b"Ssshh! A Quiet and Unexpected Transgene Mystery is Happening in Plant Sperm CellsSilenced genes could pose a significant obstacle in plant reproductive research.Aimee NielsonIN THE QUESTto understand plant reproduction, sci- Kawashima, associate professor in the UK Department of Plant entists often turn to gene editing, introducing new genesand Soil Sciences. We knew other groups had already identified (transgenes) into plants to study their effects. However, recentthat sperm cells in pollen have very interesting and specific gene research revealed a puzzling phenomenon in the sperm cellsregulation, that is translational repression. of Arabidopsis thaliana, a model plant in genetic studies. ThisKawashima explains that usually the mRNAs are a template discovery could be a critical finding that may reshape the under- to continuously make proteins-the final product of a cell. But the standing of plant genetics and reproduction. other groups in the study showed that a certain mRNAs in the University of Kentucky Martin-Gatton College of Agriculture,sperm cells are stored and not immediately making any proteins. Food and Environment researchers recently were exploring rolesThrough their research, his team observed RNA generation, of specific genes in plant sperm cells using transgenesartifi- but no proteins. They reran many tests, believing the finding was cially introduced geneswhen they stumbled upon somethingan experimental error. unexpected: certain transgenes becoming silent. Specifically, when genes encoding proteins without specific locations inside the cell (cytoplasmic proteins) were introduced into Arabidopsis sperm cells, they became transcriptionally or post-transcription-ally silenced. This means their mRNA, the blueprint for producing proteins, was significantly reduced, leading to an absence of theIts a biological phenomenon that is specifically expected proteins.We are trying to understand plant reproductive biology fromhappening in the sperm cell. both the male side and the female side, said Tomo Kawashima,Tomo Kawashimaassociate professor in the UK Department of Plant and Soil Sciences.Silent but Potentially Destructive PhenomenonScientists have named this mysterious silencing phenomenon Gene Silencing based on ENcoded protein's Intracellular locali- Surprisingly, we found that our transgenes did not even zation (GESENI). GESENI refers to the unexpected silencing ofmake mRNAs, which is different from the discovery from the transgenes in the sperm cell, a process independent of the plant'sother groups, he says. We tested many times and we thought major gene-silencing machinery, including DNA methylation. at the beginning we made experimental errors. This discovery isn't just a technical hiccup; it has far-reachingThe transgene itself was functional, Kawashima continues. implications. It challenges the current understanding of geneAlthough it was functional, it was not generating any proteins regulation in plant reproduction. It suggests that there's aninside the sperm cell. We discovered that when we try to express unknown mechanism at play, selectively silencing certain genesa transgene in a sperm cell, if the encoded protein lacks a spe-in sperm cells.cific tag, it doesn't produce any detectable signals. We tested it My research is aimed at trying to understand plant repro- in different cell types. Its a biological phenomenon that is spe-ductive biology from both male and female side, says Tomocifically happening in the sperm cell.40/ SEEDWORLD.COMINTERNATIONAL EDITION 2024"