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Evidence for phloem loading via the abaxial bundle sheath cells in maize leaves

Leaves are asymmetric, with different functions for adaxial and abaxial tissue. The bundle sheath (BS) of C(3) barley (Hordeum vulgare) is dorsoventrally differentiated into three types of cells: adaxial structural, lateral S-type, and abaxial L-type BS cells. Based on plasmodesmatal connections bet...

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Autores principales: Bezrutczyk, Margaret, Zöllner, Nora R, Kruse, Colin P S, Hartwig, Thomas, Lautwein, Tobias, Köhrer, Karl, Frommer, Wolf B, Kim, Ji-Yun
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Oxford University Press 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8136869/
https://www.ncbi.nlm.nih.gov/pubmed/33955497
http://dx.doi.org/10.1093/plcell/koaa055
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author Bezrutczyk, Margaret
Zöllner, Nora R
Kruse, Colin P S
Hartwig, Thomas
Lautwein, Tobias
Köhrer, Karl
Frommer, Wolf B
Kim, Ji-Yun
author_facet Bezrutczyk, Margaret
Zöllner, Nora R
Kruse, Colin P S
Hartwig, Thomas
Lautwein, Tobias
Köhrer, Karl
Frommer, Wolf B
Kim, Ji-Yun
author_sort Bezrutczyk, Margaret
collection PubMed
description Leaves are asymmetric, with different functions for adaxial and abaxial tissue. The bundle sheath (BS) of C(3) barley (Hordeum vulgare) is dorsoventrally differentiated into three types of cells: adaxial structural, lateral S-type, and abaxial L-type BS cells. Based on plasmodesmatal connections between S-type cells and mestome sheath (parenchymatous cell layer below bundle sheath), S-type cells likely transfer assimilates toward the phloem. Here, we used single-cell RNA sequencing to investigate BS differentiation in C(4) maize (Zea mays L.) plants. Abaxial BS ((ab)BS) cells of rank-2 intermediate veins specifically expressed three SWEET sucrose uniporters (SWEET13a, b, and c) and UmamiT amino acid efflux transporters. SWEET13a, b, c mRNAs were also detected in the phloem parenchyma (PP). We show that maize has acquired a mechanism for phloem loading in which (ab)BS cells provide the main route for apoplasmic sucrose transfer toward the phloem. This putative route predominates in veins responsible for phloem loading (rank-2 intermediate), whereas rank-1 intermediate and major veins export sucrose from the PP adjacent to the sieve element companion cell complex, as in Arabidopsis thaliana. We surmise that (ab)BS identity is subject to dorsoventral patterning and has components of PP identity. These observations provide insights into the unique transport-specific properties of (ab)BS cells and support a modification to the canonical phloem loading pathway in maize.
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spelling pubmed-81368692021-05-25 Evidence for phloem loading via the abaxial bundle sheath cells in maize leaves Bezrutczyk, Margaret Zöllner, Nora R Kruse, Colin P S Hartwig, Thomas Lautwein, Tobias Köhrer, Karl Frommer, Wolf B Kim, Ji-Yun Plant Cell Research Articles Leaves are asymmetric, with different functions for adaxial and abaxial tissue. The bundle sheath (BS) of C(3) barley (Hordeum vulgare) is dorsoventrally differentiated into three types of cells: adaxial structural, lateral S-type, and abaxial L-type BS cells. Based on plasmodesmatal connections between S-type cells and mestome sheath (parenchymatous cell layer below bundle sheath), S-type cells likely transfer assimilates toward the phloem. Here, we used single-cell RNA sequencing to investigate BS differentiation in C(4) maize (Zea mays L.) plants. Abaxial BS ((ab)BS) cells of rank-2 intermediate veins specifically expressed three SWEET sucrose uniporters (SWEET13a, b, and c) and UmamiT amino acid efflux transporters. SWEET13a, b, c mRNAs were also detected in the phloem parenchyma (PP). We show that maize has acquired a mechanism for phloem loading in which (ab)BS cells provide the main route for apoplasmic sucrose transfer toward the phloem. This putative route predominates in veins responsible for phloem loading (rank-2 intermediate), whereas rank-1 intermediate and major veins export sucrose from the PP adjacent to the sieve element companion cell complex, as in Arabidopsis thaliana. We surmise that (ab)BS identity is subject to dorsoventral patterning and has components of PP identity. These observations provide insights into the unique transport-specific properties of (ab)BS cells and support a modification to the canonical phloem loading pathway in maize. Oxford University Press 2021-01-07 /pmc/articles/PMC8136869/ /pubmed/33955497 http://dx.doi.org/10.1093/plcell/koaa055 Text en © The Author(s) 2021. Published by Oxford University Press on behalf of American Society of Plant Biologists. https://creativecommons.org/licenses/by/4.0/This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/ (https://creativecommons.org/licenses/by/4.0/) ), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
spellingShingle Research Articles
Bezrutczyk, Margaret
Zöllner, Nora R
Kruse, Colin P S
Hartwig, Thomas
Lautwein, Tobias
Köhrer, Karl
Frommer, Wolf B
Kim, Ji-Yun
Evidence for phloem loading via the abaxial bundle sheath cells in maize leaves
title Evidence for phloem loading via the abaxial bundle sheath cells in maize leaves
title_full Evidence for phloem loading via the abaxial bundle sheath cells in maize leaves
title_fullStr Evidence for phloem loading via the abaxial bundle sheath cells in maize leaves
title_full_unstemmed Evidence for phloem loading via the abaxial bundle sheath cells in maize leaves
title_short Evidence for phloem loading via the abaxial bundle sheath cells in maize leaves
title_sort evidence for phloem loading via the abaxial bundle sheath cells in maize leaves
topic Research Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8136869/
https://www.ncbi.nlm.nih.gov/pubmed/33955497
http://dx.doi.org/10.1093/plcell/koaa055
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