Abscisic Acid- and Stress-Induced Highly Proline-Rich Glycoproteins Regulate Root Growth in Rice

Abstract

In the root of rice (Oryza sativa), abscisic acid (ABA) treatment, salinity, or water deficit stress induces the expression of a family of four genes, REPETITIVE PROLINE-RICH PROTEIN (RePRP). These genes encode two subclasses of novel proline-rich glycoproteins with highly repetitive PX 1 PX 2 motifs, RePRP1 and RePRP2. RePRP orthologs exist only in monocotyledonous plants, and their functions are virtually unknown. Rice RePRPs are heavily glycosylated with arabinose and glucose on multiple hydroxyproline residues. They are significantly different from arabinogalactan proteins that have glycan chains composed of arabinose and galactose. Transient and stable expressions of RePRP-green fluorescent protein reveal that a fraction of this protein is localized to the plasma membrane. In rice roots, ABA treatment increases RePRP expression preferentially in the elongation zone. Overexpression of RePRP in transgenic rice reduces root cell elongation in the absence of ABA, similar to the effect of ABA on wild-type roots. Conversely, simultaneous knockdown of the expression of RePRP1 and RePRP2 reduces the root sensitivity to ABA, indicating that RePRP proteins play an essential role in ABA/stress regulation of root growth and development. Moreover, rice RePRPs specifically interact with a polysaccharide, arabinogalactan, in a dosage-dependent manner. It is suggested that RePRP1 and RePRP2 are functionally redundant suppressors of root cell expansion and probably act through interactions with cell wall components near the plasma membrane.

Transcriptomic reprogramming in soybean seedlings under salt stress

“…Moreover, Glyma.10G080000 (in R‐M18) encodes a hydroxyproline‐rich glycoprotein family protein that is a major structural protein in the cell wall (Table S2). This gene has been shown to be induced by ABA and salt stress in rice (Tseng, Hong, Yu, & Ho, ).…”

The Arabidopsis NAC Transcription Factor ANAC096 Cooperates with bZIP-Type Transcription Factors in Dehydration and Osmotic Stress Responses

“…They are involved in cell organization, oxidative stress, photosynthesis, and defense responses. However, some of them are known to be regulated by ABA (Ton et al, 2009;Kar, 2011;Sreenivasulu et al, 2012;Tseng et al, 2013). It is possible that many of these genes in this group may be transcriptionally activated by ABA at a later time point or higher ABA concentration than we used.…”

Pipeline to Identify Hydroxyproline-Rich Glycoproteins

“…This class was checked for Pro-rich motifs from mammals and other organisms, and no motifs were found to be well represented. Some plant sequences similar to rice OsRePRP1 (Tseng et al, 2013) and AtPRP10 (Rashid and Deyholos, 2011) were found, with a total of 7.3% of class 24 proteins containing either an OsRePRP1 (0.5%) or an AtPRP10/AtPELPK1 (6.8%) Pro-rich motif (Table II).…”

“…4E). AtPELPK1 is localized to the cell wall (Rashid, 2014) and is an IDP, yet it remains uncertain if it and OsRePRP1 (Tseng et al, 2013) are bona fide Hyp-containing glycoproteins. Determining if and where Pro-to-Hyp modification (and subsequent glycosylation) occurs in the novel motifs identified within class 24 will require experimental approaches such as in planta expression.…”