Original Research ARTICLE
Gibberellin Promotes Sweetpotato Root Vascular Lignification and Reduces Storage-root Formation
- 1Agricultural Research Organization (ARO), Israel
- 2Wageningen University & Research, Netherlands
- 3Tel Aviv University, Israel
- 4Shanghai Botanical Garden, China
- 5Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences (CAS), China
Sweetpotato yield depends on a change in the developmental fate of adventitious roots into storage-roots. The mechanisms underlying this developmental switch are still unclear. We examined the hypothesis claiming that regulation of root lignification determines storage-root formation. We show that application of the plant hormone gibberellin increased stem elongation and root gibberellin levels, while having inhibitory effects on root system parameters, decreasing lateral root number and length, and significantly reducing storage-root number and diameter. Furthermore, gibberellin enhanced root xylem development, caused increased lignin deposition and, at the same time, decreased root starch accumulation. In accordance with these developmental effects, gibberellin application upregulated expression levels of sweetpotato orthologues of Arabidopsis vascular development regulators (IbNA075, IbVND7 and IbSND2) and of lignin biosynthesis genes (IbPAL, IbC4H, Ib4CL, IbCCoAOMT, IbCAD), while downregulating starch biosynthesis genes (IbAGPase, IbGBSS) in the roots. Interestingly, gibberellin downregulated root expression levels of orthologues of the Arabidopsis BREVIPEDICELLUS transcription factor (IbKN2, IbKN3), regulator of meristem maintenance. The results substantiate our hypothesis and mark gibberellin as an important player in regulation of sweetpotato root development, suggesting that increased fiber formation and lignification inhibit storage-root formation and yield. Taken together, our findings provide insight into the mechanisms underlying sweetpotato storage-root formation and provide a valuable database of genes for further research.
Keywords: Gene Expression, Gibbeerellin, Lignin, root anatomy, Starch, Storage root, Sweet potato, Xylem, yield
Received: 10 Jun 2019;
Accepted: 23 Sep 2019.
Copyright: © 2019 Singh, Sergeeva, Ligterink, Aloni, Zemach, Doron-faigenboim, Yang, Zhang, Shabtai and Firon. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: PhD. Nurit Firon, Agricultural Research Organization (ARO), Rishon LeZion, Central District, Israel, Vcfiron@volcani.agri.gov.il