About 1.5 billion years ago, an ancient cyanobacterium took up residence within a eukaryotic cell, forming a new organelle: the chloroplast, which is indispensable for photosynthesis and, consequently, life on Earth. But how did this organelle evolve within cells and continue to function despite genetic losses over time?
In a recent publication in Proceedings of the National Academy of Sciences (PNAS), Dr. Laurence Drouard’s team uncovered a fascinating mechanism in Selaginella, a genus of primitive vascular plants. These plants have lost many of the transfer RNA (tRNA) genes within their chloroplasts, even though these tRNAs are essential for synthesizing the proteins needed for photosynthesis. So, how do they still manage to produce the required proteins?
The study reveals that some of these plants compensate for this loss by importing tRNAs from the cell nucleus into the chloroplasts. These tRNAs, produced elsewhere in the cell, are actively imported into the chloroplasts to ensure protein translation. This innovative strategy allows Selaginella to maintain its photosynthetic capacity despite a major reduction in chloroplast tRNA genes.
This process relies on the transfer of tRNAs from the nucleus to the chloroplast, a phenomenon previously observed only in mitochondria. This mechanism of importation and gene transfer highlights the complexity and flexibility of evolutionary adaptations that enable plants to sustain essential functions despite gene losses over their evolutionary history.
These findings reveal a unique molecular innovation, shedding new light on how plants compensate for genetic losses in their organelles to maintain essential vital functions.
