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Potato tubers arise from specialized branches or stolons, in contrast to storage cassava roots which derive from specific non-fibrous roots in the shrub. At the same time, tuber initiation depends on short-day activation of an FT-like protein produced in leaves, whereas cassava taproot formation occurs independently of any FT signal. Because of these differences, both storage organs have long been considered as developmentally unrelated, while we challenge that view.
Tuber swelling has been attributed to proliferation of unknown meristematic cells situated between the pith and cortex in the subapical stolon region, in contrast to cassava, where radial growth is clearly seen to be driven by vascular cambium secondary growth. Using ClearSee imaging, single-cell RNA sequencing, and in situ hybridization, we demonstrate that the
proliferating cells driving early tuber growth are likewise cambial cells. In potato, the cambium exhibits a bicollateral organization, and the storage parenchyma arises predominantly from the phloem lineage rather than from xylem-side derivatives, as observed in cassava. This lineage-specific acquisition of storage fate correlates, in potato tubers, with activation of gibberellin catabolism. We therefore propose that reduced GA levels play a central role in directing cambial derivatives toward sink establishment and amyloplast differentiation, thereby enabling the massive starch accumulation that defines storage parenchyma cells.
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