Can the newly discovered organelle help engineer plants to fix nitrogen?
- May 6, 2024
- Posted by: OptimizeIAS Team
- Category: DPN Topics
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Can the newly discovered organelle help engineer plants to fix nitrogen?
Sub: Sci
Sec: SciTech
Endosymbiotic Theory:
- Initially posited by Charles Darwin in the 19th century, the theory of natural selection explains how species adapt to their environment.
- Contrary to the Neo-Darwinist focus on random genetic mutations, Lynn Margulis proposed the endosymbiotic theory suggesting that organelles such as mitochondria and chloroplasts (the sites of cellular respiration and photosynthesis) originated from free-living bacteria ingested by other cells. Despite initial resistance and rejection by 15 journals, her theory gained acceptance following publication in 1967.
Recent Discoveries in Nitrogen Fixation:
- Nitrogen, crucial for DNA and proteins, is mostly inert in the atmosphere, necessitating biological fixation into ammonia by certain bacteria and archaea. This process is vital for making nitrogen accessible to plants.
- Unlike many free-living nitrogen-fixing bacteria, legumes, a class of plants in the family Fabaceae, bear the nitrogen-fixing bacteria in their root nodules.
- Ammonia is converted to nitrites and nitrates (nitrification) and then back into atmospheric nitrogen (denitrification) with the help of bacteria to complete the cycle.
- In marine environments, like on Earth, bacteria and archaea are also involved in ammonification, nitrification, and denitrification. Beyond mitochondria and chloroplasts, the current discovery extends the earlier reports of a nitrogen-fixing cyanobacterium in marine algae and establishes it as a new organelle. The new organelle ‘nitroplast’ co-evolved with its host cell.
- Jonathan Zehr and Kyoko Hagino’s research established the symbiotic relationship between the marine algae Braarudosphaera bigelowii and the cyanobacterium Candidatus Atelocyanobacterium thalassa or UCYN-A (capable of fixing nitrogen).
- Unlike mitochondria and chloroplast endosymbiosis, which happened nearly two billion years back, nitroplast’s evolution as an organelle is relatively recent (about 100 million years).
Criteria for Organelle Status:
- Nitroplast satisfies essential criteria for being considered an organelle, such as integration into the host cell’s function and architecture, protein import from the host, synchronization with host cell growth, and inheritance during cell division.
- Genomic and Functional Adaptation: The transformation of symbionts into organelles involves significant genetic reduction and reliance on host cell proteins, with nitroplasts exhibiting these characteristics.
Significance of the discovery:
- The industrial synthesis of ammonia via the Haber-Bosch process has significantly boosted agriculture but also led to environmental issues. The discovery of nitroplasts may lead to sustainable agricultural practices by facilitating biological nitrogen fixation in plants.
- Potential applications include engineering host cells and nitroplasts with minimal genomes for efficient growth and nitrogen fixation, and introducing nitroplasts into plant cells to directly fix nitrogen. These approaches, while promising, pose significant scientific challenges and are currently theoretical.
- The extension of the endosymbiotic theory to include nitrogen-fixing organelles represents a significant leap in understanding cellular evolution and symbiosis. This advancement not only deepens our comprehension of biological complexity but also holds transformative potential for agriculture, promising a future of environmentally friendly and sustainable farming practices.
Source: TH