In this article let’s see 5 facts about centrioles in plant cells
Centrioles are rod-shaped organelles that are present only in lower plants and animal cells; absent in higher plant cells.
Do Eukaryotic Plant cells have centrioles?
Centrioles are present only in the prokaryotic plants and they are absent in eukaryotic plant cells.
Prokaryotic plant cells like mosses, ferns, and cycads contain centrioles that help in cell division.
Why do plant cells not have centrioles?
Plants do not have centrioles; they are present only in animals. The centrioles are used as a base for the formation of cilia; which are used in animal cells for movement and cell signaling. Plants don’t have ciliaand they do not require centrioles.
Animal cells need centrioles to pull the parent cells into two new daughter cells whereas in plant cells the cytoplasm spreads and a new cell wall is formed in the center that leads to the formation of two new cells.
How do plant cells divide without centrioles?
The mitotic spindles are responsible for organizing and sorting the chromosomes during cell division. The spindle apparatus is generally formed from the microtubule-organizing centers (MTOs) that are present in most eukaryotic cells.
In animal cells, the spindle fibers are formed from the centromeres that contain centrioles but plant cells lack centrioles.
The plant cells have a rigid cell wall that undergoes a major change in shape during mitosis (cell division) and the wall itself organizes the microtubules and forms spindle fibers during cell division. During cell division, the Golgi apparatus build special vesicles in plant cells called phragmoplast that fuse to form a cell plate.
Are centrioles necessary for spindle formation?
At the beginning of the cell division, the centrioles are positioned at the two poles of the cell and form long protein fibers called microtubules in all possible directions leading to the formation of a spindle.
The spindle fibers formed by the microtubules play an essential role in the segregation of sister chromatids and the movement of the chromosomes during the mitotic and meiotic division. It is during the prophase the spindle fibers are formed and during the metaphase of the cell division, they radiate from the centrioles in the opposite direction. These fibers either attach to the kinetochores of the chromosome or the arms of the chromosome.
The microtubules are polymers of tubulin; they are part of the cytoskeleton that gives shape to the eukaryotic cell.
Spindle fiber assembly in plant cells?
The microtubule organization is different when compared to animal cells. The stages involved in the assembly are:
- G2 phase
In the G2 phase of the cell cycle, the microtubules are formed in the peri-nuclear area by two mechanisms. In the first mechanism, many protein complexes present near the nuclear envelope associate with the augmin complex and promote the nucleation of microtubules, in this case, the microtubules grow away from the nucleus.
In the second mechanism, the Histone H1 complex is bound to the ends of the microtubules. It is associated with motor activity by pushing the fibers away from the surface.
The development of the future cell plate is determined in this phase by the formation of a narrow band of cortical microtubules. Further, the microtubules radiating in the cytoplasm are redistributed as small asters along with the nucleus. Later they converge into two opposite poles circling the prophase nucleus and forming two polar caps. In this stage, all the perinuclear fibers disappear.
During the prophase, the free perinucleated microtubules are translocated to the poles by the motor action of microtubule bundling proteins. The fibers now form a “pro-spindle” near the nucleus.
The pro-spindle microtubules formed during the prophase exert pushing force on the nuclear envelope causing it to break down and facilitating the kinetochores to form spindles. Following the nuclear envelop breakdown the spindle fibers broaden and fragment. The microtubule motor collectively establishes the bipolar spindle symmetry at the poles of the cell.
In this manner, the spindle fibers are organized during cell division in plant cells.
Centrioles play an important role during cell division and they are present only in lower plant and animal cells, they are absent in eukaryotic plant cells.