The MATH-BTB Protein TaMAB2 Accumulates in Ubiquitin-Containing Foci and Interacts With the Translation Initiation Machinery in Arabidopsis

Abstract

MATH-BTB proteins are known to act as substrate-specific adaptors of CUL3-based E3 ligases in the ubiquitin proteasome pathway. Their BTB domain binds to CUL3 scaffold proteins and the less conserved MATH domain targets a highly diverse collection of substrate proteins to promote their ubiquitination and subsequent degradation. In plants, a significant expansion of the MATH-BTB family occurred in the grasses. Here, we report analysis of TaMAB2, a MATH-BTB protein transiently expressed at the onset of embryogenesis in wheat. Due to difficulties in studying its role in zygotes and early embryos, we have overexpressed TaMAB2 in Arabidopsis to generate gain-of-function mutants and to elucidate interaction partners and substrates. Overexpression plants showed severe growth defects as well as disorganization of microtubule bundles indicating that TaMAB2 interacts with substrates in Arabidopsis. In tobacco BY-2 cells, TaMAB2 showed a microtubule and ubiquitin-associated cytoplasmic localization pattern in form of foci. Its direct interaction with CUL3 suggests functions in targeting specific substrates for ubiquitin-dependent degradation. Although direct interactions with tubulin could not be confimed, tandem affinity purification of TaMAB2 interactors point towards cytoskeletal proteins including tubulin and actin as well as the translation initiation machinery. The idenification of various subunits of eucaryotic translation initiation factors eIF3 and eIF4 as TaMAB2 interactors indicate regulation of translation initiation as a major function during onset of embryogenesis in plants.

The New Is Old: Novel Germination Strategy Evolved From Standing Genetic Variation in Weedy Rice

“…The function of other genes harboring potentially adaptive “weedy” alleles have not yet been well-characterized, but all the four genes subjected to genotyping and validation by qRT-PCR were predicted to be involved in response to abiotic stress based on GO annotations. Os08g0227200 encoded an MATH-BTB domain containing protein which could act as a substrate-specific adaptor to bind with the E3 ubiquitin ligase component Cullin-3 to target protein for ubiquitination (Bauer et al, 2019 ). Juranić and Dresselhaus ( 2014 ) reported an expanded and highly divergent group of MATH-BTB proteins in different grass species.…”

Puncta‐localized TRAF domain protein TC1b contributes to the autoimmunity of snc1

“…Further colocalization experiments, particularly with markers for membraneless organelles, may provide clues for its function. Interestingly, the wheat ( Triticum aestivum ) TRAF‐BTB protein Ta MAB2 localizes to cytoplasmic foci in Arabidopsis protoplasts, and overexpression of Ta MAB2 leads to growth defects resembling autoimmune mutants (Bauer et al., 2019). In addition, the maize ( Zea mays ) TRAF‐BTB Zm MAB1 localizes to speckles in the nucleus and cytoplasm of tobacco suspension cells, which is dependent on the cell cycle stage (Juranič et al., 2012).…”

Genome-Wide Identification of BTB Domain-Containing Gene Family in Grapevine (Vitis vinifera L.)

“…According to some recent reports, the BTB domain plays plausible roles in developmental and stress-related pathways in several plants [6,7,12,13,[20][21][22]24,26,54,55]. Moreover, the availability of significant genomic and transcriptomic data of wine grapes encouraged us to attempt the genome-wide identification and characterization of the recently identified BTB domain containing a protein family.…”

“…Likewise, the BT2 protein regulates plants' responses towards ABA and sugars by interacting with two global transcription factor group E proteins (GTE9 and GTE11), and BT1 and BT2 are also known to play crucial roles in nitrate responses by direct activation through NLP transcription activators [14][15][16]. In addition, the BT2 protein also regulates telomerase activity in vegetative organs and is suggested to be a component of several interconnected networks [17][18][19][20]. MdBT2 also delays leaf senescence by interacting with the MdbHLH93 protein in apple [21].…”