Molecular Mechanisms of Storage Root Development in Sweet Potato

Storage root formation in sweet potato is a highly orchestrated process that transforms fine adventitious roots into enlarged, starch‐rich organs. This transition is governed by the initiation of a secondary meristem (cambium) that drives radial thickening and the deposition of storage compounds. At the molecular level, a shift in carbon flux away from phenylpropanoid pathways towards starch biosynthesis is critical: genes encoding enzymes for lignin synthesis are downregulated, while those for ADP-glucose pyrophosphorylase and starch branching exhibit marked upregulation. Phytohormones such as auxin, cytokinin, jasmonate and gibberellin coordinate cambial activity and cell proliferation, with specific transcription factors (including members of the KNOX, NAC and ARF families) directing developmental fate. Post-transcriptional mechanisms and reactive oxygen species signalling further fine-tune gene expression, while antioxidative enzyme systems safeguard the nascent storage tissue. Integrative omics approaches—combining transcriptomics, proteomics and metabolomics—have begun to reveal regulatory networks that underpin the initiation, expansion and maturation of storage roots, offering targets for breeding and biotechnological improvement of yield and quality.

Research from Nature Portfolio

Recent studies have demonstrated that altering phenylpropanoid metabolism can profoundly affect early storage root development. Heterologous expression of a maize anthocyanin regulator in sweet potato enhanced lignin biosynthesis in developing roots, leading to increased vascular cell lignification, reduced starch accumulation and diminished storage root size. This work provides direct evidence that a balance between lignification and starch deposition determines root fate.

Comparative analyses of cultivars with differing post-harvest storability have also highlighted the role of reactive oxygen species (ROS) scavenging in storage root quality. Cultivars that maintain higher activities and expression levels of antioxidative enzymes—such as superoxide dismutase, catalase and peroxidases—exhibit lower ROS accumulation, correlating with improved storage tolerance and retention of starch reserves.

Molecular Mechanisms of Storage Root Development in Sweet Potato publication trend

The graph below shows the total number of articles in molecular mechanisms of storage root development in sweet potato across all publications each year (not limited to Nature Index journals).

Technical terms

Cambium: A lateral meristem that generates secondary xylem and phloem, crucial for root thickening.

Phenylpropanoid Metabolism: A biosynthetic pathway producing lignin and other phenolic compounds that can compete with starch biosynthesis for carbon.

Lignification: The process of depositing lignin in cell walls, strengthening vascular tissue but limiting storage parenchyma expansion.

Reactive Oxygen Species (ROS): Highly reactive molecules derived from oxygen that act as signalling agents but can cause cellular damage if not scavenged.

Superoxide Dismutase (SOD): An enzyme that converts superoxide radicals to hydrogen peroxide, part of the antioxidative defence.

ADP-Glucose Pyrophosphorylase: A key enzyme in starch biosynthesis catalysing the formation of ADP-glucose, the precursor for polymerisation.

Transcription Factor (TF): A protein that binds DNA regulatory regions to modulate gene expression during development.

Omics: Comprehensive approaches (e.g., genomics, transcriptomics, proteomics, metabolomics) used to analyse entire sets of biological molecules.

References

1. Altered Phenylpropanoid Metabolism in the Maize Lc-Expressed Sweet Potato (Ipomoea batatas) Affects Storage Root Development. Scientific Reports (2016).
2. Gibberellin Promotes Sweetpotato Root Vascular Lignification and Reduces Storage-Root Formation. Frontiers in Plant Science (2019).
3. Transcriptional profiling of sweetpotato (Ipomoea batatas) roots indicates down-regulation of lignin biosynthesis and up-regulation of starch biosynthesis at an early stage of storage root formation. BMC Genomics (2013).
4. RNA-Seq and iTRAQ reveal multiple pathways involved in storage root formation and development in sweet potato (Ipomoea batatas L.). BMC Plant Biology (2019).
5. Antioxidative capacity is highly associated with the storage property of tuberous roots in different sweetpotato cultivars. Scientific Reports (2019).