NITROPLAST – THE NEWLY DISCOVERED CELL ORGANELLE

Abstract

Cells are often depicted as tiny factories that take in raw materials and use them to produce what they need to survive. One
function long thought to have eluded eukaryotic cells is the ability to capture nitrogen gas (N₂) from the air and convert it
into essential amino acids. Until recently, this metabolic pathway was considered exclusive to bacteria. However, the
discovery of the first nitrogen-fixing organelle, the nitroplast, believed to have originated from the engulfment and evolution
of a bacterial cell, has prompted researchers to explore and engineer potential applications, particularly in enhancing plant
and crop growth. The nitroplast was first hypothesized when nitrogenase (nifH) genes from unicellular cyanobacteria
(UCYN-A) were detected in marine algal samples in the late 1990s. Subsequent studies demonstrated key organelle-like
traits such as protein import, synchronized division with host cells, and genome reduction, confirming its transition from
endosymbiont to organelle. The discovery provides insight into primary endosymbiosis processes and marks only the fourth
known case of organelle-level evolution. Ecologically, nitroplast-bearing algae significantly influence marine nitrogen and
carbon cycles, while biotechnologically, this finding opens avenues for engineering nitrogen-fixing crops, potentially
reducing dependence on synthetic fertilizers. This review summarizes current knowledge, evolutionary implications, and
the vast agricultural potential of this remarkable organelle.