Trans-Golgi network localized small GTPase RabA1d is involved in cell plate formation and oscillatory root hair growth

Abstract

BackgroundSmall Rab GTPases are important regulators of vesicular trafficking in plants. AtRabA1d, a member of the RabA1 subfamily of small GTPases, was previously found in the vesicle-rich apical dome of growing root hairs suggesting a role during tip growth; however, its specific intracellular localization and role in plants has not been well described.ResultsThe transient expression of 35S::GFP:RabA1d construct in Allium porrum and Nicotiana benthamiana revealed vesicular structures, which were further corroborated in stable transformed Arabidopsis thaliana plants. GFP-RabA1d colocalized with the trans-Golgi network marker mCherry-VTI12 and with early FM4-64-labeled endosomal compartments. Late endosomes and endoplasmic reticulum labeled with FYVE-DsRed and ER-DsRed, respectively, were devoid of GFP-RabA1d. The accumulation of GFP-RabA1d in the core of brefeldin A (BFA)-induced-compartments and the quantitative upregulation of RabA1d protein levels after BFA treatment confirmed the association of RabA1d with early endosomes/TGN and its role in vesicle trafficking. Light-sheet microscopy revealed involvement of RabA1d in root development. In root cells, GFP-RabA1d followed cell plate expansion consistently with cytokinesis-related vesicular trafficking and membrane recycling. GFP-RabA1d accumulated in disc-like structures of nascent cell plates, which progressively evolved to marginal ring-like structures of the growing cell plates. During root hair growth and development, GFP-RabA1d was enriched at root hair bulges and at the apical dome of vigorously elongating root hairs. Importantly, GFP-RabA1d signal intensity exhibited an oscillatory behavior in-phase with tip growth. Progressively, this tip localization dissapeared in mature root hairs suggesting a link between tip localization of RabA1d and root hair elongation. Our results support a RabA1d role in events that require vigorous membrane trafficking.ConclusionsRabA1d is located in early endosomes/TGN and is involved in vesicle trafficking. RabA1d participates in both cell plate formation and root hair oscillatory tip growth. The specific GFP-RabA1d subcellular localization confirms a correlation between its specific spatio-temporal accumulation and local vesicle trafficking requirements during cell plate and root hair formation.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-014-0252-0) contains supplementary material, which is available to authorized users.

Advances in Imaging Plant Cell Dynamics

“…LSFM also allowed the precise characterization of cell division patterns during the formation and growth of Arabidopsis lateral roots (von Wangenheim et al, 2016). Another important advantage of LSFM for dynamic developmental studies of plants is deep imaging of nuclei (Novák et al, 2016) and endosomes (Berson et al, 2014) in inner root tissues and the undisturbed development of root hairs (Fig. 6, E-I).…”

“…By using LSFM, it is possible to monitor the growth of root hairs from their initiation to full differentiation but also to track fastmoving organelles such as endosomes and correlate their dynamics to the pattern of root hair elongation (Fig. 6, H and I;Berson et al, 2014). Moreover, LSFM was combined recently with Förster resonance energy transfer (FRET) to address the respiration rates of root hairs using a FRET sensor for MgATP production (De Col et al, 2017).…”

ENDOSOMAL RAB EFFECTOR WITH PX-DOMAIN, an Interacting Partner of RAB5 GTPases, Regulates Membrane Trafficking to Protein Storage Vacuoles in Arabidopsis

“…The unique organization of endosomal trafficking in plants is also demonstrated by the observation that the trans-Golgi network (TGN) acts as an early endosome in plants (Dettmer et al, 2006;Lam et al, 2007;Viotti et al, 2010), from which multivesicular endosomes are proposed to be directly generated by maturation (Niemes et al, 2010;Scheuring et al, 2011). The RAB11 group (also known as RABA in Arabidopsis), which is localized to TGNrelated secretory compartments and is involved in cell plate formation and tip growth (Preuss et al, 2004;Chow et al, 2008;Szumlanski and Nielsen, 2009;Kang et al, 2011;Feraru et al, 2012;Asaoka et al, 2013;Berson et al, 2014;Kirchhelle et al, 2016), is also implicated in endosomal/vacuolar trafficking (Bottanelli et al, 2011;Choi et al, 2013). These lines of evidence indicate that endosomal trafficking in plant cells operates in a different manner from that in non-plant organisms.…”

Subcellular localizations of Arabidopsis myotubularins MTM1 and MTM2 suggest possible functions in vesicular trafficking between ER and cis-Golgi

“…The following Tans Golgi Network (TGN) markers were used: syntaxins of plants (SYP61-GFP) which is mainly localized to TGN (Sanderfoot et al, 2000(Sanderfoot et al, , 2001. VTI12-YFP is one of the Arabidopsis homolog of the yeast SNARE Vti1p (Zheng et al, 1999); RabA1d-GFP is a member of the RabA subfamily of small Rab GTPases which is one of the reliable marker used for studying secretory/recycling vesicles (Berson et al, 2014). G-YK is a cis-Golgi marker based on the targeting sequence of soybean alpha-1,2 mannosidase I (a cisGolgi enzyme) (Nelson et al, 2007).…”