Title : SP5G-mediated repression of potato tuberization under heat stress integrates photoperiodic, circadian, and hormonal signals
Abstract:
Potato tubers are swollen underground stems that develop from the tips of stolons through a process known as tuberization. This developmental transition is positively regulated by SP6A, an FT-like mobile tuberigen produced in leaves and transported to stolons, whereas SP5G acts upstream as a photoperiod-responsive repressor that suppresses SP6A expression under non-inductive conditions. Heat stress is a major constraint on potato productivity, largely because it inhibits stolon development and tuberization, yet the molecular basis of this inhibition remains poorly understood. In this study, we investigated the role of SP5G and related regulatory pathways in the tuberization response to heat stress. CRISPR-generated SP5G knockout lines in an Andigena background were exposed to controlled heat stress under short-day conditions, and their responses were evaluated using physiological analyses and RNA-seq. SP5G knockout significantly accelerated tuberization under heat stress, resulting in earlier and increased tuber formation relative to wild-type plants. This phenotype was associated with elevated expression of auxin and Jasmonic-acid biosynthesis genes, genes related to stolon swelling and cell expansion, and enhanced expression of circadian regulators linked to tuberization. Together, these findings indicate that SP5G may have a broader role than previously recognized, by rewiring the heat-responsive network that involves hormones & signals to promote tuberization during heat stress. This work provides new insight into the molecular regulation of heat-sensitive tuberization and highlights potential targets for improving potato productivity under elevated temperatures.
