scholarly journals Phloem loading via the abaxial bundle sheath cells in maize leaves

2020 ◽  
Author(s):  
Margaret Bezrutczyk ◽  
Nora R. Zöllner ◽  
Colin P. S. Kruse ◽  
Thomas Hartwig ◽  
Tobias Lautwein ◽  
...  
Keyword(s):  
Phloem Loading ◽  
Bundle Sheath ◽  
Dorsoventral Patterning ◽  
Phloem Parenchyma ◽  
Bundle Sheath Cells ◽  
Maize Leaves ◽  
Main Pathway ◽  
Rank 2 ◽  
Amino Acid Efflux ◽  
Unique Mechanism

ABSTRACTLeaves are asymmetric, with differential functionalization of abaxial and adaxial tissues. The bundle sheath (BS) surrounding the vasculature of the C3 crop barley is dorsoventrally differentiated into three domains: adaxial structural, lateral S-type, and abaxial L-type. S-type cells seem to transfer assimilates towards the phloem. Here we used single-cell RNA sequencing to investigate BS differentiation in C4 maize. Abaxial BS (abBS) 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 were also identified in the phloem parenchyma (PP). Thus maize acquired a unique mechanism for phloem loading in which abBS cells provide the main pathway for apoplasmic sucrose transfer towards the phloem. This pathway predominates in veins responsible for phloem loading (rank-2 intermediate), while rank-1 intermediate and major veins export sucrose from the phloem parenchyma (PP) adjacent to the sieve element companion cell (SE/CC) complex, as in Arabidopsis. We surmise that abBS identity is subject to dorsoventral patterning and has components of PP identity. These observations provide first insights into the unique transport-specific properties of abBS cells and support for a modification to the canonical phloem loading pathway of maize, which may be generalizable to other C4 monocots.

Respiration in the light measured by 12CO 2 emission in 13CO 2 atmosphere in maize leaves

2001 ◽  
Vol 28 (11) ◽  
pp. 1103 ◽  
Author(s):  
Francesco Loreto ◽  
Violeta Velikova ◽  
Giorgio Di Marco
Keyword(s):  
Gas Exchange ◽  
Mitochondrial Respiration ◽  
Bundle Sheath ◽  
Gas Exchange Parameters ◽  
Low Light ◽  
Light Intensities ◽  
Wide Range ◽  
Bundle Sheath Cells ◽  
Maize Leaves ◽  
Exchange Parameters

The mitochondrial respiration during photosynthesis is difficult to measure and is indirectly estimated mainly in C 3 plants. Loreto et al. [(1999) Australian Journal of Plant Physiology 26, 733–736] have shown that the emission of 12 CO 2 from illuminated leaves exposed to air containing 13 CO 2 measures photorespiration and mitochondrial respiration in C 3 leaves. This method was used to measure the mitochondrial respiration in illuminated maize leaves. The 12 CO 2 emission was steady after 30 s, a time sufficient to label the CO 2 leakage from bundle sheath cells with 13 CO 2 , but not the mitochondrial respiration in the light. The emission was low (0.1–0.4 ppm or 0.2–0.4 µmol m –2 s –1 ) in a wide range of leaf temperatures and light intensities, but increased at light intensities below 200 µmol m –2 s –1 and at temperatures above 42°C. At 120 s after labelling, the leaf was darkened and the emission rapidly matched the mitochondrial respiration measured by gas exchange. The emission of 12 CO 2 in the light was inversely correlated with photosynthesis. This suggested that most of the respiratory CO 2 was refixed by photosynthesis. The amount of refixed intercellular 12 CO 2 was calculated from gas-exchange parameters. It was 60 to 90% of the tota l12 CO 2 in leaves illuminated and exposed to temperatures below 42°C. In leaves with reduced photosynthesis because of exposure to higher temperatures or low light, the 12 CO 2 refixation decreased. The sum of refixed and emitted 12 CO 2 was close to the mitochondrial respiration in the dark. This suggested that in these leaves the mitochondrial respiration was not inhibited in the light. In salt- and water-stressed leaves, however, the sum of refixed and emitted 12 CO 2 was lower than mitochondrial respiration in the dark, suggesting that the mitochondrial respiration may be inhibited in the light.

scholarly journals Complementary DNA Cloning and Characterization of Ferredoxin Localized in Bundle-Sheath Cells of Maize Leaves

1999 ◽  
Vol 119 (2) ◽  
pp. 481-488 ◽  
Author(s):  
Tomohiro Matsumura ◽  
Yoko Kimata-Ariga ◽  
Hitoshi Sakakibara ◽  
Tatsuo Sugiyama ◽  
Hiroshi Murata ◽  
...  
Keyword(s):  
Bundle Sheath ◽  
Dna Cloning ◽  
Complementary Dna ◽  
Bundle Sheath Cells ◽  
Maize Leaves ◽  
Complementary Dna Cloning ◽  
Sheath Cells

bundle sheath defective, a mutation that disrupts cellular differentiation in maize leaves

Development ◽  
1994 ◽  
Vol 120 (3) ◽  
pp. 673-681 ◽  
Author(s):  
J. A. Langdale ◽  
C. A. Kidner
Keyword(s):  
Gene Action ◽  
Morphological Differentiation ◽  
Cell Types ◽  
Bundle Sheath ◽  
Sheath Cell ◽  
Mesophyll Cells ◽  
Bundle Sheath Cell ◽  
Bundle Sheath Cells ◽  
Maize Leaves ◽  
Sheath Cells

Post-primordial differentiation events in developing maize leaves produce two photosynthetic cell types (bundle sheath and mesophyll) that are morphologically and biochemically distinct. We have isolated a mutation that disrupts the differentiation of one of these cell types in light-grown leaves. bundle sheath defective 1-mutable 1 (bsd1-m1) is an unstable allele that was induced by transposon mutagenesis. In the bundle sheath cells of bsd1-m1 leaves, chloroplasts differentiate aberrantly and C4 photosynthetic enzymes are absent. The development of mesophyll cells is unaffected. In dark-grown bsd1-m1 seedlings, morphological differentiation of etioplasts is only disrupted in bundle sheath cells but photosynthetic enzyme accumulation patterns are altered in both cell types. These data suggest that, during normal development, the Bsd1 gene directs the morphological differentiation of chloroplasts in a light-independent and bundle sheath cell-specific fashion. In contrast, Bsd1 gene action on photosynthetic gene expression patterns is cell-type independent in the dark (C3 state) but bundle sheath cell-specific in the light (C4 state). Current models hypothesize that C4 photosynthetic differentiation is achieved through a light-induced interaction between bundle sheath and mesophyll cells (J. A. Langdale and T. Nelson (1991) Trends in Genetics 7, 191–196). Based on the data shown in this paper, we propose that induction of the C4 state restricts Bsd1 gene action to bundle sheath cells.

scholarly journals Bundle sheath cells of small veins in maize leaves are the location of uptake from the xylem

2001 ◽  
Vol 52 (357) ◽  
pp. 709-714 ◽  
Author(s):  
M. Keunecke ◽  
B. Lindner ◽  
U. Seydel ◽  
A. Schulz ◽  
U.P. Hansen
Keyword(s):  
Bundle Sheath ◽  
Bundle Sheath Cells ◽  
Maize Leaves ◽  
Sheath Cells

Control of cellular differentiation in maize leaves

1995 ◽  
Vol 350 (1331) ◽  
pp. 53-57 ◽  
Keyword(s):  
Cellular Differentiation ◽  
Functional Characterization ◽  
Cell Types ◽  
Bundle Sheath ◽  
Gene Products ◽  
Mesophyll Cells ◽  
Bundle Sheath Cells ◽  
Maize Leaves ◽  
Single Cell Type

Mature maize leaves exhibit a series of parallel veins that are surrounded by concentric rings of bundle sheath and mesophyll cells. To identify genes that control cellular differentiation patterns in the leaf, we have isolated a group of mutations that specifically disrupt the differentiation of a single cell-type. In bundle sheath defective ( bsd ) mutant plants, bundle sheath cells fail to differentiate yet mesophyll and all other leaf cell-types develop normally. Morphological and functional characterization of specific bsd mutants ( bsd1, bsd2, bsd3, pg14 and g2 ) reveals that they differ in the degree to which bundle sheath cell differentiation is perturbed. Mutant analysis predicts roles for BSD gene products in normal development.

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