By Kay Ledbetter
Dr. Sakiko Okumoto has her eye, or specifically her microscope, trained on tiny protein-based fluorescent sensors that track amino acids in live plant cells.
Okumoto is the newest faculty member in Texas A&M University’s soil and crop science department in College Station and will be working as a plant physiologist with Texas A&M AgriLife Research.
She earned her bachelor’s and master’s degrees from The University of Tokyo, Japan, and her doctorate from Tübingen University, Germany. Prior to joining Texas A&M, she was trained as a postdoctoral fellow at the Carnegie Institution of Washington for four years, and was a faculty member in the department of plant pathology at Virginia Tech for nine years.
Okumoto has concentrated both her teaching and research interests in the development of biosensors for small biological molecules; nitrogen transport and sensing in plants; and improving nitrogen utilization efficiency of plants.
“The overall goal of my research is to understand how nitrogen, quantitatively the most important nutrient in crops, is managed in plants,” she said. “Specifically, my research aims to determine how amino acids, one of the main forms of organic nitrogen in a plant body, is transported.”
Okumoto explained that nitrogen is required in bulk to make proteins and nucleic acids, DNA and RNA, among other things. Amino acids serve as the “currency” of nitrogen in a plant body and circulate all the time between different organs.
“We try to understand how amino acids move from one organ to another and how much they move,” she said. “Then we use that knowledge to improve crop plants, for example, increasing the quality and quantity of nitrogen in the plant parts we eat, such as seeds and tubers.”
Her work is initially being done on the model plant, Arabidopsis, which is a member of the mustard family.
“However the principle we discover will be applicable to other crops, because the mechanisms to transport amino acids seem to be mostly shared among different species of plants, including crops and weeds.”
Okumoto said protein-based, fluorescent sensors are powerful tools to study such mechanisms. The sensors provide a method to trace the movement of amino acids or other molecules in specific compartments within live cells, which is near impossible otherwise.
“Also we can purify the sensor protein from bacteria and use it as a cheap and efficient method to detect amino acids in a complex sample.
“We utilize these sensors to discover novel molecular mechanisms that are involved in the regulation of amino acids,” she said. “We are currently interrogating the processes in which amino acid exporters are involved using various genetic resources such as T-DNA insertion mutants and gene editing tools. We are also interested in developing novel sensors for other biologically important molecules.”
Okumoto said they have discovered multiple transporters that export amino acids from plant cells.
“It has long been known that certain plant cells are capable of exporting amino acids – seed coats and the cells at the surface of the root, for example. But we had no idea what kind of transporters were involved. The work we have conducted so far assigns specific proteins for those functions.
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