University of Missouri

ABOUT THE LAB

The main projects of the Mendoza lab are:

1. Iron sensing and crosstalk between iron and sulfur homeostatic networks.
   • Iron sensing and crosstalk between iron and sulfur homeostatic networks. If given enough water and light, plants can assimilate all the nutrients they need in elemental or inorganic forms (e.g. Fe2+, SO42-) and synthesize all the molecules required to complete their life cycle. Biochemically speaking, this is a feat that only few organisms on Earth can achieve. Plants, however, also need to regulate the uptake of nutrients to prevent an overload. This is particularly critical for reactive elements such as iron (Fe), which is essential for respiration, photosynthesis and other processes but in excess, promotes the formation of reactive oxygen species (ROS), which may damage proteins, membranes, and DNA. Sulfur metabolism in plants is tightly associated with Fe homeostasis; this is not surprising considering that iron-sulfur (Fe-S) clusters are at the core of respiratory and photosynthetic complexes. However, how these two pathways communicate with each other at the molecular level is unknown.
2. Regulation of nutrient uptake when plants sense the presence of pathogens.
   • Every organism on Earth requires Fe for their metabolism and plants have evolved remarkable strategies to mine the insoluble Fe from the Earth’s crust. In turn, plants are the main source of Fe for humans, livestock, and microbes living on leaves. This represents an additional challenge for plants as not only they have to secure enough Fe for their own metabolism, but they also need to prevent “feeding” organisms (pathogens) that could become potentially lethal to the plant. This crosstalk between biotic and abiotic stresses is relatively new and vastly understudied; therefore, in collaboration with Drs. Scott Peck and Antje Heese (MU Biochemistry), we began exploring how plants integrate information from a wide range of environmental stimuli to evoke the correct biological responses.
3. The role of the microbiota in governing nutrient accumulation in plants.
   • The role of the microbiota in governing nutrient accumulation in plants. Recent research has demonstrated that plant-microbiome interactions play important roles in Fe homeostasis since plants mine Fe from the soil and microorganisms living in plant tissues benefit from this Fe availability. In turn, plants have been shown to release Fe-chelating molecules to favor the colonization of beneficial or non-pathogenic microorganisms over pathogenic ones. The molecular basis of these interactions has remained elusive for years as many of the gene identification and function assignments have been done under sterile conditions. Plant-microbe interactions is an emerging field with plenty of opportunities to advance basic biology. Moreover, since some bacteria can perform geochemical transformations that plants cannot, this research may generate translatable knowledge to develop crops with better nutrient use efficiency.
4. Improving transport efficiency and selectivity by continuous evolution.
   • Synthetic biology is a relatively new field that has the potential to dramatically change the way we engineer biological systems. Directed, or continuous evolution, is a branch of synthetic biology where the approach is to explore design spaces that have not been explored by natural evolution. Moreover, it can do so in an extraordinarily short period of time as it mimics natural selection in a laboratory setting. There are many platforms to pursue directed evolution experiments, including in vitro and in vivo campaigns, but the core principle is the same: the introduction of random mutations into a target (e.g. RNA or DNA), followed by screening and selection for variants with the desired trait. From the different available platforms, we have selected the OrthoRep system, as it uses the yeast Saccharomyces cerevisiae, which ideal to express and characterize plant transporters, as the evolution platform.