Oligogalacturonides inhibit growth and induce changes in S6K phosphorylation in maize (Zea mays L. var. Chalqueño)

Abstract

Cell growth is regulated by the target of rapamycin (TOR) signaling pathway, which integrates environmental cues in eukaryotes. In plants the final organ size is determined by the number and cell size. Several proteins involved in the TOR signaling pathway are conserved in plants, although a differential regulation has been proposed because insensitivity to rapamycin by Arabidopsis thaliana was reported. Reports about the role of auxin in the activation of maize S6 ribosomal protein kinase (S6K), a downstream substrate of TOR, have been published indicating a central role of the TOR pathway in the regulation of plant growth. However, in addition to phytohormones, there are a variety of plant growth regulators, including cell wall fragments called oligogalacturonides (OGs). Here we report the effect of OGs on maize growth and development, as well as on S6K activation. We found that oligogalacturonides inhibit coleoptile growth and modify root architecture of maize seedlings. Western blot analyses indicated a modulation of maize S6K activity from seedlings and embryonic axes in response to OGs treatment. These results show that oligosaccharides regulate growth and development through the modulation of TOR signaling pathway in maize.

Etiolated Seedling Development Requires Repression of Photomorphogenesis by a Small Cell-Wall-Derived Dark Signal

“…digest did not have a significant effect on the photomorphogenic mutants cop1-4 and pifq, but it decreased the extent of cotyledon opening in det1 (Figures S5A and S5B). OGs were reported to inhibit growth [13,48], and this was also observed in both light-and dark-grown seedlings through an inhibition of root growth ( Figures S5A-S5D). Given that skotomorphogenesis was restored in dez by a digest of PGA, which constitutes the simple, chemically unmodified backbone of homogalacturonan, we next tested the galacturonic monomer and oligomers of increasing lengths (Table S2).…”

Homogalacturonan-modifying enzymes: structure, expression, and roles in plants

“…These regulation pathways, in particular that of auxin, may be controlled through OG-mediated negative feedback (Ferrari et al, 2013). The antagonism between auxin and OGs has previously been shown during root formation in tobacco (Bellincampi et al, 1993) and by using exogenous OGs in maize seedlings (Peña-Uribe et al, 2012). Exogenous OGs inhibit the expression of auxin-induced genes (IAA5, SAUR16, etc.…”

The Role of Ribosomal Protein S6 Kinases in Plant Homeostasis

“…Growth inhibition also induces changes in S6K activity. For example, treatment of 10-day-old maize seedlings with high doses of oligogalacturonides (OGs), a plant growth regulator which inhibits coleoptile growth, induced changes in ZmS6K activity in a similar way to rapamycin-treated seedling ( Peña-Uribe et al, 2012 ). Varying degrees of rpS6 phosphorylation was also observed in Arabidopsis leaves at different levels of photosynthetic capacity, suggesting that S6Ks could be modulated by photosynthesis via TOR ( Boex-Fontvieille et al, 2013 ).…”