Biology subjects

Bose, J.

Publications and source records attributed to Bose, J..

8 recordsLinked to original sources

bioRxiv2025

Dehydrating microhabitats increase mite activity and intensify ectoparasitism of Drosophila

Parasites interact with their host in variable environments that are often subject to water scarcity and dehydration. Drosophila fruit flies and associated ectoparasitic mites interact across a range of microhabitats, typically in decaying organic matter, such as fallen fruit and cactus tissue, that dries out and deteriorates over periods ranging from days to months. Here, we report that mite parasitism of Drosophila increases with exposure to increasingly dry conditions for two fly-mite systems (D. nigrospiracula-Macrocheles and D. melanogaster-Gamasodes). In D. melanogaster, artificial selection for behavioral resistance did not eliminate this effect, as previously selected lines remained relatively more resistant than non-selected controls even under dry conditions. Water balance assays confirmed that mites became dehydrated when held under dry conditions, which was also associated with increased mite activity. Exposure of D. melanogaster to mites dehydrated by exposure to low relative humidity increased parasitism, further supporting that mite infestation intensifies under dry conditions. The results indicate that ectoparasitism in this system is affected by the water content of the mites. The increased motivation of mites to parasitise flies under dry conditions may serve to replenish mite water stores and facilitate dispersal to more favorable microhabitats.

physiology↗

bioRxiv2024

Evolutionary history with chronic malnutrition enhances pathogen susceptibility at older ages

Juvenile malnutrition is a global public health concern that negatively impacts the development and maturation of the immune system, leading to increased susceptibility to infectious diseases. Such adverse effects on immunity might increase with ageing, worsening disease conditions later in life. Furthermore, malnutrition may persist across generations, imposing strong natural selection to survive the nutrient shortage. However, it is unclear how the evolutionary history of ancestral generations with chronic malnutrition could influence pathogen resistance and infection susceptibility, as well as their age-specific changes in extant generations. To address this, we used Drosophila melanogaster populations adapted against chronic juvenile malnutrition and exposed them to a bacterial pathogen, Providencia rettgeri, during their early and late adulthood. Surprisingly, we observed that in populations adapted to chronic malnutrition, young flies survived infection better by tolerating the infection, while control flies displayed higher infection susceptibility despite carrying a similar pathogen load. However, this pattern in post-infection survival is reversed with ageing. There was no change in pathogen resistance, but evolved flies succumbed more to infection than control flies regardless of the input infection doses. Our study thus revealed new evolutionary insights into the development of contrasting early vs late-life immune strategies and age-specific vulnerabilities to infection as a function of early-life malnutrition.

evolutionary biology↗

bioRxiv2023

Shifted levels of sleep and activity under darkness as mechanisms underlying ectoparasite resistance

Parasites harm host fitness and are pervasive agents of natural selection capable of driving the evolution of host resistance traits. Indeed, host resistance in natural populations typically shows ample genetic variation, which may be maintained when parasite resistance imposes fitness costs on the host in the absence of parasites. Previously we demonstrated significant evolutionary responses to artificial selection for increasing behavioral immunity to Gamasodes queenslandicus mites in replicate lines of Drosophila melanogaster. Here, we report transcriptional shifts in metabolic processes between selected and control fly lines based on RNA-seq analyses. We also show decreased starvation resistance and increased use of nutrient reserves in flies from mite-resistant lines. Additionally, resistant lines exhibited increased behavioral activity, reduced sleep, and elevated oxygen consumption under conditions of darkness. Using an independent panel of D. melanogaster genetic lines exhibiting variable sleep durations, we found a positive correlation between mite resistance and reduced sleep, providing additional support for a link between resistance and sleep. Experimentally restraining the activity of artificially selected mite-resistant flies during exposure to parasites under dark conditions reduced their resistance advantage relative to control flies. The results suggest that ectoparasite resistance in this system involves increased dark-condition activity and metabolic gene expression at the expense of nutrient reserves and starvation resistance. Significance statementParasites are potent agents of selection, yet resistance may often be constrained evolutionarily because of trade-offs involving other fitness-related traits. Using artificial selection, we show that resistance to ectoparasites directly increases metabolism and decreases starvation resistance, predominantly through altered sleep and activity patterns at night. These studies highlight that active-resting patterns of the host are a significant driving force in ectoparasite resistance, but may have a negative impact on fitness during periods of low food availability. Our strongly integrative work suggests that parasite pressure may influence the evolution of host sleep and activity patterns.

evolutionary biology↗

bioRxiv2022

Heritability and pre-adult survivorship costs of ectoparasite resistance in the naturally occurring Drosophila-Gamasodes mite system

Our understanding of the evolutionary significance of ectoparasites in natural communities is limited by a paucity of information concerning the mechanisms and heritability of resistance to this ubiquitous and diverse assemblage of organisms. Here, we report the results of artificial selection for increasing ectoparasite resistance in replicate lines of Drosophila melanogaster derived from a field-fresh population. Resistance, as ability to avoid infestation by naturally occurring Gamasodes queenslandicus mites, increased significantly in response to selection, and realized heritability (s.e.) was estimated to be 0.11 (0.0090). Ability to deploy energetically expensive bursts of flight from the substrate was a main mechanism of resistance that responded to selection, aligning with previously documented metabolic costs of fly behavioral defenses. Host body size, which affects parasitism rate in some fly-mite systems, was not shifted by selection. In contrast, resistant lines expressed significant reductions in larva-to-adult survivorship with increasing toxic (ammonia) stress, identifying an environmentally modulated pre-adult cost of resistance. Flies resistant to G. queenslandicus were also more resistant to a different mite, Macrocheles subbadius, suggesting that we documented genetic variation and a pleiotropic cost of broad-spectrum behavioral immunity against ectoparasites. This study demonstrates significant evolutionary potential of an ecologically important trait.

evolutionary biology↗

bioRxiv2022

The wheat multi-pathogen resistance gene, Lr67res, confers a novel gain-of-function phenotype involving anion fluxes

Partial resistance to multiple biotrophic fungal pathogens in wheat (Triticum aestivum L.) is conferred by the Lr67 gene, which encodes a Sugar Transport Protein 13 (STP13) family hexose-proton symporter variant. Two mutations (G144R, V387L) differentiate the resistant and susceptible protein variants (Lr67res and Lr67sus). The molecular function of the Lr67res protein is not well understood. We functionally characterized the wheat Lr67res protein variant using two heterologous expression systems - Xenopus laevis oocytes and Saccharomyces cerevisiae yeast. Wheat and barley (Hordeum vulgare) were used to verify disease resistance capability of Lr67/STP13 variants. The Lr67res allele, but not Lr67sus, induced large sugar-independent, anion-dominated currents in oocytes and an increased sensitivity to ions in yeast, implicating a novel gain-of-function. We demonstrate that the single mutant variant, Lr67susG144R, confers disease resistance in wheat and that transgenic barley (Hordeum vulgare L.) plants expressing the orthologous HvSTP13 gene carrying the equivalent mutations present in Lr67res exhibited increased resistance to Puccinia hordei. NaCl treatment was found to induce leaf tip necrosis in Lr67res wheat. An Lr67res-like gain-of-function can be introduced into orthologous plant hexose transporters via single amino acid mutation, highlighting the possibility of generating disease resistance in other crop species, especially with gene editing. One sentence summaryThe wheat Lr67res protein responsible for multipathogen resistance has a gain-of-function over the Lr67sus protein, that is associated with anion fluxes and likely contributes to disease resistance.

plant biology↗

bioRxiv2021

Zoom in on Ca2+ pattern and ion flux dynamics to decode spatial and temporal regulation of cotton fiber growth

Cotton fibers are single-celled trichomes initiated from ovule epidermis prior to anthesis. Thereafter, the fibers undergo rapid elongation for 20 d before switching to intensive cell wall cellulose synthesis. The final length attained determines fiber yield and quality. As such, cotton fiber represents an excellent single cell model to study regulation of cell growth and differentiation, with significant agronomical implications. One major unresolved question is whether fiber elongation follows a diffusive or a tip growth pattern. We addressed this issue by using cell biology and electrophysiological approaches. Confocal imaging of Ca2+ binding dye, fluo-3 acetoxymethyl (Fluo-3), and in situ microelectrode ion flux measurement revealed that cytosolic Ca2+ was evenly distributed along the elongating fiber cells with Ca2+ and H+ fluxes oscillating from apical to basal regions of the elongating fibers. These findings demonstrate that, contrary to growing pollen tubes or root hairs, cotton fiber growth follows a diffusive, but not the tip growth, pattern. Further analyses showed that the elongating fibers exhibited substantial net H+ efflux, indicating a strong activity of the plasma membrane H+-ATPase required for energy dependent solute uptake. Interestingly, the growing cotton fibers were responding to H2O2 treatment, know to promote fiber elongation, by a massive increase in the net Ca2+ and H+ efflux in both tip and basal zones, while non-growing cells lacked this ability. These observations suggest that desensitization of the cell and a loss of its ability to respond to H2O2 may be causally related to the termination of the cotton fiber elongation. One sentence summaryConfocal imaging of Ca2+ patterning and in situ microelectrode ion flux measurements demonstrate that, contrary to growing pollen tubes or root hairs, cotton fiber growth follows a diffusive, but not the tip growth, pattern.

cell biology↗

bioRxiv2020

A single nucleotide substitution in TaHKT1;5-D controls shoot Na+ accumulation in bread wheat

Improving salinity tolerance in the most widely cultivated cereal, bread wheat (Triticum aestivum L.), is essential to increase grain yields on saline agricultural lands. A Portuguese landrace, Mocho de Espiga Branca accumulates up to 6 folds greater leaf and sheath sodium (Na+) than two Australian cultivars, Gladius and Scout, under salt stress. Despite high leaf and sheath Na+ concentrations, Mocho de Espiga Branca maintained similar salinity tolerance compared to Gladius and Scout. A naturally occurring single nucleotide substitution was identified in the gene encoding a major Na+ transporter TaHKT1;5-D in Mocho de Espiga Branca, which resulted in a L190P amino acid residue variation. This variant prevents Mocho de Espiga Branca from retrieving Na+ from the root xylem leading to a high shoot Na+ concentration. The identification of the tissue tolerant Mocho de Espiga Branca will accelerate the development of more elite salt tolerant bread wheat cultivars.

plant biology↗

bioRxiv2020

GmSALT3 confers shoot Na+ and Cl- exclusion in soybean via two distinct processes.

Soybean (Glycine max) yields are threatened by multiple stresses including soil salinity. GmSALT3 confers net shoot exclusion for both Na+ and Cl- and improves salt tolerance of soybean; however, how the ER-localised GmSALT3 achieves this is unknown. Here, GmSALT3s function was investigated in heterologous systems and near-isogenic lines that contained the full-length GmSALT3 (NIL-T; salt-tolerant) or a truncated transcript Gmsalt3 (NIL-S; salt-sensitive). GmSALT3 restored growth of K+-uptake-defective E. coli and contributed toward net influx and accumulation of Na+, K+, and Cl- in Xenopus laevis oocytes, while Gmsalt3 was non-functional. A time-course analysis of the NILs confirmed that shoot Cl- exclusion breaks down prior to Na+ exclusion, while grafting showed that shoot Na+ exclusion occurs via a root xylem-based mechanism. In contrast, NIL-T plants exhibited significantly greater Cl- content in both the stem xylem and phloem sap compared to NIL-S, indicating that shoot Cl- exclusion likely depends upon novel phloem-based Cl- recirculation. NIL-T shoots grafted on NIL-S roots contained low shoot Cl-, which confirmed that Cl- recirculation is dependent on the presence of GmSALT3 in shoots. Overall, these findings provide new insights on GmSALT3s impact on salinity tolerance and reveal a novel mechanism for shoot Cl- exclusion in plants. HighlightGmSALT3 improves soybean salt tolerance. Here, using heterologous expression, we found GmSALT3 is a functional ion transporter, and, in planta that it confers shoot salt exclusion through root-based Na+ xylem exclusion and shoot-based Cl- exclusion via phloem derived Cl- recirculation.

plant biology↗