Enhanced resistance to fungal and bacterial diseases in tomato and Arabidopsis expressing BSR2 from rice

Cytochrome P450 SmCYP78A7a positively functions in eggplant response to salt stress via forming a positive feedback loop with SmWRKY11

Accumulating salinity in soil critically affected growth, development, and yield in plant. However, the mechanisms of plant against salt stress largely remain unknown. Herein, we identified a gene named SmCYP78A7a, which encoded a cytochrome P450 monooxygenase and belonged to the CYP78A sub-family, and its transcript level was significantly up-regulated by salt stress and down-regulated by dehydration stress. SmCYP78A7a located in the endoplasmic reticulum. Silencing of SmCYP78A7a enhanced susceptibility of eggplant to salt stress, and significantly down-regulated the transcript levels of salt stress defense related genes SmGSTU10 and SmWRKY11 as well as increased hydrogen peroxide (H2O2) content and decreased catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) enzyme activities. In addition, SmCYP78A7a transient expression enhanced eggplant tolerance to salt stress. By chromatin immunoprecipitation PCR (ChIP-PCR), luciferase reporter assay, and electrophoretic mobility shift assay (EMSA), SmWRKY11 activated SmCYP78A7a expression by directly binding to the W-box 6-8 (W-box 6, W-box 7, and W-box 8) within SmCYP78A7a promoter to confer eggplant tolerance to salt stress. In summary, our finds reveal that SmCYP78A7a positively functions in eggplant response to salt stress via forming a positive feedback loop with SmWRKY11, and provide a new insight into regulatory mechanisms of eggplant to salt stress.

Enhanced Resistance to Fungal and Bacterial Diseases Due to Overexpression of BSR1, a Rice RLCK, in Sugarcane, Tomato, and Torenia

Sugarcane smut caused by Sporisorium scitamineum is one of the most devastating sugarcane diseases. Furthermore, Rhizoctonia solani causes severe diseases in various crops including rice, tomato, potato, sugar beet, tobacco, and torenia. However, effective disease-resistant genes against these pathogens have not been identified in target crops. Therefore, the transgenic approach can be used since conventional cross-breeding is not applicable. Herein, the overexpression of BROAD-SPECTRUM RESISTANCE 1 (BSR1), a rice receptor-like cytoplasmic kinase, was conducted in sugarcane, tomato and torenia. BSR1-overexpressing tomatoes exhibited resistance to the bacteria Pseudomonas syringae pv. tomato DC3000 and the fungus R. solani, whereas BSR1-overexpressing torenia showed resistance to R. solani in the growth room. Additionally, BSR1 overexpression conferred resistance to sugarcane smut in the greenhouse. These three BSR1-overexpressing crops exhibited normal growth and morphologies except in the case of exceedingly high levels of overexpression. These results indicate that BSR1 overexpression is a simple and effective tool for conferring broad-spectrum disease resistance to many crops.

Overexpression of Rice BSR2 Confers Disease Resistance and Induces Enlarged Flowers in Torenia fournieri Lind

Plant pathogens evade basal defense systems and attack different organs and tissues of plants. Genetic engineering of plants with genes that confer resistance against pathogens is very effective in pathogen control. Conventional breeding for disease resistance in ornamental crops is difficult and lagging relative to that in non-ornamental crops due to an inadequate number of disease-resistant genes. Therefore, genetic engineering of these plants with defense-conferring genes is a practical approach. We used rice BSR2 encoding CYP78A15 for developing transgenic Torenia fournieri Lind. lines. The overexpression of BSR2 conferred resistance against two devastating fungal pathogens, Rhizoctonia solani and Botrytis cinerea. In addition, BSR2 overexpression resulted in enlarged flowers with enlarged floral organs. Histological observation of the petal cells suggested that the enlargement in the floral organs could be due to the elongation and expansion of the cells. Therefore, the overexpression of BSR2 confers broad-spectrum disease resistance and induces the production of enlarged flowers simultaneously. Therefore, this could be an effective strategy for developing ornamental crops that are disease-resistant and economically more valuable.