Central China Normal University

Using a mobile stamen to slap away insect visitors maximizes pollination and minimizes costs to flowers, a study shows. For centuries scientists have observed that when a visiting insect's tongue touches the nectar-producing parts of certain flowers, the pollen-containing stamen snaps forward. The new study proves that this action helps increase the flower's reproductive success while reducing the costs of insects lingering too long and feeding on the flower's nectar, similar to in a restaurant, where table turnover is crucial to maximise profits. "We tested three scenarios," says lead author Deng-Fei Li, a PhD student at the Institute of Evolution and Ecology at the School of Life Sciences, Central China Normal University, Wuhan, China. "These included whether snapping stamens help flowers by controlling how much pollen each insect takes, filtering out less proficient pollinators, or reducing the amount of nectar taken by each visitor." Li and colleagues immobilised the stamen of the flowers of barberry bushes by dipping the floral pedicel in an alcohol bath for 35-45 minutes. They confirmed that the alcohol treatment, or the lingering smell from the alocohol, did not deter pollinators. They then compared the behaviour of insects and the pollination success of flowers with mobile or immobilised stamens under glass containers in the laboratory and directly outdoors. They also stained the flowers' pollen to track how efficiently insects transported it to other nearby flowers. Their work showed that insects visiting flowers with immobilised stamens stayed 3.6 times longer and removed more nectar than those visiting flowers with mobile stamens. However, the insects deposited 2 times fewer pollen grains per flower visit than insects visiting flowers with mobile stamens. Additionally, the team found that insect visitors deposited pollen from flowers with mobile stamens on about 3 times more flowers, and on flowers further away, increasing the likelihood of reproductive success for the plant. The team did not find evidence that the slapping stamens helped exclude less helpful pollinators. All five species of bees and flies that were tested on visiting the flowers stayed about four times longer on flowers with immobile stamens. "Our study helps resolve the mystery of the purpose of insect-triggered movement of flower parts that has troubled botanists since Linnaeus first observed mobile stamen in 1755," explains senior author Shuang-Quan Huang, professor at the Institute of Evolution and Ecology at the School of Life Sciences, Central China Normal University. "We've shown that plants use rapidly moving stamens to enhance the turnover of bees and flies on their flowers, thereby reducing their nectar costs per successfully transported pollen grain."

Adding an ingredient called an adjuvant can help vaccines elicit a more robust immune response, better training the body to fight a pathogen. Researchers report a substance that boosted the immune response to an experimental COVID-19 shot in mice by 25 times, compared to injection with the vaccine alone. Ironically, some vaccines need their own "boosters." Adding an ingredient called an adjuvant can help vaccines elicit a more robust immune response, better training the body to fight a pathogen. In a new study in ACS Infectious Diseases, researchers report a substance that boosted the immune response to an experimental COVID-19 shot in mice by 25 times, compared to injection with the vaccine alone. Although the first COVID-19 shots authorized in the U.S. apply cutting-edge genetic technology, the tried-and-true strategy of using proteins from the pathogen can produce vaccines that are less expensive to make and easier to store. So far, the U.S. Food and Drug Administration has authorized only one protein-based vaccine, made by Novavax, against SARS-CoV-2. However, many currently available inoculations against other diseases rely on proteins or pieces of them, and these shots contain adjuvants to enhance their effect. Researchers have found that molecules derived from α-galactosylceramide (αGC), a compound from marine sponges, can act as adjuvants by stimulating a small population of immune cells important for defending the body against viral infections. Rui Luo, Zheng Liu and their colleagues wanted to see if they could devise a version of αGC to significantly boost the immune response elicited by a protein-based COVID-19 vaccine. The team made four analogs of αGC and added each to an experimental vaccine containing a piece of SARS-CoV-2's spike protein, which the virus uses to infect cells. The researchers gave mice three injections over 29 days and tracked their immune response out to 35 days. To measure the effects of the adjuvants, they looked at various aspects of immune function, including two ways the immune system eliminates pathogens: through antibodies, which are immune proteins that latch onto an invader, and T cells, which kill diseased cells. None of the four meaningfully enhanced the T cell response, but all of them produced antibodies with a much greater capacity for interfering with the virus. The analog called αGC-CPOEt led to the production of antibodies with the greatest neutralizing capacity -- 25 times greater than what the vaccine could elicit without an adjuvant. These results suggest αGC-CPOEt merits further investigation as a potential adjuvant to fight COVID-19 and other infectious diseases, the researchers say. The authors acknowledge funding from National Natural Science Foundation of China, Central China Normal University, Fundamental Research Funds for the Central Universities from Huazhong Agricultural University, and the Program of Introducing Talents of Discipline to Universities of China.