Physiological and Molecular Responses of Projected Future Temperatures on Potato Tuberization

Potato (Solanum tuberosum L.) is one of the most important food crops globally and is especially vulnerable to heat stress. Significant knowledge gaps remain however, in our understanding of the developmental mechanisms associated with tuber responses to heat stress. This study uses whole-plant physiology, transcriptomics, and hormone profiling to gain insights into the mechanisms associated with heat stress impacts on potato tuber development. When plants were grown in projected future temperature conditions, levels of abscisic acid (ABA) were significantly decreased in leaf and tuber tissues while rates of leaf carbon assimilation and stomatal conductance were not significantly affected. While plants grown in elevated temperature conditions initiated more tubers on average per plant, there was a significant decrease (66%) in mature tubers at final harvest. We hypothesize that reduced tuber yields at elevated temperatures are not due to reductions in tuber initiation, but due to impaired tuber filling. Transcriptomic analysis found significant changes in transcript expression for genes related to response to ABA, heat and auxin biosynthetic process. The known tuberization repressor genes SELF PRUNING 5G (StSP5G) and CONSTANS-LIKE1 (StCOL1) were found to be differentially expressed in tubers grown in elevated temperatures. IDENTITY OF TUBER 1 (StIT1) and TIMING OF CAB EXPRESSION 1 (StTOC1) are other known tuberization genes that displayed distinct expression patterns in elevated versus ambient temperatures but were not differentially expressed. This work highlights potential gene targets and key developmental stages associated with tuberization to development more heat tolerant potatoes.