The Arabidopsis paralogs, PUB46 and PUB48, encoding U-box E3 ubiquitin ligases, are essential for plant response to drought stress

Abstract

BackgroundPlants respond to abiotic stress on physiological, biochemical and molecular levels. This includes a global change in their cellular proteome achieved by changes in the pattern of their protein synthesis and degradation. The ubiquitin-proteasome system (UPS) is a key player in protein degradation in eukaryotes. Proteins are marked for degradation by the proteasome by coupling short chains of ubiquitin polypeptides in a three-step pathway. The last and regulatory stage is catalyzed by a member of a large family of substrate-specific ubiquitin ligases.ResultsWe have identified AtPUB46 and AtPUB48—two paralogous genes that encode ubiquitin ligases (E3s)—to have a role in the plant environmental response. The AtPUB46, −47, and −48 appear as tandem gene copies on chromosome 5, and we present a phylogenetic analysis that traces their evolution from an ancestral PUB-ARM gene. Single homozygous T-DNA insertion mutants of AtPUB46 and AtPUB48 displayed hypersensitivity to water stress; this was not observed for similar mutants of AtPUB47. Although the three genes show a similar spatial expression pattern, the steady state levels of their transcripts are differentially affected by abiotic stresses and plant hormones.Conclusions AtPUB46 and AtPUB48 encode plant U-Box E3s and are involved in the response to water stress. Our data suggest that despite encoding highly homologous proteins, AtPUB46 and AtPUB48 biological activity does not fully overlap.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0963-5) contains supplementary material, which is available to authorized users.

Overexpression of Arabidopsis ubiquitin ligase AtPUB46 enhances tolerance to drought and oxidative stress

“…Furthermore, ABA, the plant hormone related to abiotic stresses such as water-, osmotic-and saltstresses (for a recent review see [38]) did not affect the sensitivity to inhibition of germination and greening of AtPUB46-OE plants, indicating that the NaCl response is not mediated by osmotic stress or ABA. Interestingly, ABA also does not affect the steady state levels of AtPUB46-transcripts [11].…”

“…AtPUB46 is involved in the plant response to abiotic stress T-DNA insertion Atpub46 mutants are hypersensitive to drought stress and water withholding affects their photosynthesis efficiency compared with WT plants [11]. These findings indicate a major role for AtPUB46 in plant drought tolerance [11].…”

“…We recently reported that the Arabidopsis E3, Plant U-box 46 (AtPUB46), is involved in the response to abiotic stress [11]. The PUB family of monomeric U-box proteins comprise a ~70 amino acid RING-like motif [8,12,13] followed by 3 non-identical repeats of the Armadillo (ARM) motif, shown to function in protein-protein interactions [14,15].…”

“…The PUB family of monomeric U-box proteins comprise a ~70 amino acid RING-like motif [8,12,13] followed by 3 non-identical repeats of the Armadillo (ARM) motif, shown to function in protein-protein interactions [14,15]. AtPUB46 is expressed in both roots and shoots [11]. AtPUB46 transcript levels are modulated by abiotic stress: salt stress elevates its transcript levels in both roots and shoots, and osmotic stress enhances levels in the shoots.…”

Decoys provide a scalable platform for the genetic analysis of plant E3 ubiquitin ligases that regulate circadian clock function

“…PUB48, like PUB30, contains two ARM repeats and has a partially redundant homolog, PUB46 (Table 3) (Adler et al, 2017). PUB48 expression is not rhythmic under diurnal cycles.…”