PiPho85, a cyclin-dependent kinase of Piriformospora indica rescue colonized maize plants grown under salt stress.

We identified, isolated, and functionally characterized a cyclin-dependent kinase (CDK), PiPho85, from Piriformospora indica. The identified PiPho85 contains TY, PSTAIRE, protein kinase domain, and an ATP binding site which is highly conserved among the Pho85/CDK5 family protein specific for Saccharomyces cerevisiae. In a S. cerevisiae mutant strain (Δpho85), PiPho85 could regulate the acid phosphatase activity, restore the normal phenotype, confer salt- and drug-tolerance, and enable utilization of non-fermentable sugars. This suggests that PiPho85 complements the Pho85 function. The PiPho85 knock down (Kd) strain was generated by RNA interference (RNAi) and named as Kd-PiPho85-P. indica. The Kd strain was found susceptible to salt, drug and osmolarity stress and showed morphological abnormalities, abnormal-sized hyphae with large knot-like structure. This suggests that PiPho85 plays a regularity role in the physiology of P. indica. Further, Kd-PiPho85 -P. indica colonized plants were found to be susceptible to salt stress and showed less growth than that of wild type (WT) P. indica colonized plants. This suggests that PiPho85 plays a crucial role in conferring resistance to WT P. indica colonized plants during salt stress.