Division of Plant Science and Technology
E-mail: mittlerr (at) missouri (dot) edu
Office address: 371I Bond Life Sciences Center
Office phone: 573-882-7077
1. The ROS Wave and Ultrafast Omics Responses to Abiotic Stress
Systemic signaling pathways enable multicellular organisms to prepare all of their tissues and cells to an upcoming challenge that may initially only be sensed by a few local cells. They are activated in plants in response to different stimuli including mechanical injury, pathogen infection, and abiotic stresses. Key to the mobilization of systemic signals in higher plants are cell-to-cell communication events that have thus far been mostly unstudied. My recent discovery of systemically propagating reactive oxygen species (ROS) waves in plants has unraveled a new and exciting cell-to-cell communication pathway that, together with calcium and electric signals, could provide a working model to how plant cells transmit long-distance signals via cell-to-cell communication mechanisms. My study of rapid systemic signaling has also focused my attention on rapid local responses to stress and on the cross talk between ROS, ABA and stomatal responses. These have brought me to formulate another hypothesis on plant systemic responses called the leaf autonomous response pathway. Supported by IOS-1353886 and IOS-1063287.
2. Stress Combination
Abiotic stress is the primary cause of crop loss worldwide, with losses in the US estimated at 14-19 billion dollars each year. While abiotic stress is routinely studied in plants by applying a single stress condition such as drought, salinity or heat, this type of analysis does not reflect the conditions that occur in the field or in nature in which crops and plants are subjected to a combination of different stresses (e.g., drought and heat). Because abiotic stress combinations had the outmost devastating economical and sociological impacts on the US, with losses of 48.4 and 61.6 billion dollars in 1980 and 1988 respectively, and because these extreme weather events are likely to increase in frequency due to global warming, the development of transgenic crops with improved tolerance to abiotic stress combinations is a highly important goal that would provide a promising avenue to reduce yield losses and secure food supply for our growing population. My initial studies into abiotic stress combinations in plants demonstrated that the response of plants to a combination of two different stresses is unique and cannot be directly extrapolated from the response of plants to each of the different stresses applied individually. I have also identified several key regulatory proteins required for the acclimation of plants to stress combinations. I am currently working towards the identification of important regulatory networks that mediate the acclimation of plants to abiotic stress combinations, as well as towards the development of plants and crops with enhanced tolerance to stress combination. Supported by IOS-0820188.
3. Regulation of Cell Survival and Death Pathways by Fe-S Proteins
Maintaining iron and reactive oxygen species (ROS) homeostasis is essential for cellular proliferation, stress responses, and the regulation of cell survival and death pathways in plant and animal cells. The recent discovery of a novel group of Fe-S containing proteins with a redox-sensitive labile 2Fe-2S cluster in plant and animal cells (NEET proteins), provides one of the first links between the regulation of iron levels and ROS homeostasis in cells. Our studies show that the function of NEET proteins is both ancient and essential for proper iron/ROS/Fe-S mobilization in cells. We propose that NEET proteins use their redox-active labile clusters to sense the levels of ROS/redox in cells, and depending on these levels they either promote cellular proliferation, or trigger the activation of apoptosis and autophagy. We recently discovered that the degree of lability of the NEET’s 2Fe-2S clusters and their overall protein levels in cells are crucial for making this decision, and have shown using different mutants and other molecular tools that cancer cells that accumulate high levels of wild type NEET proteins (but not mutant NEET proteins with a high cluster stability) are protected from oxidative stress and can proliferate faster. Our findings establish a key role for NEET protein overexpression in promoting the tumorigenicity of breast cancer cells. Furthermore, they provide a mechanistic foundation for the role of NEET overexpression in multiple cancer types, including breast, prostate, gastric, cervical, liver, and laryngeal cancers. We are currently working toward developing different therapies (drugs, peptides), as well as different delivery methods (nanoparticles) that will target the stability of the 2Fe-2S cluster of NEET proteins, thereby alter the redox/ROS levels of cells. These would be applicable not only for the treatment of different cancers that rely on high expression levels of NEET proteins for their proliferation, but also for the treatment of diabetes and certain neurodegenerative diseases that have also been linked to NEET protein overexpression. Supported by MCB-1613462 and IOS-1557787; proposals pending with NIH.