Abstract
Rapid response to environmental changes and abiotic stress to coordinate developmental programs is critical for plants. To accomplish this, plants use the ubiquitin proteasome pathway as a flexible and efficient mechanism to control protein stability and to direct cellular reactions. Here, we show that all three members of the R2R3 S23 MYB transcription factor subfamily, MYB1, MYB25, and MYB109, are degraded by the 26S proteasome, likely facilitated by a CUL3-based E3 ligase that uses MATH-BTB/POZ proteins as substrate adaptors. A detailed description of MYB1, MYB25, and MYB109 expression shows their nuclear localization and specific tissue specific expression patterns. It further demonstrates that elevated expression of MYB25 reduces sensitivities toward abscisic acid, osmotic and salt stress in Arabidopsis, while downregulation of all S23 members results in hypersensitivities. Transcriptional profiling in root and shoot of seedlings overexpressing MYB25 shows that the transcription factor widely affects cellular stress pathways related to biotic and abiotic stress control. Overall, the work extends our knowledge on proteins targeted by CUL3-based E3 ligases that use MATH-BTB/POZ proteins as substrate adaptors and provides first information on all members of the MYB S23 subfamily.
Highlights
The control of protein stability is a central tool for plants to quickly respond to environmental changes, and to efficiently coordinate developmental and physiological processes
We provide novel information about the MYB R2R3 S23 subfamily members MYB1, MYB25, and MYB109, with a closer focus on MYB25
We demonstrate for all three members tissue specific expression patterns and subcellular localization, that all three S23 members assemble with the Arabidopsis BPM family, and that they can be degraded by the 26S proteasome in cell-free degradation assays
Summary
The control of protein stability is a central tool for plants to quickly respond to environmental changes, and to efficiently coordinate developmental and physiological processes. A key regulatory mechanism to accomplish this is the ubiquitin proteasome pathway, which marks selected proteins with ubiquitins (UBQ) (Choi et al, 2014) This process utilizes an E3 ligase to bind with a substrate, facilitating its ubiquitylation. Arabidopsis expresses six BPM proteins and so far, all identified substrates have been transcription factors, and include members from four major families: R2R3 myeloblastosis (MYB), APETALA2/ERF binding factors (AP2/ERF), myelocytoma (MYC) and class I homeobox-leucine zipper (HB) (Weber et al, 2005; Weber and Hellmann, 2009; Lechner et al, 2011; Chen et al, 2013, 2015; Mooney et al, 2019; Chico et al, 2020)
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