Symplasmic phloem unloading and radial post-phloem transport via vascular rays in tuberous roots of Manihot esculenta

Mehdi R, Lamm C, Bodampalli Anjanappa R, Müdsam C, Saeed M, Klima J, Kraner M, Ludewig F, Knoblauch M, Gruissem W, Sonnewald U, Zierer W (2019)

Publication Type: Journal article

Publication year: 2019

Journal

Book Volume: 70

Pages Range: 5559-5573

Journal Issue: 20

DOI: 10.1093/jxb/erz297

Abstract

Cassava (Manihot esculenta) is one of the most important staple food crops worldwide. Its starchy tuberous roots supply over 800 million people with carbohydrates. Yet, surprisingly little is known about the processes involved in filling of those vital storage organs. A better understanding of cassava carbohydrate allocation and starch storage is key to improving storage root yield. Here, we studied cassava morphology and phloem sap flow from source to sink using transgenic pAtSUC2::GFP plants, the phloem tracers esculin and 5(6)-carboxyfluorescein diacetate, as well as several staining techniques. We show that cassava performs apoplasmic phloem loading in source leaves and symplasmic unloading into phloem parenchyma cells of tuberous roots. We demonstrate that vascular rays play an important role in radial transport from the phloem to xylem parenchyma cells in tuberous roots. Furthermore, enzymatic and proteomic measurements of storage root tissues confirmed high abundance and activity of enzymes involved in the sucrose synthase-mediated pathway and indicated that starch is stored most efficiently in the outer xylem layers of tuberous roots. Our findings form the basis for biotechnological approaches aimed at improved phloem loading and enhanced carbohydrate allocation and storage in order to increase tuberous root yield of cassava.

Authors with CRIS profile

Involved external institutions

Eidgenössische Technische Hochschule Zürich (ETHZ) / Swiss Federal Institute of Technology in Zurich Switzerland (CH) Washington State University (WSU) United States (USA) (US)

How to cite

APA:

Mehdi, R., Lamm, C., Bodampalli Anjanappa, R., Müdsam, C., Saeed, M., Klima, J.,... Zierer, W. (2019). Symplasmic phloem unloading and radial post-phloem transport via vascular rays in tuberous roots of Manihot esculenta. Journal of Experimental Botany, 70(20), 5559-5573. https://doi.org/10.1093/jxb/erz297

MLA:

Mehdi, Rabih, et al. "Symplasmic phloem unloading and radial post-phloem transport via vascular rays in tuberous roots of Manihot esculenta." Journal of Experimental Botany 70.20 (2019): 5559-5573.

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