Chromosomes are lengthy DNA-carrying structures found in the center of the cell nucleus. DNA is a fundamental biomolecular component in most higher organisms as it is comprised of genes.
Basically, chromosomes refer to the wounded DNA treads to make them compact enough to fit inside the nucleus. And they serve several functions from carrying genetic information to protein synthesis.
Here we will discuss the chromosome function in plant cells. Plant chromosomes:
Even though both plant and animal cells are eukaryotic organisms they have different features. This means that they have different genetic requirements. Hence their chromosomal functions apart from the essentials also have some differences.
Chromosome function in plant cells:
Carrier of Mendelian factors:
The main chromosomal function is to carry information from one generation of the cell to the next in the form of genes. This included information about the features of the organism- length, height, colours they show or express etc. These features that are genetically passable from one generation to the next are called Mendelian factors.
Influencing DNA accessibility:
The accessibility of DNA is fine-tuned by chromatin structure, which affects gene expression and defines cell developmental and metabolic identity, as well as plant growth and development. The platform for recruiting protein complexes that act on chromatin is made up of nucleosomes, which have roughly 150 base pairs of DNA wrapped around each octamer of histones H2A, H2B, H3, and H4, as well as a linker histone H1. DNA can be methylated, and histones can be subjected to lysine or arginine methylation, lysine acetylation, lysine ubiquitination, or serine phosphorylation, among other post-translational changes.
Influence on gene expression:
The expression of metabolic genes is modulated by chromatin structure, which impacts metabolic states. Despite the importance of chromatin structure for transcription, evidence of chromatin modifiers directly controlling metabolic genes was just recently discovered. SDG8, the HKMT that catalyses gene-body H3K36me3, for example, directly targets genes involved in photosynthesis, nutrition and energy metabolism, as well as genes that respond to carbon or light therapy.
Image: Wikipedia
Gene control:
Though not a lot of research has been done on this topic, the function of chromosomes in gene control in plants cannot be denied as widely seen in animal and yeast cells. Chromatin modifying complexes such as – histone acetyltransferases, histone deacetylases and SWI/SNF complexes have significant roles in plant gene control.
Determining the sex of the plant:
Like all organisms, higher plants have male and female parts, especially in the floral parts that act as the reproductive parts. The sex chromosomes of most higher determine their gender. Plants, unlike most animals, can be either male or female, or even have both features at the same time.
Image: Wikipedia
However, a lot of plants to avoid being self-pollinated make sure that if the pollen is from a flower from the same plant become non-viable, or the male and female flowers mature at different times. Such features are determined by the adaptations of these plants that have been imprinted into their chromosomal information.
Carrying forward useful adaptations:
In the case of carnivorous plants that grow in soil that have very low nitrogen content, the plants have changed and modified their leaves to be able to photosynthesize and also catch live organisms to fulfil their nutrient content. Since they cannot absorb any such nutrients from their environment they have underdeveloped roots. This is a result of evolution over centuries that has been embedded into the chromosome with every single step. Since this is how they are genetically constituted they do not produce the required features to grow in a nutrient-rich media where they will probably end up dead.
Protein synthesis:
Chromosomes hold genes that express the proteins that are required by an organism to function properly including enzymes and hormones. Plants are not an exception in this are very dependent on the hormones produced in them to grow and function to their fullest.
Chromosome structure:
Every chromosome has something called a centromere also called the primary constriction- a small fixed part of the chromosome where the spindles attach to the chromosome during mitosis or meiosis. The centromere ensures that the sister cells have equal chromosomal distribution after division. They also have a telomere made up of tandem repetitions of short DNA fragments.
In mitotic metaphase, each chromosome has two symmetrical structures known as chromatids or sister chromatids. A single DNA molecule constitutes each chromatid. The centromere links sister chromatids together. The centromere is where spindle fibres connect during cell division. Varied chromosomes have different numbers and locations for the centromere.
Image: Wikipedia
Chromosomes also have secondary constrictions in addition to the centromere. Because there is only bending at the centromere during anaphase, secondary constrictions can be observed (primary constriction). The nucleolar organizer is a secondary constriction that contains genes that generate nucleoli.
The chromosome is divided into two sections by the centromere; usually where one arm is shorter than another. The shorter arm is called the ‘p’ arm, while the longer arm is called the ‘q’ arm. A disc-shaped kinetochore is found in the centromere and contains a unique DNA sequence as well as special proteins attached to it. The kinetochore is where tubulin proteins are polymerized and microtubules are assembled.
Chromatin is a component of the chromosome. DNA, RNA, and proteins make up chromatin. Chromosomes are evident in the nucleoplasm as thin chromatin threads during interphase. The chromatin fibres condense during cell division, revealing chromosomes with different characteristics. Heterochromatin is the darkly pigmented, compacted portion of chromatin. It comprises tightly packed and genetically inactive DNA. Euchromatin is the light-stained, dispersed portion of chromatin.
Chromatin contains genetically active and loosely packed DNA. During prophase, the chromosomal material appears as thin filaments called chromonemata. During interphase, chromomeres, which are bead-like structures made up of chromatin material, can be detected. Chromatin with chromomere resembles a beaded necklace.
The chromosome terminal is called the telomere. The telomere is polar by nature to avoid the ligation of the chromosomal segments.
Also Read:
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- Is primary transport active
- Is cytosine a pyrimidine
- Parenchyma cells function
- Is chromosome a cell
- Food vacuole in fungi
- Do eukaryotes have endoplasmic reticulum
- Do animal cells have flagella
- Transplanting plants examples
- Femur anatomy
I am Trisha Dey, a postgraduate in Bioinformatics. I pursued my graduate degree in Biochemistry. I love reading .I also have a passion for learning new languages.
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