Monocotyledonous plants graft at the embryonic root–shoot interface

Mutation of the SCARECROW (SCR) gene results in a radial pattern defect, loss of a ground tissue layer, in the root. Analysis of the shoot phenotype of scr mutants revealed that both hypocotyl and shoot inflorescence also have a radial pattern defect, loss of a normal starch sheath layer, and consequently are unable to sense gravity in the shoot. Analogous to its expression in the endodermis of the root, SCR is expressed in the starch sheath of the hypocotyl and inflorescence stem. The SCR expression pattern in leaf bundle sheath cells and root quiescent center cells led to the identification of additional phenotypic defects in these tissues. SCR expression in a pin-formed mutant background suggested the possible origins of the starch sheath in the shoot inflorescence. Analysis of SCR expression and the mutant phenotype from the earliest stages of embryogenesis revealed a tight correlation between defective cell divisions and SCR expression in cells that contribute to ground tissue radial patterning in both embryonic root and shoot. Our data provides evidence that the same molecular mechanism regulates the radial patterning of ground tissue in both root and shoot during embryogenesis as well as postembryonically.

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Mutations in the HYDRA1 gene of Arabidopsis perturb cell shape and disrupt embryonic and seedling morphogenesis

Development ◽

10.1242/dev.124.21.4415 ◽

1997 ◽

Vol 124 (21) ◽

pp. 4415-4424 ◽

Cited By ~ 2

Author(s):

J.F. Topping ◽

V.J. May ◽

P.R. Muskett ◽

K. Lindsey

Keyword(s):

Cell Expansion ◽

Cell Shape ◽

Bilateral Symmetry ◽

Variable Number ◽

Morphological Development ◽

Size And Shape ◽

Radial Patterning ◽

Protein Functions ◽

Expansion System ◽

Embryonic Root

Mutations in the HYDRA1 (HYD1) gene of Arabidopsis thaliana can prevent normal morphological development of embryos and seedlings. Three allelic mutants (hydra 1–1, hydra1-2 and hydra1-3) have been identified, and in each the seedling is characterized by having a variable number of cotyledons, a short and wide hypocotyl and a much reduced root system. hydra1 embryos appear to develop normally to the octant stage, but fail to establish a distinct protoderm and lack bilateral symmetry, developing multiple cotyledonary primordia of irregular size and shape. Cells of the embryo proper, but not the suspensor, exhibit abnormalities in size and shape. The hydra1 embryo fails to develop an embryonic root, but embryos and seedlings express molecular markers of apical-basal polarity. Mutant seedlings produce leaves to form a small cabbage-like habit and may occasionally produce sterile flowers, though the mutation is commonly seedling-lethal. hydra1 seedlings exhibit abnormal radial patterning, but nevertheless express at least one molecular marker of vascular cell differentiation. A model is proposed in which the HYDRA1 protein functions as an essential component of the cell expansion system.

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Two Wheat Cultivars with Contrasting Post-Embryonic Root Biomass Differ in Shoot Re-Growth after Defoliation: Implications for Breeding Grazing Resilient Forages

Plants ◽

10.3390/plants8110470 ◽

2019 ◽

Vol 8 (11) ◽

pp. 470

Author(s):

Paez-Garcia ◽

Liao ◽

Blancaflor

Keyword(s):

Winter Wheat ◽

Root Growth ◽

Root System ◽

Aboveground Biomass ◽

Root Traits ◽

Shoot Biomass ◽

Wheat Cultivars ◽

Leaf Clipping ◽

The Impact ◽

Embryonic Root

The ability of forages to quickly resume aboveground growth after grazing is a trait that enables farmers to better manage their livestock for maximum profitability. Leaf removal impairs root growth. As a consequence of a deficient root system, shoot re-growth is inhibited leading to poor pasture performance. Despite the importance of roots for forage productivity, they have not been considered as breeding targets for improving grazing resilience due in large part to the lack of knowledge on the relationship between roots and aboveground biomass re-growth. Winter wheat (Triticum aestivum) is extensively used as forage source in temperate climates worldwide. Here, we investigated the impact of leaf clipping on specific root traits, and how these influence shoot re-growth in two winter wheat cultivars (i.e., Duster and Cheyenne) with contrasting root and shoot biomass. We found that root growth angle and post-embryonic root growth in both cultivars are strongly influenced by defoliation. We discovered that Duster, which had less post-embryonic roots before defoliation, reestablished its root system faster after leaf cutting compared with Cheyenne, which had a more extensive pre-defoliation post-embryonic root system. Rapid resumption of root growth in Duster after leaf clipping was associated with faster aboveground biomass re-growth even after shoot overcutting. Taken together, our results suggest that lower investments in the production of post-embryonic roots presents an important ideotype to consider when breeding for shoot re-growth vigor in dual purpose wheat.

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