant phenotype. A phylogenetic analysis revealed that LP1 belongs to the Group I WRKY subfamily, which possesses two WRKY domains (WRKY I and II). A single G-to-A transition in the fifth intron of LP1 resulted in three disorganized splicing events in mutant plants. For each of these aberrant splice variants, the normal C2H2 motif in the WRKY II domain was completely disrupted, resulting in a loss-of-function mutation. LP1 mRNA was expressed in all of the tissues examined, with higher expression levels observed in inflorescences, roots, and seeds at the grain-filling stage. A subcellular localization analysis showed that LP1 predominantly accumulated in the nucleus, which confirmed its role as a transcriptional regulator. This study provides novel insights into the roles of WRKY proteins in regulating reproductive organ development in plants and may help to develop molecular markers associated with crop yields.

Development of a large population of activation‐tagged mutants in an elite indica rice variety

“…In rice, overexpression of glucosamine (N‐acetyl)‐6‐sulfatase ( GNS 4) gene which codes for a cytochrome P450 caused increased panicle length and grain size, suggesting its role in regulating both panicle and grain characters (Zhou et al, ). The loose‐panicle 1 ( LP1 ) gene, which codes for WRKY transcription factor, was highly expressed in young inflorescence and seeds compared to other tissues of foxtail millet, indicating its involvement in regulating panicle development (Xiang et al, ). An overview of these results amply suggests that some of these genes are upregulated by the enhancer element in the activation‐tagged mutants of rice.…”

SiSTL2 Is Required for Cell Cycle, Leaf Organ Development, Chloroplast Biogenesis, and Has Effects on C4 Photosynthesis in Setaria italica (L.) P. Beauv.

“…The raw sequencing data was deposited at EMBL-EBI in the European Nucleotide Archive database under the accession number ERP106777 . Data from the two sample pools were aligned to each other and analyzed in accordance with methods described in our previous study ( Xiang et al, 2017 ).…”

Domestication and Improvement in the Model C4 Grass, Setaria

“…Meanwhile, the use of bulked segregant analysis (BSA) to quickly analyze mutant collections generated by chemical mutagenesis ( Jiang et al, 2017 ) is accelerating Setaria gene discovery ( Xue et al, 2016 ; Fan et al, 2017 ; Huang et al, 2017 ). New genes contributing to leaf color ( Li et al, 2016 ), height, and inflorescence architecture ( Masumoto et al, 2016 ; Huang et al, 2017 ; Xiang et al, 2017 ; Yang et al, 2018 ) have been successfully identified with this approach, substantially advancing our understanding of important traits.…”