**3. Discussion**

Green algae form two discrete clades, chlorophytes and charophytes [65]. Chlorophytes are morphologically diverse, cosmopolitan and contain the majority of green algae. Chlorophyte chondriomes are nearly as diverse as their morphologies, ranging from 15,500–66,000 bp with few introns and highly variable intergenic spaces, gene content, and gene synteny [60,66–75]. The knowledge of transcription and post-transcriptional processing events in chlorophytic mitochondria is limited to the model system *C. reinhardtii*, where mature mRNAs have no 5- UTR and relatively short 3 termini that may be polycytidylated. *C. reinhardtii* has a very small linear chondriome that is not representative of the majority of algae, and it is unknown if the post-transcriptional processing characteristics are hallmarks of its reduced chondriome or traits conserved among chlorophytes. Charophytes diverged from chlorophytes a billion or more years ago and have biochemical and morphological synapomorphies shared only with embryophytes [76]. The relatively few extant species belong to six monophyletic clades and are the closest living algal relatives of land plants [63,77]. The chondriomes of charophytes range widely from 56,500 bp to >201,000 bp, with highly variable gene order, density, and intron placement [63].
