Abstract
BackgroundRab proteins form the largest family of the Ras superfamily of small GTP-binding proteins and regulate intracellular trafficking pathways. However, the function of the Rab proteins in woody species is still an open question.ResultsHere, a total of 67 PtRabs were identified in Populus trichocarpa and categorized into eight subfamilies (RabA-RabH). Based on their chromosomal distribution and duplication blocks in the Populus genome, a total of 27 PtRab paralogous pairs were identified and all of them were generated by whole-genome duplication events. Combined the expression correlation and duplication date, the PtRab paralogous pairs that still keeping highly similar expression patterns were generated around the latest large-scale duplication (~ 13 MYA). The cis-elements and co-expression network of unique expanded PtRabs suggest their potential roles in poplar development and environmental responses. Subcellular localization of PtRabs from each subfamily indicates each subfamily shows a localization pattern similar to what is revealed in Arabidopsis but RabC shows a localization different from their counterparts. Furthermore, we characterized PtRabE1b by overexpressing its constitutively active mutant PtRabE1b(Q74L) in poplar and found that PtRabE1b(Q74L) enhanced the salt tolerance.ConclusionsThese findings provide new insights into the functional divergence of PtRabs and resources for genetic engineering resistant breeding in tree species.
Highlights
Rab proteins form the largest family of the Ras superfamily of small GTP-binding proteins and regulate intracellular trafficking pathways
A total of 67 putative Rab GTPase genes were identified in Populus (Additional file 1: Table S1)
Compared to Arabidopsis, four (RabA, RabC, RabD and RabF) of eight Rab subfamilies were extended in Populus
Summary
Rab proteins form the largest family of the Ras superfamily of small GTP-binding proteins and regulate intracellular trafficking pathways. Communication and transport between these membrane compartments are vital to basic cellular activities and development and environmental responses. This transport is maintained through complex and precise regulation pathways, which includes membrane fusion between transport vesicles and target organelles [2]. Rab GTPase are involved in the entire process of vesicle transport including budding from donor organelle, docking, tethering and fusing with the target membrane [3, 4]. There are four conserved motifs involved in nucleotide binding and hydrolysis in Rab proteins. Mutating the specific residues can generate dominant negative or constitutively active forms that exhibit altered nucleotide-binding or hydrolysis characteristics, which can be used to investigate Rab functions [1]
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