Proline-rich protein-like PRPL1 controls elongation of root hairs in Arabidopsis thaliana

Abstract

The synthesis and composition of cell walls is dynamically adapted in response to many developmental and environmental signals. In this respect, cell wall proteins involved in controlling cell elongation are critical for cell development. Transcriptome analysis identified a gene in Arabidopsis thaliana, which was named proline-rich protein-like, AtPRPL1, based on sequence similarities from a phylogenetic analysis. The most resemblance was found to AtPRP1 and AtPRP3 from Arabidopsis, which are known to be involved in root hair growth and development. In A. thaliana four proline-rich cell wall protein genes, playing a role in building up the cross-connections between cell wall components, can be distinguished. AtPRPL1 is a small gene that in promoter::GUS (β-glucuronidase) analysis has high expression in trichoblast cells and in the collet. Chemical or mutational interference with root hair formation inhibited this expression. Altered expression levels in knock-out or overexpression lines interfered with normal root hair growth and etiolated hypocotyl development, but Fourier transform-infrared (FT-IR) analysis did not identify consistent changes in cell wall composition of root hairs and hypocotyl. Co-localization analysis of the AtPRPL1-green fluorescent protein (GFP) fusion protein and different red fluorescent protein (RFP)-labelled markers confirmed the presence of AtPRPL1-GFP in small vesicles moving over the endoplasmic reticulum. Together, these data indicate that the AtPRPL1 protein is involved in the cell's elongation process. How exactly this is achieved remains unclear at present.

A Spatiotemporal DNA Endoploidy Map of the Arabidopsis Root Reveals Roles for the Endocycle in Root Development and Stress Adaptation

“…A putative scenario might be that the high ploidy level is required for an increased metabolic output required for tip outgrowth. Root hairs have been found to express unique cell expansion and cell wall-modifying enzymes, including specific expansins and pectin-interacting proline-rich proteins (Bernhardt and Tierney, 2000;Boron et al, 2014;Cho and Cosgrove, 2002;Vissenberg et al, 2001).…”

Integration of transcriptomic and proteomic analysis towards understanding the systems biology of root hairs

“…Interestingly, the gene At5G05500 was co-expressed with many root hair-related genes, indicating a possible role of this gene in root hair development. Indeed, a recent study showed that At5G05500 shared high similarities with AtPRP1 and At-PRP3, and analysis of knock-out or overexpression lines indicated that At5G05500 was involved in root hair elongation process [65]. In addition, this sub-cluster contained several function unannotated genes that are worthy of further research.…”

Multifunctional proline rich proteins and their role in regulating cellular proline content in plants under stress

“…Under normal conditions, PRPs are constitutively expressed in roots and vegetative tissues (Bouton et al 2005, Peng et al 2015. The PRPL1 gene of Arabidopsis is peculiarly expressed in root hairs and triggers their elongation (Boron et al 2014). Involvement of PRPs in cell elongation is further supported by overexpression of the HyPRP gene in tobacco BY-2 cell lines where calli size increases in suspension culture as well as on solid media (Dvorakova et al 2012).…”