Question

Discuss signaling molecules that regulate vascular development in the root

Answer 1

In plants there are various types of signaling molecules present which regulate the vascular development. Small peptides are emerging as key signaling molecules that coordinate various aspects of developmental processes in plants.

1.Signaling Peptides in Primary Root Development

The Roles of RGF Peptides and Their Receptors in Root Meristem Maintenance and the Gravitropic Response

Tyrosine sulfation is a post-translational modification of peptide hormones that is mediated by tyrosylprotein sulfotransferase (TPST). The arabidopsis genome has only one TPST gene, and the loss-of-function mutant tpst-1 shows pleiotropic phenotypes including severely shortened roots with a reduction in root meristem size . Application of synthetic and sulfated ROOT MERISTEM GROWTH FACTOR 1 (RGF1) peptides restores root meristem activity in the tpst-1 mutant, indicating that this peptide is required for root stem cell maintenance and that sulfation of the tyrosine residue of RGF1 is crucial for its activity.

2.Signaling Peptides in Lateral Root (LR) Development

The Roles of CLE and CEP Peptides and Their Receptors in N-Responsive LR Growth

Some CLE peptides function in LR growth in response to changing levels of N in soil. CLE1, CLE3, CLE4, and CLE7 are expressed predominantly in the pericycle, and their expression in arabidopsis roots is downregulated by N supply, and is upregulated by low levels of N . Overexpression of these CLE genes inhibits LR growth , indicating that these CLE peptides act as negative regulators of LR growth. Because the clv1-1 mutant has longer LRs under low-N conditions, CLV1 may be a receptor for CLE peptides . Root-specific expression of CLE3 inhibits LR formation in the wild type but not in the clv1 mutant, indicating that CLE-dependent inhibition of LR formation requires CLV1.These results show that a CLE–CLV1 signaling module is important in the regulation of LR growth in response to changing levels of N in the soil .

3.

Signaling Peptides in Root Hair Formation

The Roles of RALF Peptide and Its Receptor in Root Hair Development

RALF peptides regulate root hair development. Arabidopsis plants overexpressing RALF1 show inhibited root hair growth , and application of synthetic RALF peptides produces a similar effect. RALF peptides stimulate the phosphorylation of H+-ATPase 2 (AHA2) to inhibit its proton pump activity, and the consequent increase in apoplastic pH reduces cell elongation , indicating that RALF peptides control root hair formation via the regulation of cell elongation. FERONIA (FER) is a receptor for RALF peptides. The fer knockout mutants exhibit root hair defects and are insensitive to RALF treatment. Activation of FER by RALF results in the phosphorylation of AHA2, which increases extracellular alkalinization, reducing cell elongation . FER also interacts with several plant-specific guanine nucleotide exchange factors (RopGEFs), such as RopGEF4 and RopGEF10, to activate the plant RHO GTPases (RAC/ROP) signaling pathway . Regulated RAC/ROP activity controls the production of NADPH-dependent reactive oxygen species (ROS) , and spatially regulated accumulation of ROS leads to enhancement of polarized root hair growth. The RALF–FER pair requires additional components, such as LORELEI-LIKE-GPI-ANCHORED PROTEIN 1 (LLG1) and RPM1-induced protein kinase (RIPK), to trigger activation of the GEF–ROP pathway that mediates auxin-dependent root hair development .

4.Signaling Peptides in Root Nodulation

The Roles of CLE Homologs and Their Receptors in Regulating Root Nodulation

Homologs of CLE peptides and CLV receptors [CLV1, Receptor-like protein kinase 2 (RPK2), and CLV2–CRN] regulate nodule numbers in legumes.

There are also various types of peptides who also signaling for the development of the vascular tissue.

If there was any problem to find out any full name of peptides then comment on it.

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