Pressurised division
How a cell divides influences how a plant looks. A new study in Developmental Cell shows how the orientation of microtubules influences were the orientation of the dividing wall in the dividing cell.
Due to their cell wall plant cells are connected to each other. In this way the orientation of a cell division influences the shape of a plant. But how a cell decides to divide lengthwise or sidewise is not completely understood. When a cell gets no additional information its division orientation depends on the shape of the cell. The longest side will be halved. Additional instructions the cell gets from proteins and hormones, but their influence appears not to be large enough. Therefore the researchers studied the effect of mechanical forces on cell divisions.
In order to study this the researchers wounded roots. Wound bordering cells quickly filled the wound. First they expand into the direction of the wound and subsequently they divide against the strict cell division routine of the root, lengthwise instead of sidewise. Actually only the wound bordering cells at the inside of the root did this.
With pressure and counterpressure cells keep their shape
Subsequently the researchers studied the orientation of microtubules during cell divisions. Microtubules are cables made of proteins that help the cell keep its shape, a bit like tent poles. They notices that the orientation of these cables overlapped with the subsequent division orientation. When they were sidewise oriented, then the division was sidewise, and were they lengthwise, then the division was lengthwise.
Noticeable was that the microtubules of wound bordering cell were just after wounding both sidewise and lengthwise oriented. But after a while they were completely lengthwise reorientated.
To decipher the influences of mechanical force, the researchers created lack of counter pressure. Also in these cells the researchers observed microtubule reorientation. Comparable with the reorientation seen in wound bordering cells.
With pressure and counterpressure cells keep their shape. Partly because these mechanical forces influence microtubule orientation. This in turn influences the orientation of cell divisions.
Literature
Hoermayer, Lukas et al. (2024) Mechanical forces in plant tissue matrix orient cell divisions via microtubule stabilization. Developmental Cell, Volume 59, Issue 10, 1333 – 1344.e4, DOI: 10.1016/j.devcel.2024.03.009
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