The transcription factor SlNAP1 increases salt tolerance by modulating ion homeostasis and ROS metabolism in Solanum lycopersicum.

NAC transcription factors (TFs) play an important role in the plant resistant response to biotic and abiotic stresses. However, the functions of the most NAC TFs are still unknown, especially in tomato. Here, we identified and functionally characterized an NAC TFs, SlNAP1, in tomato, and found that SlNAP1 was significantly induced by salt stress. Under 150 mM NaCl treatments, morphological indexes of SlNAP1 over-expressed (SlNAP1-OE) transgenic tomato lines were significantly better than the wild-type (WT) plants. The content of Na+ in leaves and roots of SlNAP1-OE transgenic plants decreased, while the K+ content in leaves, roots, and stems increased compared with WT plants. The expression of the salt stress-related genes (NHX1, HKT1;2 and SOS1) in SlNAP1-OE plants were also significantly up-regulated under salt stress. The SOD, POD and CAT activities and the expression level of antioxidant oxidase synthesis genes of SlNAP1-OE lines were significantly increased. In addition, the SlNAP1-OE lines accumulated less MDA, H2O2 and O2•-, improved antioxidant defense systems which contributed to increase salt tolerance. In summary, our data suggest that SlNAP1 positively regulates salt tolerance in tomato by regulating ion homeostasis and ROS metabolism.

Dissection of Paenibacillus polymyxa NSY50-Induced Defense in Cucumber Roots against Fusarium oxysporum f. sp. cucumerinum by Target Metabolite Profiling.

To gain insights into the roles of beneficial PGPR in controlling soil-borne disease, we adopted a metabolomics approach to investigate the beneficial impacts of P. polymyxa NSY50 on cucumber seedling roots under the pathogen of Fusarium oxysporum f. sp. cucumerinum (FOC). We found that NSY50 pretreatment (NSY50 + FOC) obviously reduced the production of reactive oxygen species (ROS). Untargeted metabolomic analysis revealed that 106 metabolites responded to NSY50 and/or FOC inoculation. Under FOC stress, the contents of root osmotic adjustment substances, such as proline and betaine were significantly increased, and dehydroascorbic acid and oxidized glutathione (GSH) considerably accumulated. Furthermore, the contents of free amino acids such as tryptophan, phenylalanine, and glutamic acid were also significantly accumulated under FOC stress. Similarly, FOC stress adversely affected glycolysis and the tricarboxylic acid cycles and transferred to the pentose phosphate pathway. Conversely, NSY50 + FOC better promoted the accumulation of α-ketoglutaric acid, ribulose-5-phosphate, and 7-phosphosodiheptanone compared to FOC alone. Furthermore, NSY50 + FOC activated GSH metabolism and increased GSH synthesis and metabolism-related enzyme activity and their encoding gene expressions, which may have improved redox homoeostasis, energy flow, and defense ability. Our results provide a novel perspective to understanding the function of P. polymyxa NSY50, accelerating the application of this beneficial PGPR in sustainable agricultural practices.

Comparative Transcriptome Analysis and Genetic Methods Revealed the Biocontrol Mechanism of Paenibacilluspolymyxa NSY50 against Tomato Fusarium Wilt.

Fusarium wilt caused by Fusarium oxysporum f. sp. lycopersici (Fol) is a common disease that affects tomatoes, which can cause the whole plant to wilt and seriously reduce the production of tomatoes in greenhouses. In this study, the morphological indexes, photosynthetic performance and incidence rate of NSY50 under Fol infection were evaluated. It was found that NSY50 could improve the growth of tomato seedlings and significantly reduce the incidence rate of Fusarium wilt. However, the molecular mechanism of NSY50 that induces resistance to Fusarium wilt is still unclear. We used transcriptomic methods to analyze NSY50-induced resistance to Fol in tomatoes. The results showed that plant defense related genes, such as PR and PAL, were highly expressed in tomato seedlings pretreated with NSY50. At the same time, photosynthetic efficiency, sucrose metabolism, alkaloid biosynthesis and terpene biosynthesis were significantly improved, which played a positive role in reducing the damage caused by Fol infection and enhancing the disease tolerance of seedlings. Through transgenic validation, we identified an important tomato NAC transcription factor, SlNAP1, which was preliminarily confirmed to be effective in relieving the detrimental symptoms induced by Fol. Our findings reveal that P. polymyxa NSY50 is an effective plant-growth-promoting rhizosphere bacterium and also a biocontrol agent of soil-borne diseases, which can significantly improve the resistance of tomato to Fusarium wilt.