Journal Article

<i>IbMADS1</i> (<i>Ipomoea batatas MADS-box 1</i> gene) is Involved in Tuberous Root Initiation in Sweet Potato (<i>Ipomoea batatas</i>)

Amy Tsu Ku, Yi-Shiuan Huang, Yu-Shu Wang, Daifu Ma and Kai-Wun Yeh

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 102, issue 1, pages 57-67
Published in print July 2008 | ISSN: 0305-7364
Published online May 2008 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcn067
IbMADS1 (Ipomoea batatas MADS-box 1 gene) is Involved in Tuberous Root Initiation in Sweet Potato (Ipomoea batatas)

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry

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Background and Aims

The tuberization mechanism of sweet potato (Ipomoea batatas) has long been studied using various approaches. Morphological data have revealed that the tuberizing events result from the activation of the cambium, followed by cell proliferation. However, uncertainties still remain regarding the regulators participating in this signal-transduction pathway. An attempt was made to characterize the role of one MADS-box transcription factor, which was preferentially expressed in sweet potato roots at the early tuberization stage.

Methods

A differential expression level of IbMADS1 (Ipomoea batatas MADS-box 1) was detected temporally and spatially in sweet potato tissues. IbMADS1 responses to tuberization-related hormones were assessed. In order to identify the evolutionary significance, the expression pattern of IbMADS1 was surveyed in two tuber-deficient Ipomoea relatives, I. leucantha and I. trifida, and compared with sweet potato. In functional analyses, potato (Solanum tuberosum) was employed as a heterologous model. The resulting tuber morphogenesis was examined anatomically in order to address the physiological function of IbMADS1, which should act similarly in sweet potato.

Key Results IbMADS1

was preferentially expressed as tuberous root development proceeded. Its expression was inducible by tuberization-related hormones, such as jasmonic acid and cytokinins. In situ hybridization data showed that IbMADS1 transcripts were specifically distributed around immature meristematic cells within the stele and lateral root primordia. Inter-species examination indicated that IbMADS1 expression was relatively active in sweet potato roots, but undetectable in tuber-deficient Ipomoea species. IbMADS1-transformed potatoes exhibited tuber morphogenesis in the fibrous roots. The partial swellings along fibrous roots were mainly due to anomalous proliferation and differentiation in the xylem.

Conclusions

Based on this study, it is proposed that IbMADS1 is an important integrator at the initiation of tuberization. As a result, the initiation and development of tuberous roots seems to be well regulated by a network involving a MADS-box gene in which such hormones as jasmonic acid and cytokinins may act as trigger factors.

Keywords: Ipomoea batatas; Ipomoea relatives; root; MADS-box; transcription factors; IbMADS1; tuberization; tuberous roots; sweet potato

Journal Article.  6454 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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