Expression of Mn-sod, PAL1, aos1 and HPL genes in soybean plants overexpressing the NmDef02 defensin.

Plant defensins are a potential tool in crop improvement programs through biotechnology. Their antifungal action makes them attractive molecules for the production of transgenic plants. Information is currently lacking on what happens to the expression of defense genes in transgenic plants that overexpress a defensin. Here we show the relative expression of four defense-related genes: Mn-sod, PAL1, aos1 and HPL evaluated in two transgenic soybean events (Def1 and Def17) constitutively expressing the NmDef02 defensin gene from Nicotiana megalosiphon. The expression of these defense genes showed a differential profile in the transgenic events, with the increased expression of the aos1 gene and the repression of the Mn-sod gene in both events, when compared to the non-transgenic control. Furthermore, the expression of the PAL1 gene only increased in the Def17 event. The results indicate that although there were some changes in the expression of defense genes in transgenic plants overexpressing the defensin NmDef02; the morphoagronomic parameters evaluated were similar to the non-transgenic control. Understanding the molecular changes that occur in these transgenic plants could be of interest in the short, medium and long term.

Field Resistance to Phakopsora pachyrhizi and Colletotrichum truncatum of Transgenic Soybean Expressing the NmDef02 Plant Defensin Gene.

Fungal diseases lead to significant losses in soybean yields and a decline in seed quality; such is the case of the Asian soybean rust and anthracnose caused by Phakopsora pachyrhizi and Colletotrichum truncatum, respectively. Currently, the development of transgenic plants carrying antifungal defensins offers an alternative for plant protection against pathogens. This paper shows the production of transgenic soybean plants expressing the NmDef02 defensin gene using the biolistic delivery system, in an attempt to improve resistance against diseases and reduce the need for chemicals. Transgenic lines were assessed in field conditions under the natural infections of P. pachyrhizi and C. truncatum. The constitutive expression of the NmDef02 gene in transgenic soybean plants was shown to enhance resistance against these important plant pathogens. The quantification of the P. pachyrhizi biomass in infected soybean leaves revealed significant differences between transgenic lines and the non-transgenic control. In certain transgenic lines there was a strong reduction of fungal biomass, revealing a less severe disease. Integration and expression of the transgenes were confirmed by PCR, Southern blot, and qRT-PCR, where the Def1 line showed a higher relative expression of defensin. It was also found that the expression of the NmDef02 defensin gene in plants of the Def1 line did not have a negative effect on the nodulation induced by Bradyrhizobium japonicum. These results indicate that transgenic soybean plants expressing the NmDef02 defensin gene have a substantially enhanced resistance to economically important diseases, providing a sound environmental approach for decreasing yield losses and lowering the burden of chemicals in agriculture.

Stress induced dynamic adjustment of conserved miR164:NAC module.

Aims including the rationale: Salinity and drought are the two major stresses limiting the productivity of economically important crops such as Glycine max (soybean). The incidence of these stresses during the pod development stages affects the quality and quantity of seeds, which compromise the yield of soybean. The miR164:NAC module has been shown to play a critical role in regulating the response to salt and drought stress in several plant species. However, biological role of miR164:NAC module in salt stress in soybean is not fully understood. Methods: In this study, we identified 215 salt responsive miRNAs, using miScript miRNA array with a sensitive and a tolerant soybean genotype, William82 and INCASoy36, respectively. The targets of these salt regulated miRNAs were searched in the degradome datasets. Key results: It was found that four salt stress deregulated miRNAs targeted the NAC transcription factor and among these miR164k and miR408d showed antagonistic expression in the two soybean genotypes. The expression of miR164k was higher in salt tolerant INCASoy36 as compared to salt sensitive William82, under unstressed conditions. However under salt stress, miR164k was downregulated in INCASoy36 (-2.65 fold), whereas it was upregulated in William82 (4.68 fold). A transient co-expression assay validated that gma-miR164k directs the cleavage of GmNAC1 transcript. Bioinformatics analysis revealed that the regulation of NAC transcription factor family by members of miR164 family is conserved across many species. The dynamic expression profiles of miR164 and NAC-TFs were captured in different tissues of rice, tobacco, and two soybean genotypes under drought and salt stress conditions. Main conclusion: Collectively, our results suggest that genetically determined dynamic modulation of the conserved miR164:NAC-TF module may play an important role in determining the adaptive response of plants to stress.