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

Mehdi, Rabih; Lamm, Christian E.; Anjanappa, Ravi B.; Müdsam, Christina; Saeed, Muhammad; Klima, Janine; Kraner, Max; Ludewig, Frank; Knoblauch, Michael; Gruissem, Wilhelm; Sonnewald, Uwe; Zierer, Wolfgang

doi:10.1093/jxb/erz297

Cited by 43 publications

(79 citation statements)

References 80 publications

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“…These results suggested a shift in sugar transport from an apoplasmic mode in fibrous roots to a symplasmic mode in storage roots. This was subsequently confirmed in cassava plants expressing phloem‐specific green fluorescent protein and by detailed histological analysis using apoplasmic and symplasmic tracer molecules (Mehdi et al ., 2019). In addition, many transcription factors were differentially expressed between fibrous roots and during storage root development.…”

Section: Learning From Genetic Diversity Of Cassavamentioning

confidence: 99%

“…Currently, we are focusing on the identification and testing of additional storage root promoters, as well as phloem‐ and cambium‐specific promoters. In the case of phloem‐specific expression, the applicability of the Arabidopsis SUCROSE TRANSPORTER 2 ( AtSUC2 ) promoter could be confirmed (Mehdi et al ., 2019).…”

Section: Considerations Prior To Engineering Cassava Plants For Highementioning

confidence: 99%

“…Based on our previous work, we have now a basic understanding of cassava source and sink metabolism. Cassava performs C3 photosynthesis (Arrivault et al ., 2019) and leaf photoassimilates are loaded apoplasmically into the phloem (Mehdi et al ., 2019). Nodal‐derived fibrous roots, emerging on planted cassava stem pieces, develop into storage roots by secondary growth.…”

Section: Introductionmentioning

confidence: 99%

“…Longitudinal, cambium‐derived vascular ray cells bridge the two cell types ensuring exchange of water, nutrients, and carbohydrates (Figure 1). Unloading of the photoasimilates in storage roots follows a symplasmic route to the storage parenchyma cells and is facilitated by vascular rays (Mehdi et al ., 2019). Alternating ray initial cells and fusiform initial cells in the vascular cambium give rise to the vascular ray cells and xylem/phloem cells, respectively.…”

Section: Introductionmentioning

confidence: 99%

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The Cassava Source–Sink project: opportunities and challenges for crop improvement by metabolic engineering

et al. 2020

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Summary Cassava (Manihot esculenta Crantz) is one of the important staple foods in Sub‐Saharan Africa. It produces starchy storage roots that provide food and income for several hundred million people, mainly in tropical agriculture zones. Increasing cassava storage root and starch yield is one of the major breeding targets with respect to securing the future food supply for the growing population of Sub‐Saharan Africa. The Cassava Source–Sink (CASS) project aims to increase cassava storage root and starch yield by strategically integrating approaches from different disciplines. We present our perspective and progress on cassava as an applied research organism and provide insight into the CASS strategy, which can serve as a blueprint for the improvement of other root and tuber crops. Extensive profiling of different field‐grown cassava genotypes generates information for leaf, phloem, and root metabolic and physiological processes that are relevant for biotechnological improvements. A multi‐national pipeline for genetic engineering of cassava plants covers all steps from gene discovery, cloning, transformation, molecular and biochemical characterization, confined field trials, and phenotyping of the seasonal dynamics of shoot traits under field conditions. Together, the CASS project generates comprehensive data to facilitate conventional breeding strategies for high‐yielding cassava genotypes. It also builds the foundation for genome‐scale metabolic modelling aiming to predict targets and bottlenecks in metabolic pathways. This information is used to engineer cassava genotypes with improved source–sink relations and increased yield potential.

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Section: Learning From Genetic Diversity Of Cassavamentioning

confidence: 99%

Section: Considerations Prior To Engineering Cassava Plants For Highementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Cassava Source–Sink project: opportunities and challenges for crop improvement by metabolic engineering

et al. 2020

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“…Cross-sections of cassava, sweet potato, and radish were stained with toluidine blue. Images for sugar beet and cassava were adapted from Barba-Espin et al 2018and Mehdi et al (2019), respectively, which are distributed under the Creative Commons Attribution 4.0 International Licenses (https://creativecommons.org/licenses/by/4.0/). Arrow heads point to cambia.…”

Section: Environmental and Internal Signals That Induce Storage Root mentioning

confidence: 99%

Gene Regulatory Network Guided Investigations and Engineering of Storage Root Development in Root Crops

et al. 2020

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The plasticity of plant development relies on its ability to balance growth and stress resistance. To do this, plants have established highly coordinated gene regulatory networks (GRNs) of the transcription factors and signaling components involved in developmental processes and stress responses. In root crops, yields of storage roots are mainly determined by secondary growth driven by the vascular cambium. In relation to this, a dynamic yet intricate GRN should operate in the vascular cambium, in coordination with environmental changes. Despite the significance of root crops as food sources, GRNs wired to mediate secondary growth in the storage root have just begun to emerge, specifically with the study of the radish. Gene expression data available with regard to other important root crops are not detailed enough for us directly to infer underlying molecular mechanisms. Thus, in this review, we provide a general overview of the regulatory programs governing the development and functions of the vascular cambium in model systems, and the role of the vascular cambium on the growth and yield potential of the storage roots in root crops. We then undertake a reanalysis of recent gene expression data generated for major root crops and discuss common GRNs involved in the vascular cambium-driven secondary growth in storage roots using the wealth of information available in Arabidopsis. Finally, we propose future engineering schemes for improving root crop yields by modifying potential key nodes in GRNs.

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Polysaccharides of nutritional interest in jicama (Pachyrhizus erosus) during root development

González-Vázquez

Calderón‐Domínguez

Mora‐Escobedo

et al. 2022

Food Science & Nutrition

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Jicama root applications have focused on their nutraceutical properties without clearly specifying which compounds are related to this effect. Thus, the aim of the present study was to identify the changes in polysaccharides of nutraceutical interest in two commercial jicama roots (YS – Yellow Seed; PS – Purple Seed) during four stages of maturation, focusing on starch, fructooligosaccharides, and pectin (via galacturonic acid), and on their glycemic index, with the goal of determining, if possible, the best cost‐effectiveness between jicama growing stages and nutraceutical effect. Both materials (YS, PS) presented similar growth rates (0.069 and 0.072 cm/day) and final sizes (12.7 ± 1.25, 12.3 ± 1.63 cm). Changes in size were accompanied by changes in protein, fiber, ashes, lipids, and carbohydrates, after 106 or 127 days of growing. It was also found that fructose content was higher than glucose during the maturing stages, possibly because of the hydrolysis of fructooligosaccharides or sucrose for starch production. Concerning inulin, its levels decreased (<6.0%), after the first days (YS: 13.4% ± 0.7%; PS: 8.4% ± 0.2%, 106 days); however, during development, the presence of other fructooligosaccharides was observed (nystose‐YS 106 days 15.8% ± 0.9% and PS‐106 days 18.5% ± 0.1%), while galacturonic acid and native starch levels increased, which must be related to the jicama's low glycemic index found (<25%), and their nutraceutical properties. This work proves the presence of inulin in jicama roots by analytical methods, its dependence on root development and classifies jicama as a low glycemic index food, supporting its nutraceutical character.

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

Abstract: Efficient starch storage in young xylem parenchyma cells is supported by symplasmic phloem unloading and post-phloem transport via parenchymatic vascular rays in the tuberous roots of cassava.

Cited by 43 publications

References 80 publications

The Cassava Source–Sink project: opportunities and challenges for crop improvement by metabolic engineering

The Cassava Source–Sink project: opportunities and challenges for crop improvement by metabolic engineering

Gene Regulatory Network Guided Investigations and Engineering of Storage Root Development in Root Crops

Polysaccharides of nutritional interest in jicama (Pachyrhizus erosus) during root development

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