Evolutionary and structural aspects of Solanaceae RNases T2

Abstract

Plant RNases T2 are involved in several physiological and developmental processes, including inorganic phosphate starvation, senescence, wounding, defense against pathogens, and the self-incompatibility system. Solanaceae RNases form three main clades, one composed exclusively of S-RNases and two that include S-like RNases. We identified several positively selected amino acids located in highly flexible regions of these molecules, mainly close to the B1 and B2 substrate-binding sites in S-like RNases and the hypervariable regions of S-RNases. These differences between S- and S-like RNases in the flexibility of amino acids in substrate-binding regions are essential to understand the RNA-binding process. For example, in the S-like RNase NT, two positively selected amino acid residues (Tyr156 and Asn134) are located at the most flexible sites on the molecular surface. RNase NT is induced in response to tobacco mosaic virus infection; these sites may thus be regions of interaction with pathogen proteins or viral RNA. Differential selective pressures acting on plant ribonucleases have increased amino acid variability and, consequently, structural differences within and among S-like RNases and S-RNases that seem to be essential for these proteins play different functions.

Evolution and diversification of the O-methyltransferase (OMT) gene family in Solanaceae

“…Based on a preliminary phylogenetic analysis of OMT proteins for 23 Solanaceae species (Figure S2 and S3), we found that sequences from congeneric species overall clustered together, suggesting that the phylogenetic signal is generally constrained at the genus level. Recent studies analyzing the evolutive stories of other gene families in Solanaceae found a similar pattern (Pereira et al, 2022;Thompson et al, 2023). Thus, we only kept one representative species of each genus to better visualize the evolutionary history of the OMT gene family in Solanaceae.…”