Insights into regulation of C2 and C4 photosynthesis in two independent C4 lineages of Chenopodiaceae using RNA-Seq

Amaranthaceae s.l. (incl. Chenopodiaceae) show an immense diversity of the C4 syndrome. More than 15 independent origins of C4 photosynthesis and the largest number of C4 species in the eudicots signify the importance of this angiosperm lineage. Thus far, only few of these 15 C4 origins were intensely studied, though. One element that combines all C4 species is high expression of genes encoding for key enzymes of the C4 cycle, for example carbonic anhydrase, NADP-malic enzyme, and phosphoenolpyruvate carboxylase. Only recently, investigations started to look at the regulation leading to high expression of these C4 genes. Here, we conduct RNA-Seq followed by comparative transcriptome analysis of three species from Camphorosmeae with different photosynthetic types: Threlkeldia diffusa (C3), Sedobassia sedoides (C2), and Bassia prostrata (C4). By combining our newly generated data from these three Camphorosmeae species with a publicly available data set from five species of the sister lineage Salsoleae, which also comprises C3, C2, and C4 species, we investigate whether the independent C4 lineages of these two groups share common changes in transcript abundance compared with their respective closely related C3 lineages with focus on transcript abundance of trans-elements. Furthermore, we look into commonalities in transcript abundance between the two independent C2 species Salsola divaricata and Sedobassia sedoides.