Deoxyribonucleotide dephosphorylation by VENOSA4 supports organellar genome replication in plants
The replication of the three genomes in plant cells during germination is a complex process, which requires a high degree of coordination between the genome-containing compartments: the nucleus, mitochondria, and chloroplasts. The first committed step for the de novo synthesis of deoxynucleoside triphosphates (dNTPs), the building blocks for DNA replication, occurs exclusively in the cytosol. A…
During germination, plant cells must replicate three distinct genomes housed within their nucleus, mitochondria, and chloroplasts. The creation of deoxynucleoside triphosphates (dNTPs), the foundational components for DNA replication, exclusively takes place in the cytosol. A primary question remains unanswered: how are sufficient dNTPs made available to the organelles?
In this research, scientists investigated a protein named VENOSA4 (VEN4), a dNTP triphosphohydrolase, and its role in this process within Arabidopsis thaliana. By employing isotope feeding and mass spectrometry analysis, they discovered that VEN4 efficiently transforms newly synthesized dNTPs into deoxynucleosides (dNs). When VEN4 is mutated, this conversion is inhibited, leading to significant reductions in both cpDNA and mtDNA levels. However, supplying exogenous dNs can partially compensate for this loss.
The researchers concluded that VEN4's catabolic activity for dNTPs is crucial as it ensures an adequate supply of dNs to the chloroplasts and mitochondria. These organelles can then salvage these precursors and convert them back into dNTPs, which are subsequently used for DNA synthesis. This intriguing process demonstrates a unique mechanism that allows for the strategic allocation of DNA precursors between cellular compartments via selective transport and metabolic trapping.
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