Taking a breather: Characterizing the role of H+/Ca transport in anoxia tolerance

Plants experience a dynamic environment where numerous stress conditions may be encountered. For example, flooding induces several stresses: limited oxygen availability, changes in temperature, reduced light. Anoxia, the removal of oxygen, is a consequence of waterlogging and submergence of plants.

During this stress, plant tissues significantly reduce the rate of energy production, affecting many aspects of metabolism. This project examines how fluctuations in calcium (Ca) within plant cells can impact anoxia tolerance. The investigators have discovered that removal of a specific Ca transporter appears to buffer the plant against anoxic conditions.

Here imaging experiments will visually address how this change effects how Ca moves, where it is localized, and how the temporal and spatial changes in Ca can impact anoxia tolerance. To complement these photographic approaches, biochemical and genetic experiments will address the mechanisms of Ca movement. Approaches to measure changes in protein and nucleic acids will be used to further define how removal of a specific Ca transporter can impact the plant’s utilization of energy.

One broad impact of this work will be the development of a unique research collaboration with faculty and students from Houston Community College (HCC). HCC is an open-admission, public school that while serving one of the most diverse populations in the US, does not usually provide research experiences. These HCC students will both learn and contribute to this project.

The efforts of this work will lead to a better understanding of how plants adapt to their environment. In the future, engineering-modulated Ca movement in plants could circumvent adverse effects of anoxic conditions to mitigate climate change-induced crop loss.

Oxygen deficiency (hypoxia) and absence (anoxia) are severe physiological stresses in plants. Most commonly they occur when extreme weather events lead to flooding, which causes widespread crop losses. Membrane transporters may be essential components of anoxia tolerance because they are involved in signal transduction and regulation of metabolic processes.

Mutations in the Arabidopsis vacuolar cation/proton exchangers (CAXs) cause striking tolerance to anoxia. This robust phenotype was unexpected: a loss-of-function mutation causing a gain of function. The majority of CAX RNAs are unchanged during hypoxia, highlighting the limits of RNA profiling as an exclusive means of gene discovery.

A series of genetic, omics, membrane transport, physiological, cell and elemental imaging experiments will be used to characterize the role of CAXs during anoxia that will demonstrate their role in signaling, cation transport and metabolism. A highly skilled, diverse team will use a multi-disciplinary approach including plant genetics, membrane transport and elemental imaging.

As part of the broader impacts, and as a further means of discovery, a Course-based Undergraduate Research Experience (CURE) at Houston Community College (HCC) will be implemented. HCC is an open-admission public school that, while serving one of the most diverse populations in the US, does not typically provide research experiences. In short, characterizing the role of CAXs in anoxia tolerance will lead to a greater understanding of plant signal transduction.

Furthermore, this knowledge will eventually aid in the development of flood-resistant crop plants, reducing crop loss during extreme weather events.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.