Effect of a Radical Mutation in Plastidic Starch Phosphorylase PHO1a on Potato Growth and Cold Stress Response

The plant response to stresses includes changes in starch metabolism regulated by a complex catalytic network, in which plastidic starch phosphorylase PHO1a is one of the key players. In this study, we used the CRISPR-Cas9 system to edit the PHO1a gene in four potato (Solanum tuberosum L.) cultivars, which resulted in the introduction of a radical mutation, G261V, into the PHO1a functional domain. The mutants had altered morphology and differed from wild-type plants in starch content in the roots and leaves. Exposure to cold stress revealed the differential response of parental and transgenic plants in terms of starch content and the expression of genes coding for beta-amylases, amylase inhibitors, and stress-responsive MADS-domain transcription factors. These results suggest that the G261V mutation causes changes in the functional activity of PHO1a, which in turn affect the coordinated operation of starch catabolism enzymes both under normal and cold stress conditions, possibly through differential expression of MADS-domain transcription factors. Our results highlight a critical regulatory role of PHO1a in starch metabolism, root and shoot development, and stress response in potatoes.