PpRab1, a Rab GTPase from maritime pine is differentially expressed during embryogenesis

Abstract

Rab-related small GTP-binding proteins are known to be involved in the regulation of the vesicular transport system in eukaryotic cells. We report the characterization of a previously isolated full-length cDNA PpRab1 from Pinus pinaster. Amino acid sequence analysis revealed the presence of G1-G5 conserved domains of the GTPase Ras superfamily and a double cysteine motif in the C-terminal, characteristic of Rab proteins. The PpRab1 protein shows high sequence similarity to several Rab1 GTP-binding proteins in plants. Phylogenetic analysis showed that, within the Ras superfamily, PpRab1 is more closely related to the Rab family and within this, PpRab1 protein was found to cluster with Arabidopsis subfamily AtRABE, whose members are known to regulate ER-to-Golgi membrane trafficking steps. PpRab1 transcripts were expressed at constitutively high levels for the initial stages of zygotic embryo development, and then their relative abundance decreased as embryo matures. The PpRab1 transcript is not embryo-specific as it was found in roots, cotyledons and hypocotyls. An increase in PpRab1 expression level was observed when seeds are germinated and collected at successive time points of development. In situ RT-PCR analysis revealed an expression signal in early zygotic embryos. In view of the proposed roles of Rab1 GTP-binding protein, the possible function of the protein encoded by PpRab1 in embryogenesis is discussed.

New Putative Chloroplast Vesicle Transport Components and Cargo Proteins Revealed Using a Bioinformatics Approach: An Arabidopsis Model

“…Rab2 is also involved in the maturation of vesicular tubular clusters (VTCs), which are microtubule-associated intermediates in transport between the ER and Golgi apparatus [182]. AtRabB1C could be involved in retrograde or anterograde transport between the ER and Golgi, it has been localized in the ER and Golgi apparatus [183], and shown to have a role in early embryogenesis in plants [184].…”

Insights into the conversion potential of Theobroma cacao L. somatic embryos using quantitative proteomic analysis

“…In addition, it has been evidenced that Rab GTPases expression is modulated in response to variations in levels of phytohormones such as ethylene (Moshkov et al, 2003) and abscisic acid during plant development and germinating seedlings (Cui et al, 2013;Nishimura, 2004). In maritime pine embryogenesis, RAB GTPases were expressed in early stages of embryo development; the transcript was detected in early developmental stages of zygotic embryogenesis and the amount of transcript was progressively reduced in later stages (Gonçalves et al, 2007;Tzafrir et al, 2002).…”

The Regulatory RAB and ARF GTPases for Vesicular Trafficking

“…This and the accumulation of an endoglycosidase H-sensitive population of the Golgitargeted GFP confirmed that trafficking from ER to the Golgi was inhibited in cells compromised in their RAB1-regulated trafficking activity as a result of DN RAB1b overexpression. Developmentally, a recent study in maritime pine (Pinus pinaster) revealed high levels of expression of a RAB1, PpRAB1, in early zygotic development followed by decline as embryos matured, suggesting a role for this small GTPase in early embryogenesis (Goncalves et al, 2007).…”