Non-S-ribonucleases (non-S-RNases) are class III T2 RNases expressed in the styles of species exhibiting S-RNase-based self-incompatibility (SI). So far, no role has been attributed to these RNases, which are not functional in the SI system. By combining RT-PCR, immunoblot and enzymatic activity approaches, Rojas et al. demonstrate that NnSR1 (Nicotiana non-S–RNase1) is induced in roots of Nicotiana alata subjected to phosphate deprivation, resembling the functionality of phylogenetically divergent class I and class II S-like RNases. NnSR1 appears to have regained ancestral functions of class III RNases related to strategies to cope with phosphate limitation and possibly with other environmental challenges.
