Scientists from the University of Maryland say they’ve cracked one of the most important plant development processes in all of agriculture – how flowers become seeds and fruits. The researchers at UMD’s Department of Cell Biology and Molecular Genetics say the finding are especially important at a time when global warming is impacting food production worldwide.
The aim of the study was to learn how pollination triggers a flowering plant to start the fruit development process. “Understanding this process is especially important because common food crops—such as peanuts, corn, rice and strawberries—are all fruits and seeds derived from flowers,” said Zhongchi Liu, the study’s senior author and a professor of cell biology and molecular genetics at UMD.
For those that need a biology refresher, pollination is the act of transferring pollen grains from the male anther of a flower to the female stigma, later enabling fertilization and the successful production of seeds and fruit. Flowering plants are known as “angiosperms,” which is derived from the Greek words angeion (‘container, vessel’) and sperma (‘seed’), and refers to those plants that produce their seeds enclosed within a fruit. They are by far the most diverse group of land plants with approximately 300,000 known species.
Liu and her team approached the research with an underlying theory that an internal communication system was responsible for signaling the plant to develop fruit, though they were unclear how pollination triggered triggered that system. They used strawberries for the study, which are particularly suited to fertilization modeling due to the fact that their seeds are on the outside, according to Liu. “This made it easier for us to view the seeds and extract genetic information from them at multiple stages of plant development.”
The research led Liu and her team to a gene called “AGL62,” which is universally found in all flowering plants. According to Liu, AGL62 stimulates the production of an essential plant growth hormone called auxin. Once the gene activates, auxin is synthesized to prompt the creation of seedcoat (the outer protective layer of a seed), the endosperm (the part of a seed that provides food for a developing plant embryo) and fruit.
To prove the concept, the researchers used CRISPR to disrupt AGL62 function. As a result, the strawberry plants exhibited a significant reduction in auxin production and were unable to develop fruit and seeds. CRISPR was also used to generate AGL62, which resulted in normal vegetative growth and fruit development.
Auxin’s role in regulating endosperm growth is especially significant for researchers because it impacts the size of the grain and enlargement of the fruit. As Liu explains, “More auxin can boost grain size and stimulate fruit enlargement. When there’s less auxin, endosperms are unable to feed plant embryos properly and we end up with lowered crop productivity—smaller or deformed fruits that aren’t commercially viable.”
Liu says the discovery of this critical relationship between AGL62 and the production of auxin could allow agriculturalists to switch on the gene using biotechnology, bypassing pollination altogether—in other words, create “virgin” fruits. This could be especially important in the future if global temperatures continue to climb because extreme heat can kill both pollen and pollinators. “Learning more about the AGL62 gene has given us new insight into how to potentially increase the productivity of agricultural crops, particularly the ones that make up our food supply,” said Liu. (Source: University of Maryland, Nature)
