UPL1 and 2, two 405 kDa ubiquitin-protein ligases from Arabidopsis thaliana related to the HECT-domain protein family

Abstract In flowering plants, repression of the seed maturation program is essential for the transition from the seed to the vegetative phase, but the underlying mechanisms remain poorly understood. The B3-domain protein VIVIPAROUS1/ABSCISIC ACID-INSENSITIVE3-LIKE 1 (VAL1) is involved in repressing the seed maturation program. Here we uncovered a molecular network triggered by the plant hormone brassinosteroid (BR) that inhibits the seed maturation program during the seed-to-seedling transition in Arabidopsis (Arabidopsis thaliana). val1-2 mutant seedlings treated with a BR biosynthesis inhibitor form embryonic structures, whereas BR signaling gain-of-function mutations rescue the embryonic structure trait. Furthermore, the BR-activated transcription factors BRI1-EMS-SUPPRESSOR 1 and BRASSINAZOLE-RESISTANT 1 bind directly to the promoter of AGAMOUS-LIKE15 (AGL15), which encodes a transcription factor involved in activating the seed maturation program, and suppress its expression. Genetic analysis indicated that BR signaling is epistatic to AGL15 and represses the seed maturation program by downregulating AGL15. Finally, we showed that the BR-mediated pathway functions synergistically with the VAL1/2-mediated pathway to ensure the full repression of the seed maturation program. Together, our work uncovered a mechanism underlying the suppression of the seed maturation program, shedding light on how BR promotes seedling growth.

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Arabidopsis thaliana G3BP Ortholog Rescues Mammalian Stress Granule Phenotype across Kingdoms

International Journal of Molecular Sciences ◽

10.3390/ijms22126287 ◽

2021 ◽

Vol 22 (12) ◽

pp. 6287

Author(s):

Hendrik Reuper ◽

Benjamin Götte ◽

Lucy Williams ◽

Timothy J. C. Tan ◽

Gerald M. McInerney ◽

...

Keyword(s):

Arabidopsis Thaliana ◽

Fusion Proteins ◽

Biological Function ◽

Protein Complexes ◽

Protein Family ◽

Knock Out ◽

Marker Proteins ◽

Interaction Partners ◽

Functional Analyses ◽

Rna Protein Complexes

Stress granules (SGs) are dynamic RNA–protein complexes localized in the cytoplasm that rapidly form under stress conditions and disperse when normal conditions are restored. The formation of SGs depends on the Ras-GAP SH3 domain-binding protein (G3BP). Formations, interactions and functions of plant and human SGs are strikingly similar, suggesting a conserved mechanism. However, functional analyses of plant G3BPs are missing. Thus, members of the Arabidopsis thaliana G3BP (AtG3BP) protein family were investigated in a complementation assay in a human G3BP knock-out cell line. It was shown that two out of seven AtG3BPs were able to complement the function of their human homolog. GFP-AtG3BP fusion proteins co-localized with human SG marker proteins Caprin-1 and eIF4G1 and restored SG formation in G3BP double KO cells. Interaction between AtG3BP-1 and -7 and known human G3BP interaction partners such as Caprin-1 and USP10 was also demonstrated by co-immunoprecipitation. In addition, an RG/RGG domain exchange from Arabidopsis G3BP into the human G3BP background showed the ability for complementation. In summary, our results support a conserved mechanism of SG function over the kingdoms, which will help to further elucidate the biological function of the Arabidopsis G3BP protein family.

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The putatively protective Onchocerca volvulus neuronal protein E1 is a member of the death domain protein family

FEBS Letters ◽

10.1016/0014-5793(96)00620-5 ◽

1996 ◽

Vol 390 (1) ◽

pp. 21-24 ◽

Cited By ~ 2

Author(s):

K.D. Erttmann ◽

A. Domeyer ◽

M. Gallin

Keyword(s):

Protein Family ◽

Onchocerca Volvulus ◽

Death Domain ◽

Neuronal Protein ◽

Domain Protein

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Manganese toxicity and Saccharomyces cerevisiae Mam3p, a member of the ACDP (ancient conserved domain protein) family

Biochemical Journal ◽

10.1042/bj20041582 ◽

2005 ◽

Vol 386 (3) ◽

pp. 479-487 ◽

Cited By ~ 23

Author(s):

Mei YANG ◽

Laran T. JENSEN ◽

Allison J. GARDNER ◽

Valeria C. CULOTTA

Keyword(s):

Saccharomyces Cerevisiae ◽

Integral Membrane Protein ◽

Manganese Toxicity ◽

Protein Family ◽

Neurological Deficits ◽

Yeast Saccharomyces Cerevisiae ◽

Conserved Domain ◽

Genetic Epistasis ◽

Accumulation Of Metals ◽

Domain Protein

Manganese is an essential, but potentially toxic, trace metal in biological systems. Overexposure to manganese is known to cause neurological deficits in humans, but the pathways that lead to manganese toxicity are largely unknown. We have employed the bakers' yeast Saccharomyces cerevisiae as a model system to identify genes that contribute to manganese-related damage. In a genetic screen for yeast manganese-resistance mutants, we identified S. cerevisiae MAM3 as a gene which, when deleted, would increase cellular tolerance to toxic levels of manganese and also increased the cell's resistance towards cobalt and zinc. By sequence analysis, Mam3p shares strong similarity with the mammalian ACDP (ancient conserved domain protein) family of polypeptides. Mutations in human ACDP1 have been associated with urofacial (Ochoa) syndrome. However, the functions of eukaryotic ACDPs remain unknown. We show here that S. cerevisiae MAM3 encodes an integral membrane protein of the yeast vacuole whose expression levels directly correlate with the degree of manganese toxicity. Surprisingly, Mam3p contributes to manganese toxicity without any obvious changes in vacuolar accumulation of metals. Furthermore, through genetic epistasis studies, we demonstrate that MAM3 operates independently of the well-established manganese-trafficking pathways in yeast, involving the manganese transporters Pmr1p, Smf2p and Pho84p. This is the first report of a eukaryotic ACDP family protein involved in metal homoeostasis.

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