Temporally Distinct Regulatory Pathways Coordinate Thermo-Responsive Storage Organ Formation in Potato

Tuberization, which is highly affected by environmental conditions, is an important developmental process in potatoes (Solanum tuberosum). Temperature is a major environmental factor affecting tuberization, with high temperatures suppressing tuber formation. A potato homolog of florigen FLOWERING LOCUS T, designated as SELF-PRUNING 6A (StSP6A), has been identified as responsible for determining tuber development at high temperatures. However, the temporal aspects of thermo-responsive tuberization remain elusive. For a deeper understanding of tuberization mechanisms at high temperatures, we performed time-course analyses during tuber development under various temperature regimes. Tuber formation was initially delayed by increased temperatures at the start of tuberization, but transcript levels of StSP6A did not change. Experiments using transgenic plants overexpressing StSP6A under the control of constitutive promoter showed that post-transcriptional regulation plays a major role at the early stage, while transcriptional regulation is an important late-stage factor, suppressing StSP6A at high temperatures. Transcriptome analyses led to the identification of potential molecular factors that may be involved in thermo-responsive tuber development at different stages of tuberization. Our work shows that potato has temporally distinct molecular mechanisms that finely control tuber development at high temperatures. Therefore, time-course analysis would be necessary to understand temperature-dependent tuberization processes.