Search Results (7)

Rice blast disease, caused by Magnaporthe oryzae (M. oryzae), is a significant threat to global rice production. Conventional methods for disease management face limitations, emphasizing the importance of sustainable alternatives. In this study, two rice cultivars with different blast resistant abilities, the susceptible variety CO39 and the resistant variety Pi4b, were used as materials to study the effects of Piriformospora indica (Pi) on the resistance to M. oryzae infection and rice growth. The in vitro tests revealed no direct antagonistic interaction between Pi and M. oryzae. However, the in vivo experiments showed that Pi promoted plant growth by increasing root and shoot length, chlorophyll content, and nitrogen uptake, particularly in CO39 during pathogen infection. Pi inoculation also significantly reduced disease severity, which was indicated by smaller lesion areas and shorter lesion lengths in both cultivars but a more pronounced effect in CO39. This occurred due to the decreasing levels of MDA and the modulating activity of antioxidant enzymes in Pi-inoculated rice plants. At the early stage of M. oryzae infection, the expression of the ethylene signaling gene OsEIN2 and the gibberellin biosynthesis gene OsGA20ox1 in Pi-inoculated CO39 decreased but significantly increased in both rice cultivars at the later stage. The reverse was found for the pathogenesis-related (PR) genes OsPR10 and OsPBZ1 and the blast-resistant genes OsBRG1, OsBRG2, and OsBRW1, suggesting early growth suppression for rice resilience to blast followed by a later shift back to growth. Meanwhile, Pi inoculation increased OsCesA9 expression in rice to strengthen cell walls and establish the primary defense barrier against M. oryzae and upregulated the expression of OsNPR1 without a significant difference in CO39 but downregulated it in Pi4b to activate PR genes to enhance plant resistance. In summary, these results underscore the potential of Pi as a sustainable biological control agent for rice blast disease, which is particularly beneficial for blast-susceptible rice cultivars. Full article

Gerbera (Gerbera hybrida) is a popular cut flower on the market, so extending its vase life (VL) is an important goal in the horticultural industry. The aim of this study was to improve the freshness of gerbera cut flowers through the optimal solution (OS) and to analyze its preservation mechanism. We used chitosan (COS), calcium chloride (CaCl₂), and citric acid (CA) as the main ingredients of the vase solution and determined the OS ratio of 104 mg/L of COS, 92 mg/L of CA, and 93 mg/L of CaCl₂ using the Box–Behnken design-response surface method (BBD-RSM). Gerbera preservation results showed that the VL of the OS was 14.5 days, which was significantly longer than that of flowers maintained in the Basic Vase Solution (BVS) and the Commercial Formulation (CF) and was highly consistent with the theoretical VL of 14.57 d. Transcriptome analysis indicated that the OS might extend VL by regulating phytohormone signaling pathways, such as cytokinin and salicylic acid signaling. The qRT-PCR analysis of key candidate genes supported these findings, with significant upregulation observed in genes related to cytokinin synthesis (e.g., GhIPT1 and GhIPT9), salicylic acid signaling related to pathogen defense (e.g., GhTGA1, GhTGA4, GhNPR1, and GhRBOHA), and plant wax synthesis and stress response (e.g., GhKCS5, GhCUT1, and GhKCS6). Further, transcriptome GO-enrichment and physiological analysis showed that the OS might extend VL of Gerbera cut flowers by scavenging reactive oxygen species, including by activating the expression of genes related to oxidoreductase activity and the activities of antioxidant-system-related enzymes catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), and superoxide dismutase (SOD), while decreasing the malondialdehyde (MDA) content. These results provide valuable insights into the mechanisms underlying the extended VL of gerbera cut flowers and offer a foundation for developing more effective preservation techniques. Full article

The bacteria pathogen Xanthomonas oryzae pv. oryzae (Xoo) infects rice and causes the severe disease of rice bacteria blight. As the central regulator of the salic acid (SA) signaling pathway, NPR1 is responsible for sensing SA and inducing the expression of pathogen-related (PR) genes in plants. Overexpression of OsNPR1 significantly increases rice resistance to Xoo. Although some downstream rice genes were found to be regulated by OsNPR1, how OsNPR1 affects the interaction of rice-Xoo and alters Xoo gene expression remains unknown. In this study, we challenged the wild-type and OsNPR1-OE rice materials with Xoo and performed dual RNA-seq analyses for the rice and Xoo genomes simultaneously. In Xoo-infected OsNPR1-OE plants, rice genes involved in cell wall biosynthesis and SA signaling pathways, as well as PR genes and nucleotide-binding site-leucine-rich repeat (NBS-LRR) genes, were significantly upregulated compared to rice variety TP309. On the other hand, Xoo genes involved in energy metabolism, oxidative phosphorylation, biosynthesis of primary and secondary metabolism, and transportation were repressed. Many virulence genes of Xoo, including genes encoding components of type III and other secretion systems, were downregulated by OsNPR1 overexpression. Our results suggest that OsNPR1 enhances rice resistance to Xoo by bidirectionally regulating gene expression in rice and Xoo. Full article

Plant growth-promoting endophytic microbes have drawn the attention of researchers owing to their ability to confer fitness benefits in many plant species. Here, we report agriculturally beneficial traits of rice-leaf-adapted endophytic Microbacterium testaceum. Our polyphasic taxonomic investigations revealed its identity as M. testaceum. The bacterium displayed typical endophytism in rice leaves, indicated by the green fluorescence of GFP-tagged M. testaceum in confocal laser scanning microscopy. Furthermore, the bacterium showed mineral solubilization and production of IAA, ammonia, and hydrolytic enzymes. Tobacco leaf infiltration assay confirmed its non-pathogenic nature on plants. The bacterium showed antifungal activity on Magnaporthe oryzae, as exemplified by secreted and volatile organic metabolome-mediated mycelial growth inhibition. GC-MS analysis of the volatilome of M. testaceum indicated the abundance of antimicrobial compounds. Bacterization of rice seedlings showed phenotypic traits of MAMP-triggered immunity (MTI), over-expression of OsNPR1 and OsCERK, and the consequent blast suppressive activity. Strikingly, M. testaceum induced the transcriptional tradeoff between physiological growth and host defense pathways as indicated by up- and downregulated DEGs. Coupled with its plant probiotic features and the defense elicitation activity, the present study paves the way for developing Microbacterium testaceum-mediated bioformulation for sustainably managing rice blast disease. Full article

The white-backed planthopper (WBPH) is a major pest of rice crops and causes severe loss of yield. We previously developed the WBPH-resistant rice cultivar “OxF3H” by overexpressing the OsF3H gene. Although there was a higher accumulation of the flavonoids kaempferol (Kr) and quercetin (Qu) as well as salicylic acid (SA) in OxF3H transgenic (OsF3H or Trans) plants compared to the wild type (WT), it is still unclear how OsF3H overexpression affects these WBPH resistant-related changes in gene expression in OxF3H plants. In this study, we analyze RNA-seq data from OxF3H and WT at several points (0 h, 3 h, 12 h, and 24 h) after WBPH infection to explain how overall changes in gene expression happen in these two cultivars. RT-qPCR further validated a number of the genes. Results revealed that the highest number of DEGs (4735) between the two genotypes was detected after 24 h of infection. Interestingly, it was found that several of the DEGs between the WT and OsF3H under control conditions were also differentially expressed in OsF3H in response to WBPH infestation. These results indicate that significant differences in gene expression between the “OxF3H” and “WT” exist as the infection time increases. Many of these DEGs were related to oxidoreductase activity, response to stress, salicylic acid biosynthesis, metabolic process, defense response to pathogen, cellular response to toxic substance, and regulation of hormone levels. Moreover, genes involved in salicylic acid (SA) and ethylene (Et) biosynthesis were upregulated in OxF3H plants, while jasmonic acid (JA), brassinosteroid (Br), and abscisic acid (ABA) signaling pathways were found downregulated in OxF3H plants during WBPH infestation. Interestingly, many DEGs related to pathogenesis, such as OsPR1, OsPR1b, OsNPR1, OsNPR3, and OsNPR5, were found to be significantly upregulated in OxF3H plants. Additionally, genes related to the MAPKs pathway and about 30 WRKY genes involved in different pathways were upregulated in OxF3H plants after WBPH infestation. This suggests that overexpression of the OxF3H gene leads to multiple transcriptomic changes and impacts plant hormones and pathogenic-related and secondary-metabolites-related genes, enhancing the plant’s resistance to WBPH infestation. Full article

Chromium (Cr) is an important environmental constraint effecting crop productivity. Spermine (SPM) is a polyamine compound regulating plant responses to abiotic stresses. However, SPM-mediated tolerance mechanisms against Cr stress are less commonly explored in plants. Thus, current research was conducted to explore the protective mechanisms of SPM (0.01 mM) against Cr (100 µM) toxicity in two rice cultivars, CY927 (sensitive) and YLY689 (tolerant) at the seedling stage. Our results revealed that, alone, Cr exposure significantly reduced seed germination, biomass and photosynthetic related parameters, caused nutrient and hormonal imbalance, desynchronized antioxidant enzymes, and triggered oxidative damage by over-accretion of reactive oxygen species (ROS), malondialdehyde (MDA) and electrolyte leakage in both rice varieties, with greater impairments in CY927 than YLY689. However, seed priming with SPM notably improved or reversed the above-mentioned parameters, especially in YLY689. Besides, SPM stimulated the stress-responsive genes of endogenous phytohormones, especially salicylic acid (SA), as confirmed by the pronounced transcript levels of SA-related genes (OsPR1, OsPR2 and OsNPR1). Our findings specified that SPM enhanced rice tolerance against Cr toxicity via decreasing accumulation of Cr and markers of oxidative damage (H₂O₂, O₂^•− and MDA), improving antioxidant defense enzymes, photosynthetic apparatus, nutrients and phytohormone balance. Full article

In grafted plants, the movement of long-distance signals from rootstocks can modulate the development and function of the scion. To understand the mechanisms by which tolerant rootstocks improve scion responses to osmotic stress (OS) conditions, mRNA transport of osmotic responsive genes (ORGs) was evaluated in a tomato/potato heterograft system. In this system, Solanum tuberosum was used as a rootstock and Solanum lycopersicum as a scion. We detected changes in the gene expression levels of 13 out of the 21 ORGs tested in the osmotically stressed plants; of these, only NPR1 transcripts were transported across the graft union under both normal and OS conditions. Importantly, OS increased the abundance of StNPR1 transcripts in the tomato scion. To examine mRNA mobility in transgrafted plants, StNPR1 and StDREB1 genes representing the mobile and non-mobile transcripts, respectively, were overexpressed in tobacco (Nicotiana tabacum). The evaluation of transgenic tobacco plants indicated that overexpression of these genes enhanced the growth and improved the physiological status of transgenic plants growing under OS conditions induced by NaCl, mannitol and polyethylene glycol (PEG). We also found that transgenic tobacco rootstocks increased the OS tolerance of the WT-scion. Indeed, WT scions on transgenic rootstocks had higher ORGs transcript levels than their counterparts on non-transgenic rootstocks. However, neither StNPR1 nor StDREB1 transcripts were transported from the transgenic rootstock to the wild-type (WT) tobacco scion, suggesting that other long-distance signals downstream these transgenes could have moved across the graft union leading to OS tolerance. Overall, our results signify the importance of StNPR1 and StDREB1 as two anticipated candidates for the development of stress-resilient crops through transgrafting technology. Full article