The roots of the plants grow in a screwing motion - just like a drill penetrating a wall

• The researchers performed imaging at the resolution of the single cell and discovered that the movement of the drill occurs in specific cells at the tip of the root, and apparently allows the root to penetrate the soil. * The article was published in the journal Nature Communications

In an interdisciplinary study carried out at Tel Aviv University, researchers from the School of Plant Sciences in the George S. Wise Faculty of Life Sciences teamed up with their colleagues from the Sackler Faculty of Medicine in order to investigate the course of the growth of plant roots. The plant researchers used a computational model built by cancer researchers for cancer cells, and applied it to cells in plant roots.

The findings are fascinating and groundbreaking: for the first time in the world, we observed at single cell resolution that the root grows with the movement of a screw - just like a drill penetrating a wall. Following the study, the cancer researchers estimate that cancer cells also use a rotary threading movement to penetrate healthy tissues in the tumor environment, or to produce metastases in different organs of the body.

The research was led by Prof. Ilon Shani from the School of Plant Sciences and Food Safety and Prof. Ilan Zrafati from the Department of Clinical Microbiology and Immunology at Tel Aviv University, and was carried out in collaboration with researchers from the USA, Austria and China. The article was published in March 2021 in the prestigious journal Nature Communications.

The researchers in Prof. Shani's group used a model plant called Arabidopsis. They marked the nuclei of the root cells using a fluorescent protein, and followed the growth process and the movement of the cells at the tip of the root using a powerful microscope - about 1000 cells in each imaging. Also, to examine what causes and controls movement, they focused on a well-known hormone called auxin, which is known to regulate development in plants. They built a genetic system that enables auxin production to be turned on and off (like a switch), in a number of selected cells, and then followed the effect of turning it on/off on the thousand cells at the tip of the root, in four dimensions - the three dimensions of space, and the dimension of time. After each on/off of the auxin, each of the thousand cells was videotaped for 6 to 24 hours, thus accumulating a huge amount of video material.

In the next step, the researchers used the computational tools made available to them by Prof. French developed in his laboratory, for the purpose of monitoring the development of cancerous tumors, and used them to analyze the imaging files obtained in the experiment. In fact, for the first time, they were able to observe with their own eyes the twisting movement of the root, as well as accurately quantify and map about 30 parameters of root growth in time and space - among them acceleration, length, changes in cell structure, coordination between cells during growth and speed of movement - this for each of the thousand cells at the tip the root The findings even allowed them to accurately assess the movement and effect of auxin in the root, and the way in which it controls the growth process.  

Prof. Shani: "Plants pose special challenges to us researchers. For example, half of the plant, (the hidden half), i.e. the root system, is hidden in the soil. The computational tools developed for cancer research allowed us for the first time to precisely measure and quantify the kinetics of growth and reveal the mechanisms that control it at single-cell resolution. In doing so, they significantly promoted plant research, a field of utmost importance to society - both in the environmental aspect, and in regards to promoting agriculture and feeding the population."

Prof. Shani adds: "During the research we discovered a fascinating phenomenon that had not been observed until now in 'Live': we saw that the cells at the end of the root move in a twisting motion, like a drill penetrating the soil. We also identified that the hormone auxin controls the root tip screwing process. We studied and measured the directions of movement of the hormone auxin which moves from cell to cell in the root, in order to control the growth of the root and the screwing movement.

Prof. Sarfati adds: "This is a synergistic cooperation that empowers and educates both parties. In plants, the processes occur much faster, so they are an excellent model for us. Following the findings of the research in plants, we are now testing the possibility of a similar screw movement in cancer cells and metastases, during their penetration into the adjacent health tissue."

for the scientific article

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