Despite decades of research, the process of plant seed formation continues to surprise scientists. In a groundbreaking discovery, researchers from Nagoya University in Japan have identified an entirely new plant tissue—something that has remained undetected for over 160 years.
This newly discovered tissue, which resembles the shape of a rabbit, is the first of its kind to be identified since the mid-19th century. It plays a critical role in seed development, particularly in the transfer of nutrients after fertilization. At the center of this discovery is a structure now called the Kasahara Gateway, a crucial mechanism that regulates nutrient flow to the developing seed.
Fertilization is essential for the growth of the hypocotyl, the part of the plant embryo that will become the seedling’s stem and root. Only when fertilization is successful can the hypocotyl access vital nutrients from the parent plant. This new discovery helps explain how plants recognize fertilization success and decide whether or not to invest energy into seed development—a key insight for agriculture and food production.
The breakthrough was made by researchers Ryushiro Kasahara and Michitaka Nodaguchi, who noticed a previously unseen tissue that appeared only after fertilization. They observed that in unsuccessful fertilization cases, the Kasahara Gateway closes, sealing off the embryo with a substance called callose, effectively stopping nutrients and hormones from entering. Without these, the embryo cannot grow and ultimately dies.
However, when fertilization succeeds, the hypocotyl detects it and initiates the breakdown of callose, opening the gateway. This allows a steady flow of nourishment to the embryo, fueling its development into a viable seed.
“By comparing nutrient flow, we saw that only successfully fertilized embryos received resources—unsuccessful ones were completely blocked off,” Kasahara explained. “This prevents the plant from wasting energy on seeds that won’t develop.”
Further investigation revealed a gene called AtBG_ppap, which is active only in fertilized hypocotyls. This gene produces an enzyme that breaks down callose, allowing the Kasahara Gateway to open. When researchers artificially increased the activity of AtBG_ppap, the gateway stayed open longer, enabling more nutrients to flow in.
The results were striking. Rice plants engineered to keep the gateway open produced seeds that were 9% larger, while other plant species showed seed size increases of up to 16.5%. This has significant implications for crop production and food security.
This discovery not only adds a completely new plant tissue to botanical science but also opens the door to innovative ways of boosting agricultural yields by manipulating how plants allocate their resources.
By Impact Lab
