Overexpression of Taetr1-1 promotes enhanced seed dormancy and ethylene insensitivity in wheat.

MAIN CONCLUSION: Taetr1-1 can promote enhanced seed dormancy and ethylene insensitivity in wheat, indicating a conserved function of ETR1 in regulating seed dormancy. Lots of wheat cultivars have weak dormant seed. Weak seed dormancy can cause pre-harvest sprouting (PHS) in grain which significantly reduces grain yield and quality. The mining of causal genes of PHS resistance will serve to enhance breeding selection and cultivar development. In a previous study in Arabidopsis, we identified reduced dormancy 3 as a loss-of-function mutant of the ethylene receptor 1 (ETR1), which can control seed dormancy through the ERF12-TPL-DOG1 pathway. However, it is unknown whether ETR1 also functions in the regulation of wheat seed dormancy. To identify the regulatory role of ETR1 in wheat, we cloned TaETR1 and overexpressed the gain-of-function mutant Taetr1-1. The result indicated that overexpression of Taetr1-1 can promote enhanced seed dormancy and ethylene insensitivity in wheat. This study contributed to our understanding of the molecular basis for the regulation of wheat PHS resistance.

Combining QTL mapping and gene co-expression network analysis for prediction of candidate genes and molecular network related to yield in wheat.

BACKGROUND: Wheat (Triticum aestivum L.) is an important cereal crop. Increasing grain yield for wheat is always a priority. Due to the complex genome of hexaploid wheat with 21 chromosomes, it is difficult to identify underlying genes by traditional genetic approach. The combination of genetics and omics analysis has displayed the powerful capability to identify candidate genes for major quantitative trait loci (QTLs), but such studies have rarely been carried out in wheat. In this study, candidate genes related to yield were predicted by a combined use of linkage mapping and weighted gene co-expression network analysis (WGCNA) in a recombinant inbred line population. RESULTS: QTL mapping was performed for plant height (PH), spike length (SL) and seed traits. A total of 68 QTLs were identified for them, among which, 12 QTLs were stably identified across different environments. Using RNA sequencing, we scanned the 99,168 genes expression patterns of the whole spike for the recombinant inbred line population. By the combined use of QTL mapping and WGCNA, 29, 47, 20, 26, 54, 46 and 22 candidate genes were predicted for PH, SL, kernel length (KL), kernel width, thousand kernel weight, seed dormancy, and seed vigor, respectively. Candidate genes for different traits had distinct preferences. The known PH regulation genes Rht-B and Rht-D, and the known seed dormancy regulation genes TaMFT can be selected as candidate gene. Moreover, further experiment revealed that there was a SL regulatory QTL located in an interval of about 7 Mbp on chromosome 7A, named TaSL1, which also involved in the regulation of KL. CONCLUSIONS: A combination of QTL mapping and WGCNA was applied to predicted wheat candidate genes for PH, SL and seed traits. This strategy will facilitate the identification of candidate genes for related QTLs in wheat. In addition, the QTL TaSL1 that had multi-effect regulation of KL and SL was identified, which can be used for wheat improvement. These results provided valuable molecular marker and gene information for fine mapping and cloning of the yield-related trait loci in the future.

Genome-wide association study reveals a NAC transcription factor TaNAC074 linked to pre-harvest sprouting tolerance in wheat.

KEY MESSAGE: Twelve QTL associated with pre-harvest sprouting tolerance were identified using association analysis in wheat. Two markers were validated and a candidate gene TaNAC074 for Qgpf.cas-3B.2 was verified using Agrobacterium-mediated transformation. Pre-harvest sprouting (PHS) is a considerable global threat to wheat yield and quality. Due to this threat, breeders must identify quantitative trait loci (QTL) and genes conferring PHS-tolerance (PHST) to reduce the negative effects of PHS caused by low seed dormancy. In this study, we evaluated a panel of 302 diverse wheat genotypes for PHST in four environments and genotyped the panel with a high-density wheat 660 K SNP array. By using a genome-wide association study (GWAS), we identified 12 stable loci significantly associated with PHST (P < 0.0001), explaining 3.34 - 9.88% of the phenotypic variances. Seven of these loci co-located with QTL and genes reported previously. Five loci (Qgpf.cas-3B.2, Qgpf.cas-3B.3, Qgpf.cas-3B.4, Qgpf.cas-7B.2, and Qgpf.cas-7B.3), located in genomic regions with no known PHST QTL or genes, are likely to be new QTL conferring PHST. Additionally, two molecular markers were developed for Qgpf.cas-3A and Qgpf.cas-7B.3, and validated using a different set of 233 wheat accessions. Finally, the PHST-related function of candidate gene TaNAC074 for Qgpf.cas-3B.2 was confirmed by CAPS (cleaved amplified polymorphic sequences) marker association analysis in 233 wheat accessions and by expression and phenotypic analysis of transgenic wheat. Overexpression of TaNAC074 significantly reduced seed dormancy in wheat. This study contributes to broaden the genetic basis and molecular marker-assisted breeding of PHST.