Kobe University scientists report that variants of a major latex-like protein, secreted into plant sap, help explain why pumpkins, squash and other cucurbits draw hydrophobic pollutants into their edible parts—an insight that could guide safer crops and soil-cleanup strategies.
Researchers at Kobe University say they have uncovered why some gourds accumulate soil pollutants in their fruits: a transport protein variant that is secreted into xylem sap shuttles contaminants upward through the plant. The work centers on major latex-like proteins (MLPs) and was described alongside a new paper in Plant Physiology and Biochemistry. (sciencedaily.com)
Members of the Cucurbitaceae family—including pumpkins, squash, zucchini, melons and cucumbers—are known to concentrate hydrophobic pollutants in aboveground tissues, sometimes at levels that raise food-safety concerns. Prior studies have linked this tendency to specific MLPs and documented contamination with persistent organic pollutants such as dioxins, PCBs and organochlorine insecticides. (pmc.ncbi.nlm.nih.gov)
“The pollutants don’t easily break down and thus pose a health risk to people who eat the fruit. Interestingly, other plants don’t do this and so I became interested in why this happens in this group specifically,” said Hideyuki Inui, an agricultural scientist at Kobe University. (sciencedaily.com)
Earlier research from Inui’s group and collaborators identified MLPs in zucchini that bind hydrophobic contaminants and enable their movement in plant sap; related work has shown these proteins’ binding behavior can vary with conditions. (pmc.ncbi.nlm.nih.gov)
The new study focuses on why some cultivars accumulate more pollution than others. According to Kobe University, protein variants found in high-accumulating plants are secreted into the sap, while others remain inside cells. A small change in the amino acid sequence acts like a tag, directing secretion. When the team expressed the high-accumulation protein in tobacco, the protein was likewise exported to sap—supporting the mechanism. “Only secreted proteins can migrate inside the plant and be transported to the aboveground parts. Therefore, this seems to be the distinguishing factor between low-pollution and high-pollution plant varieties,” Inui said. (kobe-u.ac.jp)
The researchers say controlling these transport proteins—by altering their pollutant binding or their secretion into sap—could help breed crops that avoid concentrating harmful chemicals in edible parts. They also see potential for phytoremediation, using engineered plants to clean contaminated soils. “I started this research because I was looking for plants that can detect and digest pollutants effectively,” Inui added. (sciencedaily.com)
Kobe University notes that the project received support from the Japan Society for the Promotion of Science (Grant-in-Aid 23241028) and the Murao Educational Foundation. (kobe-u.ac.jp)