Antifreeze Protein Gene Products Inhibit Ice Recrystallisation, Attenuate Ice Nucleation, and Reduce Immune Response.

Antifreeze proteins (AFPs) from the model crop, , allow freeze survival and attenuate pathogen-mediated ice nucleation. Intriguingly, AFP genes encode two proteins, an autonomous AFP and a leucine-rich repeat (LRR). We present structural models which indicate that ice-binding motifs on the ~13 kDa AFPs can "spoil" nucleating arrays on the ~120 kDa bacterial ice nucleating proteins used to form ice at high sub-zero temperatures. These models are consistent with the experimentally demonstrated decreases in ice nucleating activity by lysates from wildtype compared to transgenic lines. Additionally, the expression of LRRs in transgenic inhibited an immune response to pathogen flagella peptides (flg22). Structural models suggested that this was due to the affinity of the LRR domains to flg22. Overall, it is remarkable that the genes play multiple distinctive roles in connecting freeze survival and anti-pathogenic systems via their encoded proteins' ability to adsorb to ice as well as to attenuate bacterial ice nucleation and the host immune response.