Table III. Interdependence of the occurrence of SDH5 to SDH8 and the number of membrane-spanning helices in SDH3 and SDH4.
Searches for homologs were performed by BLASTp using the amino acid sequences of mature SDH3 to SDH8 from Arabidopsis (Supplemental Fig. S4). Databases used were the Charophyta protein database (https://giavap-genomes.ibpc.fr/cgi-bin/AlgoBLAST/algoBlast.php) and the plant genome database (https://phytozome.jgi.doe.gov/pz/portal.html). Searches for homologs in M. viride and N. hyalina were carried out by tBLASTn using EST databases at the NCBI (http://blast.ncbi.nlm.nih.gov/Blast.cgi). Homologs of SDH8 in monocots were identified using the sequence of SDH8 from rice (UniProt identifier Q0DF13). + indicates the occurrence of homologs (for details, see Supplemental Table S1; Supplemental Fig. S11), and − indicates the absence of homologs. Accession numbers of homologs are given in Supplemental Figure S11.
| Organism | Clade | SDH5a | SDH6a | SDH7a | SDH8a | SDH3 (No. of Transmembrane Helices)b | SDH4 (No. of Transmembrane Helices)b |
|---|---|---|---|---|---|---|---|
| Escherichia coli | Prokaryota | − | − | − | − | P69054 (3) | P0AC44 (3) |
| Mesostigma viride | Charophyta | + | + | − | − | G8DKD7 (3) | G8DKD0 (2) |
| Klebsormidium flaccidum | Charophyta | + | + | − | − | AJF36733.1 (3) | AJF36745.1 (2) |
| Chlorokybus atmophyticus | Charophyta | + | + | − | − | YP_001315099.1 (3) | YP_001315098.1(2) |
| Nitella hyalina | Charophyta | + | + | + | − | YP_006073043.1 (3) | YP_006073042.1 (2) |
| Physcomitrella patens | Bryophyta | + | + | + | − | Q1XGB9 (3) | Q1XGC0 (2) |
| Marchantia polymorpha | Marchantiophyta | + | + | + | − | P35721 (3) | NP_054431.1 (2) |
| Amborella trichopoda | Basal angiosperm | + | + | + | − | V9VIA6 (2) | V9VF77 (2) |
| Oryza sativa | Monocot | + | + | + | + | Q6ZH92 (1) | Q942X4 (2) |
| Zea mays | Monocot | + | + | + | + | A0A096QEW9 (1) | C4J8S0 (2) |
| Medicago truncatula | Dicot | + | + | + | − | G7JDI5 (2) | G7J5Z9 (2) |
| Arabidopsis thaliana | Dicot | + | + | + | + | A8MSF5 (2) | Q941A0 (1) |
Occurrence of SDH5 to SDH8 subunits in Streptophyta (land plants and Charophyta) and in E. coli. bUniProt identifiers (if UniProt identifiers are not available, alternative accessions are given, such as GenBank identifier [K. flaccidum] and NCBI reference sequence [C. atmophyticus, N. hyalina, and M. polymorpha]). The number of transmembrane helices in SDH3 and SDH4 was determined using the TMHMM server version 2.0 (Supplemental Figs. S5 and S10). For details, see Supplemental Figure S12. The threshold for helix prediction was set to 0.3.