Knowing why something happens is one thing. Knowing how it happens is another.
Supported by a research grant from the National Science Foundation (NSF), Dr. Jennifer Blake-Mahmud of the Hope College biology faculty has launched a new study to reveal the genetics behind a curious biological phenomenon: plant sexuality. The vast majority of plants are both male and female at the same time, like Easter lilies. Fewer than one in 10 plant species have separate male and female plants, like holly. But in some rare species, being male or female isn’t a fixed thing and plants can change sex during their lifetimes. It’s an interesting mystery for a biologist to solve, but Blake-Mahmud noted that it’s also an important one.
“In some of these species, the environment affects whether plants become male or female,” said Blake-Mahmud, an assistant professor of biology. “We know sex expression can be affected by light in some species, or even how big the plant is, but we don’t know anything about how this works genetically. What genes are turned on and what genes are turned off is a total mystery.”
“On the broader scale, if you care about ecosystems, understanding how the environment is affecting reproduction in plants is important,” she said. “Many economically important crops have separate sexes, and often one sex is more preferred than another, like female holly or male gingko. Understanding more about how gene expression relates to expressed sex will help make more economical decisions and plan for population stability in the face of climate change.”
Blake-Mahmud explained that most individual plants — representing more than 90% of all plant species — carry both male and female reproductive parts. In contrast, the pattern is reversed for most animal species, with less than 10% having two functioning sets of male and female parts.
For most species that have separate sexes, she said, the individual’s sex stays the same once it’s been determined. A relatively small number, though (including some plants, some fish, and gastropods such as limpets), may change sex during their lifetime depending on what’s happening around them.
Examples of the latter include the plant on which Blake-Mahmud and her team of student researchers are focusing: the striped maple, which is native to Michigan. The team spends several weeks camping in the field every summer collecting data and plant tissue samples from trees in the wild. They then extract the RNA, which is sent to an outside laboratory. After reading the RNA, the laboratory will send back files that detail what RNA is present in each plant. Blake-Mahmud will analyze these data with the help of her students for insight into the genetics involved in sex determination.
Although she and her students are seeking answers to new questions, Blake-Mahmud emphasizes that they are building on related work done by others — just as she hopes that the work she and her team are doing will one day prove a foundation for someone else.
“There are people who have made it their career to work on the genetics of plants or the genetics of species,” she said, “not to mention ecological work on this species conducted by other researchers. We will build on previous plant genetics work that has been done and expand it to answer this important, and currently unknown, question.”
Blake-Mahmud’s research is supported through a $501,356, three-year grant through the NSF’s “Building Research Capacity of New Faculty in Biology (BRC-BIO)” initiative. She is mentoring the students on the research team as they work part-time during the school year and full-time during the summer.
Her student team during the remainder of the spring semester consists of freshmen Steven Awad and Sam Hodgson, and senior Olivia Thomas. Two students will conduct research with her full-time this summer, with four working part-time next fall.
The project was one of two at Hope to have received grants through the BRC-BIO program this past fall, out of only 20 awarded nationwide. Biologist Dr. Kelly Ronald and chemist Dr. Natalia Gonzalez-Pech are seeking to gain insight into the global decline in bird population by studying how house sparrows are affected by a specific type of air pollution: iron oxide nanoparticles (IONPs), floating bits of iron generated by the iron and steel industries that are so small that a standard microscope cannot see them.