Upstream Open Reading Frame Mediated Translation of WNK8 Is Required for ABA Response in Arabidopsis

Abstract

With no lysine (K) (WNK) kinases comprise a family of serine/threonine kinases belonging to an evolutionary branch of the eukaryotic kinome. These special kinases contain a unique active site and are found in a wide range of eukaryotes. The model plant Arabidopsis has been reported to have 11 WNK members, of which WNK8 functions as a negative regulator of abscisic acid (ABA) signaling. Here, we found that the expression of WNK8 is post-transcriptionally regulated through an upstream open reading frame (uORF) found in its 5′ untranslated region (5′-UTR). This uORF has been predicted to encode a conserved peptide named CPuORF58 in both monocotyledons and dicotyledons. The analysis of the published ribosome footprinting studies and the study of the frameshift CPuORF58 peptide with altered repression capability suggested that this uORF causes ribosome stalling. Plants transformed with the native WNK8 promoter driving WNK8 expression were comparable with wild-type plants, whereas the plants transformed with a similar construct with mutated CPuORF58 start codon were less sensitive to ABA. In addition, WNK8 and its downstream target RACK1 were found to synergistically coordinate ABA signaling rather than antagonistically modulating glucose response and flowering in plants. Collectively, these results suggest that the WNK8 expression must be tightly regulated to fulfill the demands of ABA response in plants.

CRISPR-Cas-mediated unfolded protein response control for enhancing plant stress resistance

“…The uORFs are essential regulatory elements located in the 5’ UTR of main open reading frames (mORFs). Recent bioinformatics analyses estimate that approximately 35% of total plant transcripts contain uORFs ( Silva et al., 2019 ; Li et al., 2021 ). These uORFs are known to act as inhibitors, repressing the initiation of mORF translation via ribosome stalling ( Silva et al., 2019 ; Zhang et al., 2020 ).…”

Advances in the Molecular Mechanisms of Abscisic Acid and Gibberellins Functions in Plants 2.0

“…These works cover outstanding advances in the molecular mechanisms by which GA and ABA control different aspects of plant physiology, development and for ABA, also in the response to abiotic stresses. In line with this, the original research articles investigate the effects of ABA on epicuticular wax metabolism regulation in a citrus fruit cultivar [ 9 ], the regulation of WNK kinases and their comprehensive interaction with ABA components [ 10 ], CCD family members in poplar and their expression patterns in response to ABA and abiotic stress [ 11 ], the molecular function of NAC transcription factor PwNAC11 in drought stress [ 12 ], the interaction between AFPs and DELLA proteins [ 13 ], and the molecular mechanism by which AGB1 regulates the GA pathway in Arabidopsis [ 14 ]. The reviews published in this Special Issue focus on how ABA regulates plant development and stress tolerance through alternative splicing [ 15 ], the mechanisms of ABA-mediated drought stress responses in plants [ 16 ], the roles of ABA and GA in stem/root tuber development [ 17 ] and the molecular mechanisms underlying ABA and GA regulation of seed development from embryogenesis to maturation [ 18 ].…”

“…Interestingly, the presence of a conserved peptide encoded by an upstream open reading frame (uORF) called CPuORF58 has been reported in the 5′-UTR of WNK8 [ 20 ]. Li et al [ 10 ] thoroughly studied WNK8 regulation and interaction with ABA components. They indicated that WNK8 negatively regulates ABA response during seed germination and post-germination development.…”

“…Furthermore, WNK8 and its downstream target RACK1 (receptor for activated C kinase1) synergistically coordinate ABA signaling. Li et al [ 10 ] concluded that WNK8 post-transcriptional regulation by the CPuORF58 conserved peptide located in its 5′-UTR is required for accomplishing plant ABA requirements.…”