A NAC-EXPANSIN module enhances maize kernel size by controlling nucellus elimination

Maize early endosperm development is initiated in coordination with elimination of maternal nucellar tissues. However, the underlying mechanisms are largely unknown. Here, we characterize a major quantitative trait locus for maize kernel size and weight that encodes an EXPANSIN gene, ZmEXPB15. The encoded β-expansin protein is expressed specifically in nucellus, and positively controls kernel size and weight by promoting nucellus elimination. We further show that two nucellus-enriched transcription factors (TFs), ZmNAC11 and ZmNAC29, activate ZmEXPB15 expression. Accordingly, these two TFs also promote kernel size and weight through nucellus elimination regulation, and genetic analyses support their interaction with ZmEXPB15. Importantly, hybrids derived from a ZmEXPB15 overexpression line have increased kernel weight, demonstrates its potential value in breeding. Together, we reveal a pathway modulating the cellular processes of maternal nucellus elimination and early endosperm development, and an approach to improve kernel weight

Data from: Morphological, cellular and molecular evidences of chromosome random elimination in vivo upon haploid induction in maize

The mechanism of maternal in vivo haploid induction is not fully understood. In this study, the young embryos were identified by morphology, cytology and simple sequence repeat (SSR) markers at different developmental stages in the cross HZ514 (sweet corn) × HZI1 (inducer). The results indicated that the low seed setting rate was determined by the inducer pollen during the process of fertilization. The mosaic endosperm kernels and the different percentages of aneuploidy, mixploidy, lagged chromosome, micronuclei, chromosomal bridge and ring chromosome were found in the cross; 7.37% of the haploid embryos carried chromosome segments from HZI1. About 1% twin seedlings resulted from the cross and were analyzed by cytology and SSR markers. Four pairs of twin seedlings had different chromosome numbers (2n = 20 and 2n = 10–20) and there were some chromosome fragments from HZI1. Aneuploidy, mixploidy and the abnormal chromosomes occurred in the in vivo haploid induction by HZI1, which is the cytological basis for haploid induction and indicates that the inducer's chromosomes are prone to be lost during mitotic and meiotic divisions. Morphological, cellular and molecular evidences reveal that complete or partial chromosome elimination from inducer HZI1 controls the maize in vivo haploid induction

A Mitochondrial Transcription Termination Factor, ZmSmk3, Is Required for nad1 Intron4 and nad4 Intron1 Splicing and Kernel Development in Maize

The expression systems of the mitochondrial genes are derived from their bacterial ancestors, but have evolved many new features in their eukaryotic hosts. Mitochondrial RNA splicing is a complex process regulated by families of nucleus-encoded RNA-binding proteins, few of which have been characterized in maize (Zea mays L.). Here, we identified the Zea mays small kernel 3 (Zmsmk3) candidate gene, which encodes a mitochondrial transcription termination factor (mTERF) containing two mTERF motifs, which is conserved in monocotyledon; and the target introns were also quite conserved during evolution between monocotyledons and dicotyledons. The mutations of Zmsmk3 led to arrested embryo and endosperm development, resulting in small kernels. A transcriptome of 12 days after pollination endosperm analysis revealed that the starch biosynthetic pathway and the zein gene family were down-regulated in the Zmsmk3 mutant kernels. ZmSMK3 is localized in mitochondria. The reduced expression of ZmSmk3 in the mutant resulted in the splicing deficiency of mitochondrial nad4 intron1 and nad1 intron4, causing a reduction in complex I assembly and activity, impairing mitochondria structure and activating the alternative respiratory pathway. So, the results suggest that ZmSMK3 is required for the splicing of nad4 intron 1 and nad1 intron 4, complex I assembly and kernel development in maize

Phenotype and cytology raw data for CPB paper

Phenotype and cytology raw data for the paper "Morphological, cellular and molecular evidences of chromosome random elimination in vivo upon haploid induction in maize"

the sequence of SSR markers

the sequence of SSR markers for polymorphism analysis in the manuscript and some markers were used for haploid genotype analysis

Fine mapping and candidate gene prediction of a pleiotropic quantitative trait locus for yield-related trait in Zea mays.

The yield of maize grain is a highly complex quantitative trait that is controlled by multiple quantitative trait loci (QTLs) with small effects, and is frequently influenced by multiple genetic and environmental factors. Thus, it is challenging to clone a QTL for grain yield in the maize genome. Previously, we identified a major QTL, qKNPR6, for kernel number per row (KNPR) across multiple environments, and developed two nearly isogenic lines, SL57-6 and Ye478, which differ only in the allelic constitution at the short segment harboring the QTL. Recently, qKNPR6 was re-evaluated in segregating populations derived from SL57-6×Ye478, and was narrowed down to a 2.8 cM interval, which explained 56.3% of the phenotypic variance of KNPR in 201 F(2∶3) families. The QTL simultaneously affected ear length, kernel weight and grain yield. Furthermore, a large F(2) population with more than 12,800 plants, 191 recombinant chromosomes and 10 overlapping recombinant lines placed qKNPR6 into a 0.91 cM interval corresponding to 198Kb of the B73 reference genome. In this region, six genes with expressed sequence tag (EST) evidence were annotated. The expression pattern and DNA diversity of the six genes were assayed in Ye478 and SL57-6. The possible candidate gene and the pathway involved in inflorescence development were discussed