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Cadmium (Cd) is a widespread pollutant that is toxic to living organisms. Previous studies have identified certain WRKY transcription factors, which confer Cd tolerance in different plant species. In the present study, we have identified 29 Cd-responsive WRKY genes in Soybean [ Glycine max (L.) Merr.], and confirmed that 26 of those GmWRKY genes were up-regulated, while 3 were down-regulated. We have also cloned the novel, positively regulated GmWRKY142 gene from soybean and investigated its regulatory mechanism in Cd tolerance. GmWRKY142 was highly expressed in the root, drastically up-regulated by Cd, localized in the nucleus, and displayed transcriptional activity. The overexpression of GmWRKY142 in Arabidopsis thaliana and soybean hairy roots significantly enhanced Cd tolerance and lead to extensive transcriptional reprogramming of stress-responsive genes. ATCDT1 , GmCDT1-1 , and GmCDT1-2 encoding cadmium tolerance 1 were induced in overexpression lines. Further analysis showed that GmWRKY142 activated the transcription of ATCDT1 , GmCDT1-1 , and GmCDT1-2 by directly binding to the W-box element in their promoters. In addition, the functions of GmCDT1-1 and GmCDT1-2 , responsible for decreasing Cd uptake, were validated by heterologous expression in A. thaliana. Our combined results have determined GmWRKYs to be newly discovered participants in response to Cd stress, and have confirmed that GmWRKY142 directly targets ATCDT1 , GmCDT1-1 , and GmCDT1-2 to decrease Cd uptake and positively regulate Cd tolerance. The GmWRKY142-GmCDT1-1/2 cascade module provides a potential strategy to lower Cd accumulation in soybean. [ABSTRACT FROM AUTHOR]

The soybean mosaic virus (SMV) is a viral pathogen caused by Potyvirus reported in the major soybean growing areas of the world. SMV strain SC-15 is the most virulent and predominant strain that infects all soybean differentials and is widely distributed throughout southern China. In this study, three elite SMV-resistant soybean varieties that possess better comprehensive traits were identified through a screening test. A mapping population containing 163 F8 recombinant inbred lines derived from a Zhonghuang24 (resistant) × Huaxia3 (susceptible) cross was used to locate the resistance gene for SMV strain SC-15. A high-density genetic linkage map was developed containing 2639 recombination bins using the restriction site-associated DNA sequencing (RAD-seq) method. Results revealed a novel resistance gene, RSC15ZH identified in a 63 kb region of chromosome 13. This locus was further characterized by quantitative real-time PCR (qRT-PCR). Four candidate resistance genes were identified that were possibly involved in regulating SMV resistance, especially Glyma13g24461. These results provide a basic foundation for soybean breeding programs to improve resistance to SMV strain SC-15 and for positional cloning of SMV resistant candidate genes. [ABSTRACT FROM AUTHOR]

Aims: Aluminium (Al) stress is one of the most adverse abiotic factors limiting the growth and productivity of crops in acidic soils. Fine-mapping and cloning of quantitative trait loci (QTLs) provides an effective tool in analysing the genetic mechanisms underlying Al tolerance and in breeding Al-tolerant soybean varieties. Methods: Soybean cultivar Huachun2 in South China has been reported to be highly tolerant to multiple abiotic stresses in acidic soils, including Al stress. Here, we employ a recombinant inbred line (RIL) population derived from a cross of Huachun2 and Wayao to investigate the Al-tolerance QTLs. The prioritization method and qRT-PCR were applied to predict candidate genes in each QTL. Additionally, the functions of GmGSTU9 and GmPrx145 were investigated in transgenic soybean hairy roots. Results: In total, five QTLs associated with relative root elongation and Al content were identified by using the high-density genetic map in hydroponics. GmGSTU9, which encodes a glutathione S-transferase gene in qAl06, and GmPrx145, which encodes a class III peroxidase gene in qAl-HC2, were selected to further study the gene functions by using transgenic soybean hairy roots. In transgenic soybean hairy roots, the MDA, H2O2 and O2− contents in GmGSTU9- and GmPrx145-overexpressing hairy roots were lower than those in the control and RNA-interference-exposed hairy roots under Al stress. Conclusions: GmGSTU9 and GmPrx145 detected in qAl06 and qAl-HC2, respectively, positively regulate Al tolerance in soybean hairy roots by improving the antioxidant activity. These Al tolerance genes and molecular markers will be useful for marker-assisted selection to improve the Al tolerance of soybeans in acidic soils. [ABSTRACT FROM AUTHOR]

Key message: The Mendelian locus conferring resistance to powdery mildew in soybean was precisely mapped using a combination of phenotypic screening, genetic analyses, and high-throughput genome-wide sequencing. Powdery mildew (PMD), caused by the fungus Microsphaera diffusa Cooke & Peck, leads to considerable yield losses in soybean [Glycine max (L.) Merr.] under favourable environmental conditions and can be controlled by identifying germplasm resources with resistance genes. In this study, resistance to M. diffusa among resistant varieties B3, Fudou234, and B13 is mapped as a single Mendelian locus using three mapping populations derived from crossing susceptible with resistant cultivars. The position of the PMD resistance locus in B3 is located between simple sequence repeat (SSR) markers GMES6959 and Satt_393 on chromosome 16, at genetic distances of 7.1 cM and 4.6 cM, respectively. To more finely map the PMD resistance gene, a high-density genetic map was constructed using 248 F8 recombinant inbred lines derived from a cross of Guizao1 × B13. The final map includes 3748 bins and is 3031.9 cM in length, with an average distance of 0.81 cM between adjacent markers. This genotypic analysis resulted in the precise delineation of the B13 PMD resistance locus to a 188.06-kb genomic region on chromosome 16 that harbours 28 genes, including 17 disease resistance (R)-like genes in the reference Williams 82 genome. Quantitative real-time PCR assays of possible candidate genes revealed differences in the expression levels of 9 R-like genes between the resistant and susceptible parents. These results provide useful information for marker-assisted breeding and gene cloning for PMD resistance. [ABSTRACT FROM AUTHOR]