The N-end rule pathway promotes seed germination and establishment through removal of ABA sensitivity in Arabidopsis

Abstract

The N-end rule pathway targets protein degradation through the identity of the amino-terminal residue of specific protein substrates. Two components of this pathway in Arabidopsis thaliana, PROTEOLYSIS6 (PRT6) and arginyl-tRNA:protein arginyltransferase (ATE), were shown to regulate seed after-ripening, seedling sugar sensitivity, seedling lipid breakdown, and abscisic acid (ABA) sensitivity of germination. Sensitivity of prt6 mutant seeds to ABA inhibition of endosperm rupture reduced with after-ripening time, suggesting that seeds display a previously undescribed window of sensitivity to ABA. Reduced root growth of prt6 alleles and the ate1 ate2 double mutant was rescued by exogenous sucrose, and the breakdown of lipid bodies and seed-derived triacylglycerol was impaired in mutant seedlings, implicating the N-end rule pathway in control of seed oil mobilization. Epistasis analysis indicated that PRT6 control of germination and establishment, as exemplified by ABA and sugar sensitivity, as well as storage oil mobilization, occurs at least in part via transcription factors ABI3 and ABI5. The N-end rule pathway of protein turnover is therefore postulated to inactivate as-yet unidentified key component(s) of ABA signaling to influence the seed-to-seedling transition.abscisic acid ͉ aminoacyl tRNA protein transferase ͉ lipid bodies ͉ targeted protein degradation

A Shoot-Specific Hypoxic Response of Arabidopsis Sheds Light on the Role of the Phosphate-Responsive Transcription Factor PHOSPHATE STARVATION RESPONSE1

“…T-DNA insertions of the genes PHR1 (At4g28610; phr1-1, SALK_112862, containing a T-DNA insertion in intron 2 of PHR1; phr1-2, SALK_067629C, T-DNA insertion in exon 2 of PHR1) and PHL1 (At5g29000; SAIL_731_B09) in the Col-0 background were obtained from the Nottingham Arabidopsis Stock Centre. The N-end rule pathway mutants prt6 and ate1/ate2 have been described previously (Graciet et al, 2009;Holman et al, 2009), as well as photoreceptor mutants (phyA-211 phyB-9, Cerdán and Chory, 2003;phot1-5 phot2-1, de Carbonnel et al, 2010;cry2-1 cry1-304, Duek and Fankhauser, 2003).…”

“…Members of the group VII Ethylene Response Factor (ERF) family are processed by Met aminopeptidases, resulting in the exposure of an N-terminal Cys that can be oxidized enzymatically by plant cysteine oxidases (PCOs) depending on oxygen as a cosubstrate (Weits et al, 2014) and/or in a nitric oxide-dependent manner (Gibbs et al, 2014). This modified Cys makes the transcription factors accessible to the N-end rule pathway of protein degradation (Graciet et al, 2009;Holman et al, 2009;Weits et al, 2014). When oxygen becomes limiting, the group VII ERF transcription factors, such as Related to APETALA2.2 (RAP2.2) and RAP2.12, accumulate and activate hypoxia-responsive genes (Licausi et al, 2011).…”

The Putative E3 Ubiquitin Ligase ECERIFERUM9 Regulates Abscisic Acid Biosynthesis and Response during Seed Germination and Postgermination Growth in Arabidopsis

“…The keg mutation was found to suppress the ABA-insensitive phenotype of ABI5 in a seed germination assay (Stone et al, 2006). In addition, Arabidopsis PROTEOLYSIS6, a ubiquitin recognin box-containing E3 ligase associated with the N-end rule pathway of protein degradation, controls seed ABA sensitivity and seedling establishment (Holman et al, 2009).…”

ABI4 Activates DGAT1 Expression in Arabidopsis Seedlings during Nitrogen Deficiency

“…ABI4 is a crucial determinant of ABA sensitivity during TAG breakdown in the embryo (Penfield et al, 2006). ABI3 and ABI5, which encode B3 and basic-region Leu zipper-type transcription factors, respectively, participate in the repression of TAG degradation by close association with the N-end rule components PRT6 and ATE (Holman et al, 2009). In addition to the inhibitory effect on TAG degradation in plant seeds, ABA is also important for TAG accumulation.…”