scholarly journals Bundle sheath suberisation is required for C4 photosynthesis in a Setaria viridis mutant

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Florence R. Danila ◽  
Vivek Thakur ◽  
Jolly Chatterjee ◽  
Soumi Bala ◽  
Robert A. Coe ◽  
...  
Keyword(s):  
Cell Wall ◽  
C4 Photosynthesis ◽  
Nile Red ◽  
Bundle Sheath ◽  
Setaria Viridis ◽  
Coding Region ◽  
Gene Coding ◽  
Suberin Lamellae ◽  
Type C ◽  
Gas Tight

AbstractC4 photosynthesis provides an effective solution for overcoming the catalytic inefficiency of Rubisco. The pathway is characterised by a biochemical CO2 concentrating mechanism that operates across mesophyll and bundle sheath (BS) cells and relies on a gas tight BS compartment. A screen of a mutant population of Setaria viridis, an NADP-malic enzyme type C4 monocot, generated using N-nitroso-N-methylurea identified a mutant with an amino acid change in the gene coding region of the ABCG transporter, a step in the suberin synthesis pathway. Here, Nile red staining, TEM, and GC/MS confirmed the alteration in suberin deposition in the BS cell wall of the mutant. We show that this has disrupted the suberin lamellae of BS cell wall and increased BS conductance to CO2 diffusion more than two-fold in the mutant. Consequently, BS CO2 partial pressure is reduced and CO2 assimilation was impaired in the mutant. Our findings provide experimental evidence that a functional suberin lamellae is an essential anatomical feature for efficient C4 photosynthesis in NADP-ME plants like S. viridis and have implications for engineering strategies to ensure future food security.

scholarly journals Changes in the plasmodesma structure and permeability at the bundle sheath and mesophyll interface during the maize C4 leaf development

2020 ◽  
Author(s):  
Peng Gao ◽  
Baijuan Du ◽  
Pinghua Li ◽  
Byung-Ho Kang
Keyword(s):  
Cell Wall ◽  
Organic Acids ◽  
Molecular Diffusion ◽  
C4 Photosynthesis ◽  
Solute Concentration ◽  
Bundle Sheath ◽  
Solute Diffusion ◽  
Cell Wall Modification ◽  
Maize Leaf ◽  
Kranz Anatomy

AbstractPlasmodesmata are intercellular channels that facilitate molecular diffusion between neighboring plant cells. The development and functions of plasmodesmata are controlled by multiple intra- and intercellular signaling pathways. Plasmodesmata are critical for dual-cell C4 photosynthesis in maize because plasmodesmata at the mesophyll and bundle sheath interface mediate exchange of CO2-carrying organic acids. We examined developmental profiles of plasmodesmata and chloroplasts in the maize leaf from young cells in the base to mature cell in the tip using microscopy approaches. Young mesophyll and bundle sheath cells in the leaf base had proplastids, and their plasmodesmata were simple, devoid of cytoplasmic sleeves. In maturing cells where Kranz anatomy and dimorphic chloroplasts were evident, we observed extensive remodeling of plasmodesmata that included acquisition of an electron-dense ring on the mesophyll side and cytoplasmic sleeves on the bundle sheath side. Interestingly, the changes in plasmodesmata involved a drop in symplastic dye mobility and suberin accumulation in the cell wall, implying a more stringent mesophyll-bundle sheath transport. We compared kinetics of the plasmodesmata and the cell wall modification in wildtype leaves with leaves from ppdk and dct2 mutants with defective C4 pathways. Plasmodesmata development, symplastic transport inhibition, and cell wall suberization were accelerated in the mutant lines, probably due to the aberrant C4 cycle. Transcriptomic analyses of the mutants confirmed the expedited changes in the cell wall. Our results suggest that a regulatory machinery at the mesophyll-bundle sheath boundary suppresses erroneous flux of C4 metabolites in the maize leaf.Significance StatementPlasmodesmata in the maize Kranz anatomy mediate the exchange of organic acids between mesophyll and bundle sheath. Since solute diffusion through plasmodesmata is governed by solute concentration gradients, a balanced distribution of C4 metabolites is critical for concentration of CO2 in the bundle sheath. Plasmodesmata bridging the mesophyll and bundle sheath cytoplasm have a cylindrical cavity, which can facilitate molecular movements, and a valve-like attachment. Construction of the sophisticated plasmodesmata was linked to C4 photosynthesis, and plasmodesmata assembly finished more rapidly in maize mutants with defective C4 pathways than in wild-type plants. These results suggest that the specialized plasmodesmata contribute to controlled transport of C4 metabolites.

scholarly journals The maize Aliphatic Suberin Feruloyl Transferase genes affect leaf water movement but are dispensable for bundle sheath CO2 concentration

2020 ◽  
Author(s):  
Rachel A. Mertz ◽  
Patrick Ellsworth ◽  
Patricia Ellsworth ◽  
S. Lori Tausta ◽  
Susanne von Caemmerer ◽  
...  
Keyword(s):  
Cell Wall ◽  
Carbon Fixation ◽  
Water Movement ◽  
Bundle Sheath ◽  
Leaf Water ◽  
Loss Of Function ◽  
Wild Type ◽  
Ambient Conditions ◽  
Mesophyll Cells ◽  
Suberin Lamellae

ABSTRACTC4 grasses often outperform C3 species under hot, arid conditions due to superior water and nitrogen use efficiencies and lower rates of photorespiration. A method of concentrating CO2 around the site of carbon fixation in the bundle sheath (BS) is required to realize these gains. In NADP-malic enzyme (NADP-ME)-type C4 grasses such as maize, suberin deposition in the BS cell wall is hypothesized to act as a diffusion barrier to CO2 escape and O2 entry from surrounding mesophyll cells. Suberin is a heteropolyester comprised of acyl-lipid-derived aliphatic and phenylpropanoid-derived aromatic components. To disrupt BS suberization, we mutated two paralogously duplicated, unlinked maize orthologues of Arabidopsis thaliana ALIPHATIC SUBERIN FERULOYL TRANSFERASE, ZmAsft1 and ZmAsft2, using closely linked Dissociation transposons. Loss-of-function double mutants revealed a 97% reduction in suberin-specific omega-hydroxy fatty acids without a stoichiometric decrease in ferulic acid. However, BS suberin lamellae were deficient in electron opaque material, and cohesion between the suberin lamellae and polysaccharide cell walls was attenuated in double mutants. There were no other morphological phenotypes under ambient conditions. Furthermore, there was no significant effect on net CO2 assimilation at any intercellular CO2 concentration, and no effect on 13C isotope discrimination relative to wild type. Thus, ZmAsft expression is not required to establish a functional CO2 concentrating mechanism in in maize. Double mutant leaves exhibit elevated cell wall elasticity, transpirational, and stomatal conductance relative to WT. Thus, the ZmAsft genes are dispensable for gas exchange barrier function but may be involved in regulation of leaf water movement.One-sentence SummaryDouble mutants of two paralogously duplicated maize Aliphatic Suberin Feruloyl Transferase (ZmAsft) genes exhibit reduced aliphatic suberin content, cell wall cohesion defects, and elevated leaf transpiration, but no changes in CO2 assimilation relative to wild type.

scholarly journals Accelerated remodeling of the mesophyll-bundle sheath interface in the maize C4 cycle mutant leaves

2021 ◽  
Author(s):  
Peng Gao ◽  
Pengfei Wang ◽  
Baijuan Du ◽  
Pinghua Li ◽  
Byung-Ho Kang
Keyword(s):  
Cell Wall ◽  
Organic Acids ◽  
C4 Photosynthesis ◽  
Bundle Sheath ◽  
Wild Type ◽  
Symplastic Transport ◽  
Maize Leaf ◽  
Kranz Anatomy ◽  
Chloroplast Differentiation ◽  
Kinetics Of

Abstract C4 photosynthesis in the maize leaf involves the exchange of organic acids between mesophyll (M) and the bundle sheath (BS) cells. The transport is mediated by plasmodesmata embedded in the suberized cell wall. We examined the maize Kranz anatomy with a focus on the plasmodesma and cell wall suberization with microscopy methods. In the young leaf zone where M and BS cells had indistinguishable proplastids, plasmodesmata were simple and no suberin was detected. In leaf zones where dimorphic chloroplasts were evident, the plasmodesma acquired sphincter and cytoplasmic sleeves, and suberin was discerned. These modifications were accompanied by a drop in symplastic dye mobility at the M-BS boundary. We compared the kinetics of chloroplast differentiation and the modifications in M-BS connectivity in ppdk and dct2 mutants where C4 cycle is affected. The rate of chloroplast diversification did not alter, but plasmodesma remodeling, symplastic transport inhibition, and cell wall suberization were observed from younger leaf zone in the mutants than in wild type. Our results indicate that inactivation of the C4 genes accelerated the changes in the M-BS interface and the reduced permeability suggests that symplastic transport between M and BS could be gated probably for suppressing erroneous flux of C4 metabolites.

scholarly journals Aspergillus nidulans wetA activates spore-specific gene expression.

1991 ◽  
Vol 11 (1) ◽  
pp. 55-62 ◽  
Author(s):  
M A Marshall ◽  
W E Timberlake
Keyword(s):  
Gene Expression ◽  
Cell Wall ◽  
Aspergillus Nidulans ◽  
Gene Activation ◽  
Regulatory Function ◽  
Specific Gene ◽  
Coding Region ◽  
Vegetative Cells ◽  
Mutant Strains ◽  
Late Stages

The Aspergillus nidulans wetA gene is required for synthesis of cell wall layers that make asexual spores (conidia) impermeable. In wetA mutant strains, conidia take up water and autolyze rather than undergoing the final stages of maturation. wetA is activated during conidiogenesis by sequential expression of the brlA and abaA regulatory genes. To determine whether wetA regulates expression of other sporulation-specific genes, its coding region was fused to a nutritionally regulated promoter that permits gene activation in vegetative cells (hyphae) under conditions that suppress conidiation. Expression of wetA in hyphae inhibited growth and caused excessive branching. It did not lead to activation of brlA or abaA but did cause accumulation of transcripts from genes that are normally expressed specifically during the late stages of conidiation and whose mRNAs are stored in mature spores. Thus, wetA directly or indirectly regulates expression of some spore-specific genes. At least one gene (wA), whose mRNA does not occur in spores but rather accumulates in the sporogenous phialide cells, was activated by wetA, suggesting that wetA may have a regulatory function in these cells as well as in spores. We propose that wetA is responsible for activating a set of genes whose products make up the final two conidial wall layers or direct their assembly and through this activity is responsible for acquisition of spore dormancy.

Nitrate metabolism in relation to the aspartate-type C-4 pathway of photosynthesis in Eleusine coracana

1974 ◽  
Vol 52 (12) ◽  
pp. 2599-2605 ◽  
Author(s):  
C. K. M. Rathnam ◽  
V. S. R. Das
Keyword(s):  
Glutamate Dehydrogenase ◽  
Eleusine Coracana ◽  
Bundle Sheath ◽  
Chloroplast Envelope ◽  
Mesophyll Cells ◽  
Bundle Sheath Cells ◽  
Nitrate Metabolism ◽  
Type C ◽  
Envelope Membranes ◽  
Sheath Cells

The intercellular and intracellular distributions of nitrate assimilating enzymes were studied. Nitrate reductase was found to be localized on the chloroplast envelope membranes. The chloroplastic NADPH – glutamate dehydrogenase was concentrated in the mesophyll cells. The extrachloroplastic NADH – glutamate dehydrogenase was localized in the bundle sheath cells. Glutamate synthesized in the mesophyll chloroplasts was interpreted to be utilized exclusively in the synthesis of aspartate, while in the bundle sheath cells it was thought to be consumed in other cellular metabolic processes. Based on the results, a scheme is proposed to account for the nitrate metabolism in the leaves of Eleusine coracana Gaertn. in relation to its aspartate-type C-4 pathway of photosynthesis.

scholarly journals Setaria viridis: A Model for C4 Photosynthesis

2010 ◽  
Vol 22 (8) ◽  
pp. 2537-2544 ◽  
Author(s):  
Thomas P. Brutnell ◽  
Lin Wang ◽  
Kerry Swartwood ◽  
Alexander Goldschmidt ◽  
David Jackson ◽  
...  
Keyword(s):  
C4 Photosynthesis ◽  
Setaria Viridis

scholarly journals Hypolignification: A Decisive Factor in the Development of Hyperhydricity

Plants ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 2625
Author(s):  
Nurashikin Kemat ◽  
Richard G. F. Visser ◽  
Frans A. Krens
Keyword(s):  
Cell Wall ◽  
Lignin Content ◽  
Coumaric Acid ◽  
Wild Type ◽  
Higher Plant ◽  
Gene Coding ◽  
Phenylpropanoid Biosynthesis ◽  
Total Lignin ◽  
Total Lignin Content

One of the characteristics of hyperhydric plants is the reduction of cell wall lignification (hypolignification), but how this is related to the observed abnormalities of hyperhydricity (HH), is still unclear. Lignin is hydrophobic, and we speculate that a reduction in lignin levels leads to more capillary action of the cell wall and consequently to more water in the apoplast. p-coumaric acid is the hydroxyl derivative of cinnamic acid and a precursor for lignin and flavonoids in higher plant. In the present study, we examined the role of lignin in the development of HH in Arabidopsis thaliana by checking the wild-types (Ler and Col-0) and mutants affected in phenylpropanoid biosynthesis, in the gene coding for cinnamate 4-hydroxylase, C4H (ref3-1 and ref3-3). Exogenously applied p-coumaric acid decreased the symptoms of HH in both wild-type and less-lignin mutants. Moreover, the results revealed that exogenously applied p-coumaric acid inhibited root growth and increased the total lignin content in both wild-type and less-lignin mutants. These effects appeared to diminish the symptoms of HH and suggest an important role for lignin in HH.

scholarly journals In silico analyses of CD14 molecule reveals significant evolutionary diversity potentially associated with speciation and variable immune response in mammals

2019 ◽  
Author(s):  
Olanrewaju B Morenikeji ◽  
Bolaji N Thomas
Keyword(s):  
Immune Response ◽  
Complex Disease ◽  
Mammalian Species ◽  
Coding Region ◽  
Protein Protein Interaction ◽  
Species Response ◽  
Gene Coding ◽  
Protein Interactome ◽  
Mutational Hotspots ◽  
Leucine Rich Repeats

Cluster differentiation gene (CD14) is a family of monocyte differentiating genes that works in conjunction with lipopolysaccharide binding protein (LBP), forming a complex with TLR4 or LY96 to mediate innate immune response to pathogens. In this paper, we used different computational methods to elucidate the evolution of CD14 gene coding region in 14 mammalian species. Our analyses identified leucine rich repeats (LRRs) as the only significant domain across the CD14 protein of the 14 species, presenting with frequencies ranging from 1-4. Importantly, we found signal peptides located at mutational hotspots demonstrating this gene is conserved across these species. Out of the 10 selected variants analyzed in this study, only 6 were predicted to possess significant deleterious effect. Our predicted protein interactome showed a significant varying protein-protein interaction with CD14 protein across the species. This may be important for drug target and therapeutic manipulation for the treatment of many diseases. We conclude that these results contribute to our understanding of the CD14 molecular evolution, which underlays varying species response to complex disease traits.

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