Abstract
Seed germination is the crucial stage in plant life cycle. Rapid and uniform germination plays an essential role in plant development and grain yield improvement. However, the molecular mechanism underlying seed germination speed is largely unknown due to the complexity of the dynamic process and the difficulty in phenotyping. Here, we conducted a time-series comparative transcriptome study of two elite maize inbred lines, 72-3 and F9721, with striking difference in seed germination speed, and identified a major locus underlying maize germination speed through genome-wide association analysis (GWAS) of an F2 segregation population. Comparative transcriptome study identified 12 h after imbibition (HAI) as the critical stage responsible for the variation in germination speed. The differentially expressed genes (DEGs) between 72-3 and F9721 were mainly enriched in metabolic pathways, biosynthesis of secondary metabolites, oxidoreductase activity pathways, hormone signal transduction, and amino acid transporter activity pathways. GWAS revealed that germination speed was controlled by a major locus on chromosome 1 with the leading SNP as AX-91332814, explaining 10.63% of phenotypic variation. A total of 87 proposed protein-coding genes surrounding the locus were integrated with DEGs. Combined with evidence from the gene expression database and gene synteny with other model species, we finally anchored three genes as the likely candidates regulating germination speed in maize. This study provides clues for the further exploration of genes controlling the maize seed germination speed, thus facilitating breeding of rapid germinated elite lines through marker assistant selection.
Highlights
Introduction iationsMaize (Zea mays L.) is a staple crop and primary resource for feed and biofuels
There was a stable increase in amylase activity in 72-3 after 6 h after imbibition (HAI) while the increase happened at 24 HAI in F9721, which seemed consistent with the rapid activation of starch degradation in endosperms
The results showed a consistent increase in differentially expressed genes (DEGs) with the progress of germinathe relatively less DEGs (321 genes) between 6 HAI and 0 HAI in both lines suggested a tion, and the relatively less DEGs (321 genes) between 6 HAI and 0 HAI in both lines similar biological status between early imbibing seeds and dry seeds
Summary
Introduction iationsMaize (Zea mays L.) is a staple crop and primary resource for feed and biofuels. Seed germination is an essential stage in the life cycle of higher plants [1]. The germinating seeds are highly vulnerable to biotic and abiotic factors including pathogen infection, extreme temperatures, drought, light, waterlogging, and salinity [2,3,4,5]. The frequent low temperature in the northern parts of China often causes collapsed seed germination, resulting in the high cost of planting and great loss in grain yield. Rapid and uniform seed germination is desired to avoid these damages, ensuring higher emergence rate and seedling vigor in the field. Seed germination is a complex process spanning sequential phases from seed recovering from maturation drying to metabolism resuming and cellular preparation for subsequent seedling growth. The dynamic process involves extensive physiological and Licensee MDPI, Basel, Switzerland
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