Biology subjects

Kahlon, P. S.

Publications and source records attributed to Kahlon, P. S..

5 recordsLinked to original sources

bioRxiv2024

Quantitative light element (sodium and potassium) profiling in plant tissues using monochromatic X-ray fluorescence analysis

Accurately determining the elemental composition of plant tissues is essential for physiological studies on plant stress, including salinity tolerance. However, high-throughput routine analysis of light elements (range of sodium to calcium) in plant samples is challenging due to the need for complete sample dissolution and expensive inductively coupled plasma-mass-spectrometry (ICP-MS) analysis. Lower costs method (ion chromatography, ion selective electrodes) exists, but also require sample dissolution and lack sensitivity for very small samples (<10 mg). This study reports on a new method for the quantitative analysis of light elements in plant tissues using monochromatic X-ray fluorescence (XRF) instrumentation and innovative sample preparation and mounting. We used this approach to assess elemental uptake, distribution, and accumulation in Arabidopsis thaliana and Oryza sativa plants subjected to salt stress. The method can be used on samples as small as 1 mg making it suitable for small Arabidopsis thaliana plants. We systematically evaluated different sample preparations methods, repeatability, and measurement times to confirm the robustness of the technique. The results show that the monochromatic XRF method delivers rapid, non-destructive, and extraction-free analysis, strongly correlating with ICP-MS acquired data. As such, the monochromatic XRF method is a reliable and efficient alternative for studying salinity tolerance ideally suited for investigating elemental composition of early plant developmental stages, offering new possibilities for research into early stimuli sensing, perception and nutrient efficiency.

plant biology↗

bioRxiv2024

Cross-family transfer of the Arabidopsis cell-surface immune receptor LORE to tomato confers sensing of 3-hydroxylated fatty acids and enhanced disease resistance

Plant pathogens pose a high risk of yield losses and threaten food security. Technological and scientific advances have improved our understanding of the molecular processes underlying host-pathogen interactions, which paves the way for new strategies in crop disease management beyond the limits of conventional breeding. Cross-family transfer of immune receptor genes is one such strategy that takes advantage of common plant immune signaling pathways to improve disease resistance in crops. Sensing of microbe- or host damage-associated molecular patterns (MAMPs/DAMPs) by plasma membrane-resident pattern recognition receptors (PRR) activates pattern-triggered immunity (PTI) and restricts the spread of a broad spectrum of pathogens in the host plant. In the model plant Arabidopsis thaliana, the S-domain receptor-like kinase LIPOOLIGOSACCHARIDE-SPECIFIC REDUCED ELICITATION (AtLORE, SD1-29) functions as PRR, which senses medium chain-length 3-hydroxylated fatty acids (mc-3-OH-FAs), such as 3-OH-C10:0, and 3-hydroxyalkanoates (HAAs) of microbial origin to activate PTI. In this study, we show that ectopic expression of the Brassicaceae-specific PRR AtLORE in the solanaceous crop species Solanum lycopersicum cv. M82 leads to the gain of 3-OH-C10:0 immune sensing without altering plant development. AtLORE-transgenic tomato shows enhanced resistance against Pseudomonas syringae pv. tomato DC3000 and Alternaria solani NL03003. Applying 3-OH-C10:0 to the soil before infection induces resistance against the oomycete pathogen Phytophthora infestans Pi100 and further enhances resistance to A. solani NL03003. Our study proposes a potential application of AtLORE-transgenic crop plants and mc-3-OH-FAs as resistance-inducing bio-stimulants in disease management.

plant biology↗

bioRxiv2024

Bioengineering secreted proteases converts divergent Rcr3 orthologs and paralogs into extracellular immune co-receptors

Secreted immune proteases Rcr3 and Pip1 of tomato are both inhibited by Avr2 from the fungal plant pathogen Cladosporium fulvum but only Rcr3 act as a decoy co-receptor that detects Avr2 in the presence of the Cf-2 immune receptor. Here, we identified crucial residues from tomato Rcr3 required for Cf-2-mediated signalling and bioengineered various proteases to trigger Avr2/Cf-2 dependent immunity. Despite substantial divergences in Rcr3 orthologs from eggplant and tobacco, only minimal alterations were sufficient to trigger Avr2/Cf-2-triggered immune signalling. Tomato Pip1, by contrast, was bioengineered with 16 Rcr3-specific residues to initiate Avr2/Cf-2-triggered immune signalling. These residues cluster on one side next to the substrate binding groove, indicating a potential Cf-2 interaction site. Our findings also revealed that Rcr3 and Pip1 have distinct substrate preferences determined by two variant residues and that both are suboptimal for binding Avr2. This study advances our understanding of Avr2 perception and opens avenues to bioengineer proteases to broaden pathogen recognition in other crops.

plant biology↗

bioRxiv2021

Intraspecific diversity observed in the wild tomato species Solanum chilense in initial immune responses towards a glucan elicitor.

Natural plant populations are polymorphic and show intraspecific variation in resistance properties against pathogens. The activation of the underlying defence responses can depend on variation in perception of pathogen-associated molecular patterns or elicitors. To dissect such variation, we evaluated the responses induced by laminarin, (a glucan, representing an elicitor from oomycetes) in the wild tomato species Solanum chilense and correlated this to observed infection frequencies of Phytophthora infestans. We measured reactive oxygen species burst and levels of diverse phytohormones upon elicitation in 83 plants originating from nine populations. We found high diversity in basal and elicitor-induced levels of each component. Further we generated linear models to explain the observed infection frequency of P. infestans. The effect of individual components differed dependent on the geographical origin of the plants. We found that the resistance in the southern coastal region, but not in the other regions is directly correlated to ethylene responses and confirmed this positive correlation using ethylene inhibition assays. Our findings reveal high diversity in the strength of defence responses within a species and the involvement of different components with a quantitatively different contribution of individual components to resistance in geographically separated populations of a wild plant species. HighlightLarge-scale screenings reveal geographically distinct intraspecific differences in the dominant physiological pathogen defence responses upon glucan elicitor treatment in a wild tomato species.

plant biology↗

bioRxiv2020

Population studies in the wild tomato species Solanum chilense reveal maintenance and loss of resistance at geographically distinct locations

Natural plant populations encounter strong pathogen pressure and defense-associated genes are known to be under different selection pressure dependent on the pressure by the pathogens. Here we use wild tomato Solanum chilense populations to investigate natural resistance against Cladosporium fulvum, a well-known pathogenic fungus of domesticated tomatoes. We show that populations of S. chilense differ in resistance against the pathogen. Next, we explored the underlying molecular processes in a species wide-context. Then, focusing on recognition of the two prominent avirulence factors secreted by C. fulvum (Avr4 and Avr9) in central and northern populations of S. chilense we observed high complexity in the cognate homologues of Cladosporium resistance (Hcr9) locus underlying the recognition of these effectors. Presence of canonical genomic regions coding for Cf-4 and Cf-9, two major dominant resistance genes in the Hcr9 locus recognizing Avr4 and Avr9, respectively, does not meet prediction from Avr response phenotypes. We find both genes in varying fractions of the plant populations and we show possible co-existence of two functionally active resistance genes, previously thought to be allelic. Additionally, we observed the complete local absence of recognition of additional Avr proteins of C. fulvum. In the southern populations we attribute this to changes in the coregulatory network. As a result of loss of pathogen pressure or adaptation to extreme climatic conditions. This may ultimately explain the observed pathogen susceptibility in the southern populations. This work puts major gene mediated disease resistance in an ecological context.

ecology↗