In many species reproduction is dependent upon two adults combining to form a new organism. In this case, both parents create sexual cells (gametes) that join together to form an embryo, which then forms the new person(s).
Although this type of reproduction is widespread in multicellular organisms but it is also the case in the unicellular species. In addition to sexual reproduction, certain organisms have the ability to reproduce asexually. Contrary to sexual reproduction, this type of reproduction involves only one parent in order to produce offspring.
Based on the species There are a variety of asexual reproduction such as fragmentation, fission and budding, among others. This article focuses on budding, a kind of asexual reproduction. It examines the way in which it occurs in various kinds of organisms.
Definition of Budding
Budding is an example of asexual reproduction in which an organism (offspring) develops as an outgrowth from the mother’s body. The new organism begins to grow as a tiny body that is attached to the parent and increases in size and remains connected to the parent.
At first it appears to be part of the parent due to the fact that it is not able to separate until it grows. In the end, the new individual that is similar to the parent separates and becomes an independent entity.
This method of reproduction is found in many multicellular and unicellular organisms such as Bacteria, Hydra, Fungi eg Yeast , Plants
Budding in Fungi
- The process of budding in yeast cells begins by softening one small part of the cell’s wall. Then, it is followed by the formation of a tiny protuberance within the region. At this point this protuberance (bud) is approximately 1um across at its widest point and is completely covered in the cell walls of the mother cell.
- While at the same time the nuclear division (of cells that are parent) occurs in a way it is possible that genetic information from the parent cell is transferred to the new buds.
- In addition to nuclei, additional organelles of the cell, such as mitochondria, the endoplasmic-reticulum, ribosome, as well as other cytoplasmic elements are transported into the bud region as it grows in size.
- During budding, the replication of DNA from the parent genome occurs through the S-phase which is characterised by DNA synthesis, and the M-phase in which the DNA copy is made.
- The constriction site is in between the cell wall of the mother and the bud, studies have demonstrated an ring of chitin to grow (at the surface of the cell wall). The chitin ring expands and the septum begins to expand inwards and the plasma membrane to expand, and forms the primary septum.
- The development of secondary septums is accompanied by the dissociation of two cells, with the primary septum that is chitinous remaining with the mother. The mother is left with an elongated scar (bud scar) in the area where the bud split.
- After the yeast cell has split from the parent cell/mother and the parent cell can begin the budding process. But, the new cell needs to mature (and attain the same size as the mother cell and parent) prior to being able to begin budding.
- Often, the new cell will likely begin creating a new bud even before it’s separated from its parent cell. In this case, the daughter cell expands in size but doesn’t split it from its parent.
- When it reaches a certain size and matures the new bud begins developing as mentioned above. This new bud is likely to expand in size and begin to produce new buds before it can be separated from the cell that it is derived from.
- Repeating this process the budding process produces what appear to be yeast-like chains cells. While budding the parent cell could be able to start producing new buds, which causes it to appear to be branched. This is known as the pseudomycelium . It consists of cells that are loosely connected and can easily split off over the course of time.
- In the event that there are unfavorable environmental conditions, the cells create spores capable of being able to survive in harsh conditions.
- Based on environmental conditions such like temperature, nutrition etc the budding cycle can range from a minute to several hours.
Budding in Bacteria
- Bacteria is a microscopic, unicellular organism that can be found in many environments around the globe (aquatic and terrestrial).
- Bacteria, many other organisms on Earth, has a simple internal structure that lacks a membrane-bound nucleus.
- They are called prokaryotes. There are many kinds of bacteria. They are classified based on their nutrition, general morphology and where they are located.
- Binary fission is the most common mode of reproduction. However, budding bacteria can also be reproduced by some species.
- Some examples of budding bacteria are: Hyphomicrobium and Rhodopseudomonas. Ancalomicrobium. Planctomyces. Cyanobacteria.
- Budding bacteria attaches to most surfaces in their environment.
- Some bacteria species begin the budding process with de novo wall formation at certain points in the parent cell. This normally occurs at the pole end of the bacteria.
- The important step of de novo synthesis within the wall is crucial in the budding process. This ensures that the daughter cell doesn’t use the cell envelope material from the parent. The next step is DNA replication, which is followed by the separation of mother and daughter cells. This is called the bacterial budding cycle.
- This process is seen in stalked bacteria such as Hyphomonas nutunium. The stalk acts as the reproductive organelle.
- Cytokinesis is the division of the cytoplasm during cell differentiation to create two new cells. These cells can then give rise to stalked (non-motile), and swarmer (flagellated, capable of swimming) cells.
- The stalked cells can enter the budding cycle but swarmers must differentiate into stalked cell before they can do so. The stalk is formed, which results in the production of the bud. The bud, just like yeast, begins to grow and is eventually separated from its parent cell. This allows it to develop into an independent organism capable of budding.
- The stalk is the part of the cell that connects the mother/parent cell to the buds for stalked bacteria.
- Cell division takes place at the junction of the stalk and the bud.
- H. neptunium is a prokaryote and has one strand of circular DNA that measures 3.7 Mb. It is replicated in two steps during budding.
- The first step is to move one of the centromere-like regions to the stalked Pole of the mother cell. This area will remain at the site until the bud forms. This area (a region that looks like a centromere) is then carried at the flagellated pole, through the stalk, where the bud starts to form. The bud continues to grow in size until it is separated from its parent cell.
Based on previous studies, budding could be divided into different categories according to the number of cells that were produced during the budding process. These are:
- Multiplication by Budding – The daughter cell is larger than the mother, but it still grows to look like the mother/parent cells.
- Budding for Hyphal Branching – In this case, the budding process produces branches that are similar to those found in actinomycetes. This is common in Rhodomicrobium, Pedomicrobium, and other species.
- Budding for sporulation – Based on microscopic examinations, spores were found able to bud from the hyphae.
Budding in Hydra
- Hydra is a genus made up of freshwater organisms belonging to the phylum Cnidaria. They are closely related to jellyfish and other fresh-water organisms.
- Hydra, unlike many other organisms have attracted a lot of scientific attention due to their ability to regenerate and prevent them from ageing (from undergoing senescence). Budding is the main mode for reproduction in these organisms and results in the creation of a new individual who looks like the parent.
- Hydra vulgaris, Hydra oxycnida and Hydra oxycnida are some examples of hydra species.
- Research studies have led to a variety of findings about the budding process for hydra. Slowly budding hydras are smaller than the fast-growing hydras that can produce many buds at once.
- It was found that a high intake of food material can influence growth and reproduction. A lower feeding schedule leads to organismage.
- Budding begins with the evagination and endodermal layers of the ecto-endodermal cells at the lower portion of the parent Hydra. Eight (8) Hydra WNT genes were identified by molecular analysis at the tip.
- Eight genes are present at the tip, but only one (Hvwnt2) can be specific to the bud.
- The epithelial cells in the bud are transported from the parent body to the tip. They contribute to the bud’s growth and size. The bud will develop within two to three days depending on the species and the environmental conditions before being separated from its parent body by a contracting band.
- The contracting ring is located between the parent hydra’s body wall and the food of bud. It gradually contracts and cuts between them, thereby releasing the newly formed hydra.
- One parent might produce multiple buds at once. However, their sizes tend to differ with some larger than others.
- When they mature, larger buds produce new buds more quickly than smaller buds.
- Hydra will not produce new buds if they are starved for more than 6 days.
- Hydra cell division is crucial for budding. These cells are not considered waste because they are constantly producing new cells in large numbers. They are instead transported to the budding area where they help to grow the bud.
- According to a variety of studies, up to 85 percent of newly formed structural cell structures are transported into the budding area. By inhibiting cell growth, budding can be significantly slowed down or even stopped entirely.
Budding in Plants
- Plants are multicellular eukaryotes, which are primarily photosynthetic. They are the primary producers of the kingdom Plantae, which includes some bacteria, algae and moss. Plants produce sexually, just like many other organisms. This is done through gamete-fusion (in flowering plants).
- Some plants can reproduce sexually, while others alternate between sexual and asexual reproduction. Examples of asexual reproduction in plants include budding and apomixis.
- The scion is a plant name for the bud. It is used mainly in situations where the farmer or propagator desires certain characteristics above the ground (eg fruits, etc).
- A scion can be described as a single bud, not a stem/twig.
- A budding knife is used to cut a bud from a budstick in horticulture. To remove a bud from a plant’s stem, cut the stem using a budding knife. This is about a half inch from the base to about half an inch above it. This is where it is best to cut the wood that is attached to the bud. To prevent drying, the bud must be immediately inserted into understock.
- The understock is prepared by making a T-cut on the stem/branch where the bud will be placed. Once the bark is removed, place the bud under it and wrap it so that it stays in place.
- In about one week or ten days, the stem and the bud will join.
- Budding in plants is different from other organisms. It involves taking a bud from one plant, and then inserting it onto another. A bud can be created on any plant stem to achieve desired characteristics.
Advantages of Budding
- Budding, a quicker and more effective method of grafting in plants, allows the propagator to transfer the desired characteristics of the buds onto the stems of another plant.
- This method of reproduction is used today to produce fruit trees, roses, and other ornamental trees. This method has the greatest advantage in plants because it allows specific buds to be transferred to stems that are already in good growing conditions. The stems can then continue growing.
- This method of reproduction is used by other organisms to produce offspring in large numbers. This method of reproduction allows the good genes of an organism to be passed on to the daughter cells.
Disadvantages of Budding
- Budding organisms are not capable of adapting to changes in their environment and are therefore at risk of disappearing.
- It is impossible to create new varieties of organisms with a different genetic makeup.
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