A loss-of-function mutation in the nucleoporin AtNUP160 indicates that normal auxin signalling is required for a proper ethylene response in Arabidopsis

Abstract

As part of a continuing effort to elucidate mechanisms that regulate the magnitude of ethylene signalling, an Arabidopsis mutant with an enhanced ethylene response was identified. Subsequent characterization of this loss-of-function mutant revealed severe hypocotyl shortening in the presence of saturating ethylene along with increased expression in leaves of a subset of ethylene-responsive genes. It was subsequently determined by map-based cloning that the mutant (sar1-7) represents a loss-of-function mutation in the previously described nucleoporin AtNUP160 (At1g33410, SAR1). In support of previously reported results, the sar1-7 mutant partially restored auxin responsiveness to roots of an rce1 loss-of-function mutant, indicating that AtNUP160/SAR1 is required for proper expression of factors responsible for the repression of auxin signalling. Analysis of arf7-1/sar1-7 and arf19-1/sar1-7 double mutants revealed that mutations affecting either ARF7 or ARF19 function almost fully blocked manifestation of the sar1-7-dependent ethylene hypersensitivity phenotype, suggesting that ARF7- and ARF19-mediated auxin signalling is responsible for regulating the magnitude of and/or competence for the ethylene response in Arabidopsis etiolated hypocotyls. Consistent with this, addition of auxin to ethylene-treated seedlings resulted in severe hypocotyl shortening, reminiscent of that seen for other eer (enhanced ethylene response) mutants, suggesting that auxin functions in part synergistically with ethylene to control hypocotyl elongation and other ethylene-dependent phenomena.

Plant Growth Promoting Rhizobacterial Mitigation of Drought Stress in Crop Plants: Implications for Sustainable Agriculture

“…These phytohormones relieve plants from abiotic stresses and improve their survival rates [56,114,115]. There is an array of phytohormones, such as the cytokinins, auxins, gibberellins, ethylene, abscisic acid, and jasmonates, which either promote shoot growth or regulates growth-inhibitory processes in plants such as dormancy, abscission, and senescence, thereby controlling growth activities in plants [116][117][118]. Abscisic acid is vital to the opening and closing of the stomata, especially when plants are stressed.…”

Auxins as One of the Factors of Plant Growth Improvement by Plant Growth Promoting Rhizobacteria

“…The sites of action and production of these phytoregulators are generally quite distant from one another (Avanci et al, 2010;Liu et al, 2012). According to the classical view, five major classes of phytohormones are auxins, cytokinins, gibberellins, ethylene and abscisic acid (Jamil et al, 2012;Robles et al, 2012) but there is increasing evidence of other compounds to have shown growth regulating activities in plants. Among these are brassinosteroids, jasmonates, salicylic acid, strigolactones, etc.…”

“…Auxins, cytokinins, gibberellins and brassinosteroids promote shoot growth while others including ethylene, abscisic acid and jasmonates control growth activities by regulating growth inhibitory processes in plants such as dormancy, abscission, senescence etc. (Acosta and Farmer, 2010;Dempsey et al, 2011;Costigan et al, 2011;Liu et al, 2012;Robles et al, 2012).…”

“…3 262 coordinate regulation of various plant processes (Acosta and Farmer, 2010;Stewart and Nemhauser, 2010;Blomster et al, 2011;Koltai, 2011;Muller and Munne-Bosch, 2011;Chiu et al, 2012;Facella et al, 2012;Muday et al, 2012;Robles et al, 2012). Auxins and brassinosteroids have been found to interact with each other to regulate root development (Teale et al, 2008).…”

The CPR5-CKI signaling pathway plays a central role in integrating plant stress responses

“…The Nup proteins SUPPRESSOR OF AUXIN RESISTANCE 1 (SAR1, Nup160) and 3 (SAR3, Nup96) are required for the nuclear import of auxin (AUX) and (or) indole-3-acetic acid (IAA) proteins that are the repressors of auxin-inducible gene expressions (Parry et al 2006). SAR1 also mediates the ethylene signaling pathway (Robles et al 2012). The karyopherin protein MODIFIER OF SNC1, 6 (MOS6) and the Nup proteins MOS3 (Nup96) and MOS7 (Nup88) are crucial to the nuclear import of the key SA signaling regulator NON-EXPRESSER OF PR GENES 1 (NPR1) (Cheng et al 2009).…”