Researchers discovered new plant tissue which regulates nutrient flow to developing seeds

A research team from Nagoya University has identified a previously unknown plant tissue responsible for regulating seed development, marking the first such discovery in over 160 years. The newly identified structure, termed the “Kasahara Gateway,” plays a critical role in determining whether developing seeds receive nutrients from the plant, with direct implications for crop yields. The findings were published in the journal Current Biology.

Led by professors Ryushiro Kasahara and Michitaka Nodaguchi, the Japanese scientists were initially studying callose—a carbohydrate involved in plant reproduction—when they detected signals in unexpected regions of developing seeds. Upon further examination, they discovered a new tissue that forms a distinct structure, which acts as a gate controlling nutrient flow into the embryo.

“In most fertilization research, attention is paid to the pollen tube entry point,” said Kasahara. “However, we found signals on the opposite side that were particularly strong in unfertilized ovules. This led to the identification of a tissue that opens or closes depending on fertilization status.”

The structure blocks nutrient transfer in the absence of fertilization by depositing callose, creating a “closed state.” Upon successful fertilization, callose is dissolved, transitioning the tissue into an “open state” that permits nutrient flow into the developing seed. This mechanism ensures plants do not allocate resources to non-viable seeds.

To investigate the genetic regulation behind this mechanism, the team analyzed gene expression patterns in fertilized ovules. They identified a gene, AtBG_ppap, that is expressed only in fertilized seeds and is responsible for callose dissolution. When this gene was overexpressed in genetically modified plants, the gateway remained open, resulting in increased nutrient absorption and seed size.

Experimental trials with rice showed seed size increases of approximately 9%, while other crop species demonstrated gains of up to 16.5%. The researchers suggest that controlling this gateway could offer a new approach to boosting agricultural yields.

Beyond yield enhancement, the discovery also contributes to evolutionary biology. Kasahara posits that the gateway mechanism may have played a role in the evolutionary success of flowering plants (angiosperms), allowing them to conserve energy by restricting nutrient supply to fertilized seeds only.