Tell me more: roles of NPRs in plant immunity

Jasmonic acid (JA) and its derivatives (jasmonates, JAs) are phytohormones with essential roles in plant defense against pathogenesis and herbivorous arthropods. Both the up- and down-regulation of defense responses are dependent on signaling pathways mediated by JAs as well as other stress hormones (e.g. salicylic acid), generally those involving the transcriptional and post-transcriptional regulation of transcription factors via protein modification and epigenetic regulation. In addition to the typical model plant Arabidopsis (a dicotyledon), advances in genetics research have made rice a model monocot in which innovative pest control traits can be introduced and whose JA signaling pathway can be studied. In this review, we introduce the dynamic functions of JAs in plant defense strategy using defensive substances (e.g. indole alkaloids and terpenoid phytoalexins) and airborne signals (e.g. green leaf volatiles and volatile terpenes) in response to biotrophic and necrotrophic pathogens as well as above-ground and below-ground herbivores. We then discuss the important issue of how the mutualism of herbivorous arthropods with viruses or bacteria can cause cross-talk between JA and other phytohormones to counter the defense systems.

Jasmonates Induce Both Defense Responses and Communication in Monocotyledonous and Dicotyledonous Plants

Phytoparasitic nematodes use multiple tactics to influence phytohormone physiology and alter plant developmental programs to establish feeding sites.

https://biblio.ugent.be/publication/8602877/file/8629576.pdf

Phytoparasitic Nematode Control of Plant Hormone Pathways.

Gall-forming root-knot nematodes hijack key plant cellular functions to induce multinucleate and hypertrophied feeding cells.

Biotic stresses are a potential threat to global food security. The origin of new pathogens and insect races due to climatic andgenetic factors is a major challenge for plant breeders in breeding biotic stress resistant crops. Yield losses due to biotic stresses haveresulted in 800 million people underfed in the world. Reduced yield due to biotic stresses and increasing food demand put internationalfood security at risk as 70% more food will be required in 2050. This review describes and compares the conventional and moleculargenetics methods being used for breeding biotic stress resistant crops. In the past, classical breeding approaches like introduction,hybridization, composite crossing, multiline, and backcross breeding were utilized for this purpose. However, these methods wereslow, expensive, and hectic for developing resistance in crops. Furthermore, breakdown of resistance due to fast evolving pathogenscould not be coped with using these time consuming methods. Therefore, molecular genetics approaches like mutation, marker assistedselection (MAS), genomics, recombinant DNA technology, targeted induced local lesions in genome (TILLING), and virus inducedgene silencing (VIGS) were adapted by breeders to develop effective resistance in crop plants in a shorter time. TILLING, being anontransgenic method, is expected to become the most powerful tool for this purpose.

https://journals.tubitak.gov.tr/agriculture/issues/tar-15-39-4/tar-39-4-1-1406-176.pdf

Modernization in plant breeding approaches for improving biotic stress resistance in crop plants

In Arabidopsis, non-expressor of pathogenesis related genes-1, NPR1 has been shown to be a positive regulator of the salicylic acid controlled systemic acquired resistance pathway and modulates the cross talk between SA and JA signaling. Transgenic plants expressing AtNPR1 constitutively exhibited resistance against pathogens as well as herbivory. In the present study, tobacco transgenic plants expressing AtNPR1 were studied further for their response to infection by the sedentary endoparasitic root knot nematode, Meloidogyne incognita. Transgenic plants showed enhanced resistance against the root-knot nematode infection. Prominent differences in the shoot and root weights of wild type and transgenic plants were observed post-inoculation with M. incognita. This was associated with a decrease in the number of root galls and egg masses in transgenic plants compared to WT. The transgenic plants also showed constitutive and induced expression of some PR protein genes, when challenged with M. incognita.

/pdf/transgenic-tobacco-plants-constitutively-expressing-1vp8ni1nd0.pdf

Transgenic tobacco plants constitutively expressing Arabidopsis NPR1 show enhanced resistance to root-knot nematode, Meloidogyne incognita.

Combined stress has been seen as a major threat to world agriculture production. Maize is one of the leading cereal crops of the world due to its wide spectrum of growth conditions and is moderately sensitive to salt stress. A saline soil environment is a major factor that hinders its growth and overall yield and causes an increase in the concentration of micronutrients like boron, leading to excess over the requirement of the plant. Boron toxicity combined with salinity has been reported to be a serious threat to the yield and quality of maize. The response signatures of the maize plants to the combined effect of salinity and boron stress have not been studied well. We carried out an integrative systems-level analysis of the publicly available transcriptomic data generated on tolerant maize (Lluteño maize from the Atacama Desert, Chile) landrace under combined salt and boron stress. We identified significant biological processes that are differentially regulated in combined salt and boron stress in the leaves and roots of maize, respectively. Protein-protein interaction network analysis identified important roles of aldehyde dehydrogenase (ALDH), galactinol synthase 2 (GOLS2) proteins of leaf and proteolipid membrane potential regulator (pmpm4), metallothionein lea protein group 3 (mlg3), and cold regulated 410 (COR410) proteins of root in salt tolerance and regulating boron toxicity in maize. Identification of transcription factors coupled with regulatory network analysis using machine learning approach identified a few heat shock factors (HSFs) and NAC (NAM (no apical meristem, Petunia), ATAF1–2 (Arabidopsis thaliana activating factor), and CUC2 (cup-shaped cotyledon, Arabidopsis)) family transcription factors (TFs) to play crucial roles in salt tolerance, maintaining reactive oxygen species (ROS) levels and minimizing oxidative damage to the cells. These findings will provide new ways to design targeted functional validation experiments for developing multistress-resistant maize crops.

/pdf/identifying-signal-crosstalk-mechanism-in-maize-plants-ju00sopv.pdf

Identifying Signal-Crosstalk Mechanism in Maize Plants during Combined Salinity and Boron Stress Using Integrative Systems Biology Approaches

Time-Course Transcriptome Analysis Identifies Rewiring patterns of Transcriptional Regulatory Networks in Rice under Rhizoctonia solani infection.

Reduced crop productivity results from altered plant physiological processes caused by dysfunctional proteins due to environmental stressors. In this study, a novel DnaJ Type-I encoding gene, VaDJI having a zinc finger motif in its C-terminal domain was found to be induced early upon treatment with heat stress (within 5 min) in a heat tolerant genotype of Vigna aconitifolia RMO-40. VaDJI is induced by multiple stresses. In tobacco, ectopic expression of VaDJI reduced ABA sensitivity during seed germination and the early stages of seedling growth of transgenic tobacco plants. Concomitantly, it also improved the ability of transgenic tobacco plants to withstand drought stress by modulating the photosynthetic efficiency, with the transgenic plants having higher Fv/Fm ratios and reduced growth inhibition. Additionally, transgenic plants showed a reduced build-up of H2O2 and lower MDA levels and higher chlorophyll content during drought stress, which attenuated cell damage and reduced oxidative damage. An analysis using the qRT-PCR study demonstrated that VaDJI overexpression is associated with the expression of some ROS-detoxification-related genes and stress-marker genes that are often induced during drought stress responses. These findings suggest a hypothesis whereby VaDJI positively influences drought stress tolerance and ABA signalling in transgenic tobacco, and suggests that it is a potential gene for genetic improvement of drought and heat stress tolerance in crop plants.

/pdf/ectopic-expression-of-dnaj-type-i-protein-homolog-of-vigna-3e2fvj3h.pdf

Ectopic expression of DnaJ type-I protein homolog of Vigna aconitifolia (VaDJI) confers ABA insensitivity and multiple stress tolerance in transgenic tobacco plants

PB Kirti

Papers

Transgenic tobacco plants constitutively expressing Arabidopsis NPR1 show enhanced resistance to root-knot nematode, Meloidogyne incognita.

Identifying Signal-Crosstalk Mechanism in Maize Plants during Combined Salinity and Boron Stress Using Integrative Systems Biology Approaches

Time-Course Transcriptome Analysis Identifies Rewiring patterns of Transcriptional Regulatory Networks in Rice under Rhizoctonia solani infection.

Ectopic expression of DnaJ type-I protein homolog of Vigna aconitifolia (VaDJI) confers ABA insensitivity and multiple stress tolerance in transgenic tobacco plants