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Vega, B.

Publications and source records attributed to Vega, B..

3 recordsLinked to original sources
bioRxiv2024

Engineering the plant intracellular immune receptor Sr50 to restore recognition of the AvrSr50 escape mutant

Pathogen-driven plant diseases cause significant crop losses worldwide. The introgression of intracellular nucleotide-binding leucine-rich repeat receptor (NLR) genes into elite crop cultivars is a common strategy for disease control, yet pathogens rapidly evolve to evade NLR-mediated immunity. The NLR gene Sr50 protects wheat against stem rust, a devastating disease caused by the fungal pathogen Puccinia graminis f. sp. tritici (Pgt). However, mutations in AvrSr50 allowed Pgt to evade Sr50 recognition, leading to resistance breakdown. Advances in protein structure modeling can enable targeted NLR engineering to restore recognition of escaped effectors. Here, we combined iterative computational structural analyses and site-directed mutagenesis to engineer Sr50 recognition of AvrSr50QCMJC, a Pgt effector variant that evades wild-type Sr50 detection. Derived by molecular docking, our initial structural model identified the K711D substitution in Sr50, which partially restored AvrSr50QCMJC recognition. Enhancing Sr50K711D expression via strong promoters compensated for weak recognition and restored robust immune responses. Further structural refinements led to the generation of five double and two triple receptor mutants. These engineered mutants, absent in nature, showed robust dual recognition for AvrSr50 and AvrSr50QCMJC in both Nicotiana benthamiana and wheat protoplasts. Notably, the K711D substitution was essential and synergistic with the additional substitutions for AvrSr50QCMJC recognition, demonstrating protein epistasis. Furthermore, this single substitution altered AlphaFold 2 predictions, enabling accurate modeling of the Sr50K711D-AvrSr50 complex structure, consistent with our final structural hypothesis. Collectively, this study outlines a framework for NLR engineering to counteract pathogen adaptation and provides novel Sr50 variants with potential for stem rust resistance.

plant biology↗
bioRxiv2023

Characterizing the microbial metagenome of calcareous stromatolite formations in the San Felipe Creek in Anza Borrego Desert

Here we describe the metagenome composition, community functional annotation, and diversity of prokaryotic microbial species derived from calcareous stromatolite formations discovered in the dry stream bed of the open-canopy, ephemeral San Felipe Creek in the Anza Borrego Desert. In this environment, resident microbes must be able to adapt to the harsh conditions of extreme heat, high UV light, desiccation and fluctuating solubilization/precipitation and hydration/evaporation. Metagenomic analysis revealed a community capable of carrying out complete nitrogen fixation and assimilatory nitrate reduction, forming biofilms and quorum sensing, and potentially forming thick-walled akinetes as desiccation-resistant stages. Nitrogen cycling is likely to play a fundamental role in mediating both the structure of the stromatolite microbial community and the mineral precipitation/dissolution. The viruses present in the stromatolites, particularly Nodularia and Mycobacterium phages are also likely to impact community population dynamics and activity. Stromatolite community members possess different morphological and physiological strategies to cope with desiccation stress. Metagenomic signatures were found for scytonemin, carotenoids, synthesis of potential microsporine-like amino acids; genes involved in microalgal desiccation tolerance, including those encoding aquaporins, chaperones, antioxidants; and enzymes responsible for the synthesis of trehalose, sucrose, and polyamines. The stromatolite ecosystem provides a diverse array of microniches where different functional guilds can develop complex metabolite exchange with the substrate supporting their life in extreme conditions. Metagenome analyses revealed several genes that might enable a specialized and unique group of endolithic cyanobacteria including Chroococcidiopsis, Hyella, Myxosarcina, and Pleurocapsa to derive metals and important nutrients from rocks, being potentially destructive for the calcareous formations. Our study revealed environmental adaptations of freshwater microbial communities in desert stream stromatolites which may provide valuable insights into Precambrian paleoenvironments, which are little known.

genomics↗