Characterization of a Small Auxin-Up RNA (SAUR)-Like Gene Involved in Arabidopsis thaliana Development

Abstract

The root of Arabidopsis thaliana is used as a model system to unravel the molecular nature of cell elongation and its arrest. From a micro-array performed on roots that were treated with aminocyclopropane-1-carboxylic acid (ACC), the precursor of ethylene, a Small auxin-up RNA (SAUR)-like gene was found to be up regulated. As it appeared as the 76th gene in the family, it was named SAUR76. Root and leaf growth of overexpression lines ectopically expressing SAUR76 indicated the possible involvement of the gene in the division process. Using promoter::GUS and GFP lines strong expression was seen in endodermal and pericycle cells at the end of the elongation zone and during several stages of lateral root primordia development. ACC and IAA/NAA were able to induce a strong up regulation of the gene and changed the expression towards cortical and even epidermal cells at the beginning of the elongation zone. Confirmation of this up regulation of expression was delivered using qPCR, which also indicated that the expression quickly returned to normal levels when the inducing IAA-stimulus was removed, a behaviour also seen in other SAUR genes. Furthermore, confocal analysis of protein-GFP fusions localized the protein in the nucleus, cytoplasm and plasma membrane. SAUR76 expression was quantified in several mutants in ethylene and auxin-related pathways, which led to the conclusion that the expression of SAUR76 is mainly regulated by the increase in auxin that results from the addition of ACC, rather than by ACC itself.

Arabidopsis SAURs are critical for differential light regulation of the development of various organs

“…Previous studies have shown that ectopic expression of several SAUR family genes resulted in elongated hypocotyls in the light and that plants overexpressing SAUR19 exhibited opened cotyledons in the dark (23)(24)(25). However, several other SAURs have been suggested to inhibit cell expansion in certain organs (26)(27)(28). To test the effects of lirSAURs on plant growth, we generated transgenic lines overexpressing SAUR14, SAUR50, and SAUR65, which were selected to represent classes 1, 2, and 3, respectively.…”

“…Based on microarray analysis, about half of SAURs are up-regulated by auxin treatment in Arabidopsis (22). Overexpression of several distinct SAUR genes resulted in increased growth of cotyledons, hypocotyls, or roots, respectively (23)(24)(25), whereas a few SAURs have been suggested to negatively regulate cell growth in specific organs (26)(27)(28). Recently, it has been found that SAURs could interact with D-clade type 2C protein phosphatase (PP2C) proteins to inhibit their phosphatase activities, therefore activating…”

Genetic Control of Plasticity in Root Morphology and Anatomy of Rice in Response to Water Deficit

“…For instance, one locus on chromosome 6 (366330) for RL0510 in control (Supplemental Table S9) was within the SCARECROW (SCR) gene that regulates radial root and shoot anatomy and root hair tip growth through cell division and differentiation (Gao et al, 2004). One locus on chromosome 1 (40526762) for RV in control was within the OsSAUR3 gene, an early auxin-responsive gene that regulates root elongation (Markakis et al, 2013). The two homologs of this gene were close (OsSAUR25 = 11 kb and OsSAUR26 = 42 kb) to the locus on chromosome 6 (27819933) for MRL in control (Supplemental Table S9).…”

SAUR Proteins as Effectors of Hormonal and Environmental Signals in Plant Growth

“…SAUR76 is highly expressed in roots, but only weakly expressed in leaves. Interestingly, while auxin treatment resulted in a dramatic upregulation in roots, no increase in SAUR76 expression was observed in leaves (Markakis et al, 2013). When overexpressed from the 35S promoter, SAUR76 conferred a reduction in leaf size.…”