Direct-seeded rice (DSR) cultivation is an effective and important way to resolve agricultural labor scarcity, water scarcity and high production cost issues. Mesocotyl elongation (ME) is the main driver of the rapid emergence of rice seedlings from the soil and is an important indicator of the suitability of rice varieties for direct seeding. Hence, discovering ME-related genes is particularly important for breeding rice varieties suitable for direct seeding. In this study, a chromosome segment substitution line (CSSL) population generated from a cross between Dongxiang common wild rice and Nipponbare (Nip) was used to map quantitative trait loci (QTLs) for ME. Two QTLs for mesocotyl length were identified on chromosomes 3 and 6 with logarithm of odds (LOD) scores ranging from 5.47 to 6.04 and explaining 15.95–16.79% of the phenotypic variance. Among these QTLs, qML6 accounted for the highest phenotypic variance (16.79%). Then, to confirm the strongest QTL, we generated an F2 segregating population via the CSL127 line harboring the qML6 locus and the recurrent parent Nip. The QTL qML6-1 associated with ME was mapped to a location between markers DX-C6-2 and DX-C6-4, which is consistent with the location of the previously mapped QTL qML6. qML6-1 had an LOD score of 8.45 and explained 30.56% of the phenotypic variance. The QTLs detected in this study provide promising targets for further genetic characterization and for use in marker-assisted selection to develop varieties with improved ME for the cultivation of DSR.
Background : The genus Brassica mainly comprises three diploid and three recently derived allotetraploid species, most of which are highly important vegetable, oil or ornamental crops cultivated worldwide. Despite being extensively studied, the origination of the allotetraploid crops and the overall phylogeny of Brassica genus are still far from completely resolved, which has greatly hindered the development of novel Brassica crops. Here, we target and integrate the chloroplast DNA and mitochondrial DNA to investigate the genetic diversity and relationships in large plant populations centering on Brassica genus. Results : The phylogenetic analyses based on a data set including 72 de novo assembled whole chloroplast genomes, delineated a comprehensive evolutional atlas inside and around Brassica genus. The maternal origin of both B. juncea and B. carinata are monophyletic from cam-type B. rapa and B. nigra , respectively. Nonetheless, the current B. napus contains three major cytoplasmic haplotypes: the cam -type which directly inherited from B. rapa , polima -type which is close to cam -type as a sister, and the predominant nap -type. Intriguingly, nap -type seems phylogenetically integrated with certain sparse C-genome wild species, thus implying that which may have primarily contributed the cytoplasm and the corresponding C subgenome to B. napus . Human breeding creation of the B. napus cytoplasmic male sterile lines (e.g., mori and nsa ) dramatically disturbed the concurrent inheritance between mtDNA and cpDNA. Strong parallel evolution among genera Raphanus , Sinapis, Eruca , Moricandia with Brassica indicates their uncomplete divergence from each other. Conclusions : The overall variation data and elaborated phylogenetic relationships obtained herein can substantially facilitate the development of novel Brassica crops, e.g. the allotetraploid rapeseed with new cytonuclear integrations and the allohexaploid rapeseed.
In this study, the regulatory effect of exogenous melatonin on the expression of genes related to the AsA-GSH cycle and nitrogen metabolism in seedlings under NaCl stress was determined; the homology between enzyme genes and similar genes in other species was analyzed by applying different concentrations of exogenous melatonin to rice seedlings under NaCl stress; and the morphology and physiological indicators of seedlings were determined. Exogenous melatonin was found to upregulate the expression of OsGR3, OsGPX1, OsNR2, OsGS1, and OsGOGAT1 in seedlings under NaCl stress, which enhanced the enzyme activities of the AsA-GSH cycle and nitrogen metabolism, ultimately reducing the content of reactive oxygen species (ROS) and improving the photosynthetic rate and nitrogen efficiency. A high homology was found when rice OsGR3, OsGPX1, OsNR2, OsGS1, and OsGOGAT1 were compared with similar genes in Arabidopsis thaliana, Hordeum vulgare, Zea mays, and Sorghum bicolor. Further, the location of the gene on the chromosome, the similar gene structure, GO annotation, and KEGG metabolic pathways were explained by the functions and metabolic processes of OsGR3, OsGPX1, OsNR2, OsGS1, and OsGOGAT1. Overall, our findings indicate that exogenous melatonin participates in the regulation of enzyme gene expression during the AsA-GSH cycle and nitrogen metabolism, ultimately affecting the activities of related enzymes and alleviating the oxidative damage induced by ROS in seedlings.
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