A research team has clarified how boric acid channels, which transport the essential nutrient boron in plants, are moved to the plasma membrane.
Botanists are beginning to understand the channels and transporters responsible for nutrient uptake and movement, but how do these proteins get to the right locations?
For instance, plants require boron, which is absorbed by cells through boric acid channels. The question remains: how do the proteins that create these channels reach the plasma membrane?
A research team led by Professor Junpei Takano from Osaka Metropolitan University’s Graduate School of Agriculture discovered a mutant type of Arabidopsis thaliana where the boric acid channels fail to reach the plasma membrane properly. This issue is caused by a lack of the protein KAONASHI3 (KNS3). The term kaonashi (meaning “faceless” in Japanese) was coined in 2008 by a team from Nagoya University, including Associate Professor Sumie Ishiguro, who co-authored this study.
In-depth analysis of how boric acid channels are transported showed that KNS3 and two related proteins, KNSTH1 and KNSTH2, likely create a protein complex. These complexes facilitate the journey of boric acid channels from the endoplasmic reticulum to the Golgi apparatus, and finally to the plasma membrane.
Furthermore, the pollen of Arabidopsis thaliana usually has a patterned surface resembling muskmelon skin; however, this pattern vanishes—becoming “faceless”—in mutant strains lacking the KNS3 gene, which is vital for pollen outer layer formation. This phenomenon could be tied to the improper transport of proteins other than those associated with boric acid channels.
Professor Takano remarked, “Our insights into the intracellular transport of membrane proteins suggest that plants may control nutrient absorption and pollen structure through the specific protein transport regulated by the KNS3-KNSTH1-KNSTH2 complex. These findings could contribute to strategies for lowering fertilizer use while enhancing crop productivity.”
The results of this research are featured in the Journal of Experimental Botany.
