Conservation of redox-sensitive cysteines in SAL1 orthologs in plants. The Cys119 involved in dimerization of AtSAL1 is moderately conserved in eudicots and non-Poaceae monocot plants but is absent in other lineages. The intramolecular disulfide pair Cys167–Cys190 is invariant across bryophytes, lycophytes, primitive angiosperm, eudicots, and non-Poaceae monocots. Cys190 is C-terminally shifted by seven amino acids in Poaceae monocot plants. Additionally, another cysteine is strongly conserved in the Poaceae family of monocots (Cys221 in OsSAL1; Fig. 7). In contrast to plant SAL1 orthologs (green), the fungal SAL1 ortholog in Saccharomyces cerevisiae HAL2 (blue) lacks Cys119 and Cys190.