GAINESVILLE, Fla. — The Chinese brake fern accumulates huge quantities of arsenic, but one of its genes caused a model plant to do just the opposite, a discovery that surprised University of Florida scientists and could lead to low-arsenic rice varieties.
A UF study, published online this week in the journal Plant, Cell and Environment, showed that when mouse-ear cress plants with the added gene were grown in arsenic-laden soil, their leaves contained as little as one-seventh the arsenic of control plants.
The study raises hopes that UF researchers can get similar results by putting the gene into rice plants, said Bala Rathinasabapathi, an associate professor with UF’s Institute of Food and Agricultural Sciences and co-author of the paper. If so, it could lead to new varieties for countries such as China and Bangladesh, where rice is a staple and the grain often absorbs arsenic from soil and water.
“In rice, it’s a very important problem,” he said.
Rice is the only crop plant that accumulates arsenic to a notable degree, said Rathinasabapathi, of the horticultural sciences department. When consumed even in small amounts over time, the toxic heavy metal increases cancer risk.
Arsenic has been used in pesticides, herbicides and wood preservatives. In some areas, residual arsenic from these products contaminates soil. In others, naturally occurring arsenic contaminates drinking and irrigation water used by millions.
The brake fern probably has many genes that allow it to absorb arsenic and survive, Rathinasabapathi said. So far, UF researchers have pinpointed one, a gene involved in production of glutaredoxin, a protein that helps plants deal with environmental stress.
This study was the first attempt to put that gene into another plant, he said. It was partly funded by an IFAS Research Innovation Award Rathinasabapathi received, amounting to about $12,500.
Other authors of the paper were Sabarinath Sundaram, a former UF postdoctoral associate now with Texas A&M University; Shan Wu, a UF biological scientist; and Lena Ma, a professor with UF’s soil and water science department.
Rathinasabapathi isn’t sure why the gene prevented cress plants from accumulating arsenic.
“Ferns are generally not very well investigated, genetically,” he said. “There may be many genes in the brake fern that will help with stress tolerance and may be helpful in improving crops, that is the overarching theme to my research program.”
The UF study is an interesting step, but there are challenges in producing viable low-arsenic rice varieties, said Andrew Meharg, biogeochemistry chair with the University of Aberdeen’s School of Biological Sciences in Scotland.
The mechanisms that control the arsenic content of rice grain are poorly understood, he said. If transgenic varieties were developed, they would need to outperform existing varieties in arsenic resistance and grain yield.
Meharg, an internationally known arsenic-contamination authority, analyzed white rice samples from 10 countries. He determined that residents of Bangladesh and China were at the most risk, based on the arsenic content and the amount eaten.
Bala Rathinasabapathi, an associate professor with the horticultural sciences department, examines mouse-ear cress plants that have been given a gene from a fern that prevents them from accumulating arsenic