Sit down before fact like a little child, and be prepared to give up every preconceived notion, follow humbly wherever and to whatever abyss Nature leads or you shall learn nothing.

Thomas Henry Huxley

Research

Interests & Aims

My long-term goal is to develop a microbiome-informed agronomy taking into account the evolutionary and ecological complexity of plant-microbiota interactions in agricultural soils.

My interests include:

The rhizosphere effect and plant immune interactions with the microbiota in community assembly.
The symbiosis continuum of the root and soil microbiome: pathogens, commensals, and mutualists.
The microbial ecology of biogeochemical cycling (e.g., nitrogen and carbon).

Present Research

Sundaresan Lab | UC Davis

The Rice Microbiome

I am currently testing the specific modulation of the rice root immune system by bacterial isolates that were collected from different rice fields in California. The plant immune system can effectively recognize, respond, and limit the growth of many microbes. A major unresolved question is how the abundant commensals and mutualists observed in plant root microbiomes are accommodated in this context, and why the plant immune system does not mount a strong response against the microbiota even though they possess the epitopes by which pathogens are detected. Many commensals and mutualists evade detection by the immune system directly by modifying their epitopes or indirectly, by downregulating epitope biosynthesis or otherwise altering the cell wall composition. Despite strategies to evade surveillance at the plant cell surface, many beneficial microbes still likely trigger this first layer of the plant immune system.

Some bacteria that live inside plants have been reported to use type III secretions systems (T3SS), bacterial molecular syringes, to inject effector proteins into plants that dampen the immune response and accommodate the bacterium. Metagenome studies have also detected enrichment of T3SS genes in root microbiomes, but non-pathogenic T3SS in the root microbiome have not been directly studied. In one of my projects, I have been addressing the hypothesis that T3SS are used as a mechanism for commensal microbes to competitively colonize the plant, also addressing a correlate hypothesis that the downregulation of MTI caused by these effectors allows the plant to control the accommodation of additional commensal and beneficial microbes by fine tuning the immune response that would otherwise be overstimulated. I have developed a laboratory model and protocols to simultaneously study plant-microbe and microbe-microbe interactions which will help to elucidate the principles of rice microbiome assembly.

Past Research

Hirsch Lab | UCLA

The Root Nodule Microbiome

Synergy between non rhizobial microbes and the legume-rhizobia symbiosis.

Scientific Publications

Khatibi, S.M.H., Dimaano, N.G., VELIZ, E., Sundaresan, V., and Ali, J. (2024). Exploring and exploiting the rice phytobiome to tackle climate change challenges. Plant Comm 0. https://doi.org/10.1016/j.xplc.2024.101078.

Martínez-Hidalgo, P., Humm, E.A., Still, D.W., Shi, B., Pellegrini, M., de la Roca, G., VELIZ, E., Maymon, M., Bru, P., Huntemann, M., et al. (2022). Medicago root nodule microbiomes: insights into a complex ecosystem with potential candidates for plant growth promotion. Plant Soil 471, 507–526. https://doi.org/10.1007/s11104-021-05247-7.

Youseif, S.H., Abd El-Megeed, F.H., Mohamed, A.H., Ageez, A., VELIZ, E., and Martínez-Romero, E. (2021). Diverse Rhizobium strains isolated from root nodules of Trifolium alexandrinum in Egypt and symbiovars. Systematic and Applied Microbiology 44, 126156. https://doi.org/10.1016/j.syapm.2020.126156.

Edwards, J., Santos-Medellín, C., Nguyen, B., Kilmer, J., Liechty, Z., VELIZ, E., Ni, J., Phillips, G., and Sundaresan, V. (2019). Soil domestication by rice cultivation results in plant-soil feedback through shifts in soil microbiota. Genome Biology 20, 1–14. https://doi.org/10.1186/s13059-019-1825-x.

VELIZ, E.A., Martínez-Hidalgo, P., and Hirsch, A.M. (2017). Chitinase-producing bacteria and their role in biocontrol. AIMSMICRO 3, 689–705. https://doi.org/10.3934/microbiol.2017.3.689.