ANGUSTIFOLIA, a Plant Homolog of CtBP/BARS Localizes to Stress Granules and Regulates Their Formation

Abstract

The ANGUSTIFOLIA (AN) gene in Arabidopsis is important for a plethora of morphological phenotypes. Recently, AN was also reported to be involved in responses to biotic and abiotic stresses. It encodes a homolog of the animal C-terminal binding proteins (CtBPs). In contrast to animal CtBPs, AN does not appear to function as a transcriptional co-repressor and instead functions outside nucleus where it might be involved in Golgi-associated membrane trafficking. In this study, we report a novel and unexplored role of AN as a component of stress granules (SGs). Interaction studies identified several RNA binding proteins that are associated with AN. AN co-localizes with several messenger ribonucleoprotein granule markers to SGs in a stress dependent manner. an mutants exhibit an altered SG formation. We provide evidence that the NAD(H) binding domain of AN is relevant in this context as proteins carrying mutations in this domain localize to a much higher degree to SGs and strongly reduce AN dimerization and its interaction with one interactor but not the others. Finally, we show that AN is a negative regulator of salt and osmotic stress responses in Arabidopsis suggesting a functional relevance in SGs.

ANGUSTIFOLIA Regulates Actin Filament Alignment for Nuclear Positioning in Leaves

“…AN encodes a plant homolog of C-terminal-binding protein/brefeldin A-ADP ribosylated substrate (CtBP/BARS; Folkers et al, 2002;Kim et al, 2002). AN is involved in determining leaf and cell shapes, root formation, microtubule organization, and abiotic stress responses in Arabidopsis (Tsuge et al, 1996;Folkers et al, 2002;Kim et al, 2002;Bai et al, 2013;Gachomo et al, 2013;Bhasin and Hülskamp, 2017). Our findings reveal the relationship between AN and the actin cytoskeleton in centripetal nuclear positioning in Arabidopsis leaves.…”

“…We identified DYRKP-2B as an AN-interacting protein (Fig. 8); its homolog DYRKP-1 also interacts physically with AN (Bhasin and Hülskamp, 2017). DYRKP-1 and DYRKP-2B are members of a plant-specific subgroup in the DYRK family (Kajikawa et al, 2015), which is widely conserved in animals, plants, fungi, and protists, and is involved in developmental processes, cell homeostasis, and cellular stresses (Aranda et al, 2011).…”

“…DYRKP-1 and DYRKP-2B are members of a plant-specific subgroup in the DYRK family (Kajikawa et al, 2015), which is widely conserved in animals, plants, fungi, and protists, and is involved in developmental processes, cell homeostasis, and cellular stresses (Aranda et al, 2011). DYRK3 is involved in stress granule formation in HeLa cells (Wippich et al, 2013), and AN is involved in this process in Arabidopsis leaf cells (Bhasin and Hülskamp, 2017), suggesting that DYRK3 and AN function in the same pathway. Given that DYRKPs had a high Mascot score in mass spectrometry analysis (Fig.…”

The ArathEULS3 Lectin Ends up in Stress Granules and Can Follow an Unconventional Route for Secretion

“…Interestingly, ANGUSTIFOLIA, which localizes to stress granules and regulates stress granules formation, was shown to interact also with the Glycine-rich RNA-binding protein 7. The latter protein might therefore be casual to the common localization of ANGUSTIFOLIA and ArathEULS3 in the stress granules [8]. All this evidence suggests that, even if ArathEULS3 does not bind directly to nucleic acids, it could be a part of a larger protein complex together with the Glycine-rich RNA-binding protein, which regulates transcription processes.…”

Function, localization and evolution of SOSEKI polar proteins

“…So far, nothing has been published about the biological role of SIK1-3. A recent study also showed interaction between SIK1 (AIK1) and AN in a yeast-twohybrid assay (Bhasin & Hülskamp, 2017). SIK1 to 3 are part of the Dual-specificity tyrosine-regulated kinases (DYRK) protein kinase family of which only one member has been studied in plants (Shiu et al, 2004).…”