Expression analysis of LIM gene family in poplar, toward an updated phylogenetic classification

Abstract

BackgroundPlant LIM domain proteins may act as transcriptional activators of lignin biosynthesis and/or as actin binding and bundling proteins. Plant LIM genes have evolved in phylogenetic subgroups differing in their expression profiles: in the whole plant or specifically in pollen. However, several poplar PtLIM genes belong to uncharacterized monophyletic subgroups and the expression patterns of the LIM gene family in a woody plant have not been studied.FindingsIn this work, the expression pattern of the twelve duplicated poplar PtLIM genes has been investigated by semi quantitative RT-PCR in different vegetative and reproductive tissues. As in other plant species, poplar PtLIM genes were widely expressed in the tree or in particular tissues. Especially, PtXLIM1a, PtXLIM1b and PtWLIM1b genes were preferentially expressed in the secondary xylem, suggesting a specific function in wood formation. Moreover, the expression of these genes and of the PtPLIM2a gene was increased in tension wood. Western-blot analysis confirmed the preferential expression of PtXLIM1a protein during xylem differentiation and tension wood formation. Genes classified within the pollen specific PLIM2 and PLIM2-like subgroups were all strongly expressed in pollen but also in cottony hairs. Interestingly, pairs of duplicated PtLIM genes exhibited different expression patterns indicating subfunctionalisations in specific tissues.ConclusionsThe strong expression of several LIM genes in cottony hairs and germinating pollen, as well as in xylem fibers suggests an involvement of plant LIM domain proteins in the control of cell expansion. Comparisons of expression profiles of poplar LIM genes with the published functions of closely related plant LIM genes suggest conserved functions in the areas of lignin biosynthesis, pollen tube growth and mechanical stress response. Based on these results, we propose a novel nomenclature of poplar LIM domain proteins.

Live cell imaging approaches reveal actin cytoskeleton-induced self-association of the actin-bundling protein WLIM1

“…in pollen tubes) requires factors other than LIM proteins: nucleators such as formins (Michelot et al, 2006) and/or other, more selective, actin-bundling proteins. Consistent with this hypothesis, plant LIM proteins are highly expressed in various types of cell (Arnaud et al, 2012;Eliasson et al, 2000;Papuga et al, 2010;Wang et al, 2008) and are accordingly expected to contribute to the formation of structurally different (unipolar and mixed polarity) bundles.…”

Identification and characterization of LIM gene family in Brassica rapa

“…Plant cells can detect mechanical stress on the epidermal cell surface and respond by reorganizing subcellular components like, actin microfilaments, endoplasmic reticulum (ER) and peroxisomes in a manner similar to that induced during attack by potential fungal or oomycete pathogens [ 58 ]. Expression analysis of poplar LIMs in tension wood also suggested a connection between plant LIMs and mechanical stress [ 59 ]. Thus, rearrangement of cytoskeletal elements through actin binding and bundling may also be the mechanism of abiotic stress responses of the CRP-like LIM genes.…”

The cotton XLIM protein (GhXLIM6) is required for fiber development via maintaining dynamic F‐actin cytoskeleton and modulating cellulose biosynthesis

“…It has been reported that XLIM subfamily proteins are preferentially expressed during xylem differentiation and tension wood formation (Déjardin et al ., ). In trees, tension wood is a peculiar cellulose‐rich and poorly lignified wood, suggesting XLIM subgroup proteins may be involved in regulating cellulose biosynthesis (Arnaud et al ., ). Similarly, more than 95% of mature cotton fiber mass is contributed by cellulose (Timpa and Triplett, ).…”