Abstract
BackgroundThe actin cytoskeleton is involved in an array of integral structural and developmental processes throughout the cell. One of actin’s best-studied binding partners is the small ubiquitously expressed protein, profilin. Arabidopsis thaliana is known to encode a family of five profilin sequence variants: three vegetative (also constitutive) profilins that are predominantly expressed in all vegetative tissues and ovules, and two reproductive profilins that are specifically expressed in pollen. This paper analyzes the roles of the three vegetative profilin members, PRF1, PRF2, and PRF3, in plant cell and organ development.ResultsUsing a collection of knockout or severe knockdown T-DNA single mutants, we found that defects in each of the three variants gave rise to specific developmental deficiencies. Plants lacking PRF1 or PRF2 had defects in rosette leaf morphology and inflorescence stature, while those lacking PRF3 led to plants with slightly elongated petioles. To further examine these effects, double mutants and double and triple gene-silenced RNAi epialleles were created. These plants displayed significantly compounded developmental defects, as well as distinct lateral root growth morphological phenotypes.ConclusionThese results suggest that having at least one vegetative profilin gene is essential to viability. Evidence is presented that combinations of independent function, quantitative genetic effects, and functional redundancy have preserved the three vegetative profilin genes in the Arabidopsis lineage.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0551-0) contains supplementary material, which is available to authorized users.
Highlights
The actin cytoskeleton is involved in an array of integral structural and developmental processes throughout the cell
The prf1-4 allele has an insertion in the first intron 74 bp upstream of the second exon, prf2-1 has an insertion 113 bp upstream of the translational start site in the promoter, and prf3-2 has an insertion at the end of the first exon (Fig. 1a)
To ensure that the resulting mutant phenotypes were caused by these specific insertions, we constructed lines that were complemented by overexpressing endogenous PRF1, PRF2 or PRF3 cDNAs, respectively, under the control of the constitutive Actin2 promoter and terminator (A2pt)
Summary
The actin cytoskeleton is involved in an array of integral structural and developmental processes throughout the cell. Actin Binding Proteins (ABPs) facilitate rapid remodeling of the actin cytoskeleton by regulating the unpolymerized (G-actin monomers) and polymerized (F-actin filaments) actin (ACT) equilibrium [1]. Actin-ABP interactions regulate such processes as stress response, cell signaling, transcription, cytokineses, cell locomotion, organelle positioning and movement, nuclear transport, maintenance of cell size, shape, and polarity, and organ development [2,3,4,5,6,7,8]. Profilins (PRFs) are small (12–15 kDa), ubiquitously expressed, monomeric ABPs that have been identified in organisms ranging from most protists and all fungi to all higher plants and animals examined [9]. Profilin was shown to bind G-actin (globular actin) and was thought primarily responsible for G-actin sequestering in cells [10]. Once actin barbed ends (+ end of actin polarity) become blocked by capping proteins, profilin begins to sequester G-actin from pointed-end polymerization [11]
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