Visualization of transport of glucosinolate hydrolase to vacuoles

January 23, 2023

Discovery of a novel enzyme transport pathway using correlative light and electron microscopy

The RIKEN CSRS took advantage of the latest electron microscopic technologies to discover the direct transport of glucosinolate hydrolase (b-glucosidase) to vacuoles without going through the Golgi apparatus in lateral root caps of Arabidopsis thaliana (Arabidopsis). The enzyme is carried in an organelle called the endoplasmic reticulum (ER) bodies, which are swelled from the ER.

In leaves of Arabidopsis, it has been known that b-glucosidase in ER bodies and glucosinolate in vacuoles are mixed when the vacuoles are broken by insect bites, leading to releasing protective substances against pests, although the corresponding mechanism in its roots remains to be understood.

The research team discovered many ER bodies in the lateral root caps of Arabidopsis using high-pressure freezing and wide-range electron microscopic imaging. Visualizing the contact area of ER bodies and vacuoles using high-pressure freezing and correlative light and electron microscopy (CLEM) revealed ER bodies contacting and fusing with vacuoles and vacuoles collapsing. These findings suggest that b-glucosidase is constantly transferred to vacuoles by ER bodies and reacts with glucosinolate in the vacuoles and that protective substances against pests are released when the vacuoles collapse.

The findings of this study would contribute to elucidating plant growth, biological defense in rhizospheres and symbiotic relationships with soil microbes.

Original article
Plant & Cell Physiology doi:10.1093/pcp/pcac177
K. Toyooka, Y. Goto, K. Hashimoto, M. Wakazaki, M. Sato, M. Yokota Hirai,
"Endoplasmic Reticulum Bodies in the Lateral Root Cap are Involved in the Direct Transport of Beta-Glucosidase to Vacuoles".
Kiminori Toyooka; Senior Technical Scientist
Yumi Goto; Technical Staff
Masami Hirai; Unit Leader
Mass Spectrometry and Microscopy Unit