Arabidopsis plants deficient in constitutive class profilins reveal independent and quantitative genetic effects

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.

TWISTED DWARF1 Mediates the Action of Auxin Transport Inhibitors on Actin Cytoskeleton Dynamics

“…For instance, Rice Morphology Determinant, a type II formin, was shown to link auxin-actin regulation by influencing cell growth (Li et al, 2014). Moreover, recently, downregulation of the three vegetative profilins, PRF1-3, was reported to result in a drastic dwarfed phenotype resembling twd1 (Müssar et al, 2015). Finally, Arabidopsis vln2 vln3 and rice vln2 mutants show a twisted disorientation of organs (van der Honing et al, 2012;Wu et al, 2015).…”

Profilin-Dependent Nucleation and Assembly of Actin Filaments Controls Cell Elongation in Arabidopsis

“…In contrast, Meagher's group found that the prf1-1 mutant, which contains a T-DNA insertion in the promoter region of the PRF1 gene, has longer dark-grown hypocotyls and elevated organs (McKinney et al, 2001). Interestingly, another T-DNA insertion mutant in the first intron of PRF1 gene, prf1-4, results in light-grown seedlings and plants with a modest dwarfed phenotype (Müssar et al, 2015). These observations indicate that defects of PRF1 in Arabidopsis disrupt normal cell expansion and morphogenesis.…”

“…However, investigation of a prf1-1 mutant, which contains a T-DNA insertion in the promoter region of the PRF1 gene, indicates that cell expansion of seedlings is promoted and that protein levels of PRF1 are regulated by light (McKinney et al, 2001). Recently, Müssar et al (2015) reported a new Arabidopsis T-DNA insertion allele, prf1-4, that shows an obvious dwarf seedling phenotype. To date, however, there has not been a critical examination of the impact of the loss of profilin on the organization and dynamics of bona-fide single actin filaments in vivo.…”

Profilin Negatively Regulates Formin-Mediated Actin Assembly to Modulate PAMP-Triggered Plant Immunity

“…We examined Arabidopsis growth in wild-type (WT) and profilin mutants supplemented with bacterial flagellin peptide flg22 (QRLSTGSRINSAKDDAAGLQIA), which is recognized by a leucine-rich repeat receptor-like kinase FLS2 and trigger immune responses, which in turn causes an increase in actin filament density but a shortened plant [34,36]. Arabidopsis WT and the profilin mutants, prf1-2, prf1-4, and prf3 [37,38], were grown on 1/2 Murashige and Skoog (MS) medium agar plates and treated with flg22 at a concentration of 1 mM, or left untreated, for 7 days. The primary root length was measured and compared among all Arabidopsis seedlings ( Figures 4A and 4B).…”