TheArabidopsisDynamin-Related Protein2 Family Is Essential for Gametophyte Development  

Abstract

Clathrin-mediated membrane trafficking is critical for multiple stages of plant growth and development. One key component of clathrin-mediated trafficking in animals is dynamin, a polymerizing GTPase that plays both regulatory and mechanical roles. Other eukaryotes use various dynamin-related proteins (DRP) in clathrin-mediated trafficking. Plants are unique in the apparent involvement of both a family of classical dynamins (DRP2) and a family of dynamin-related proteins (DRP1) in clathrin-mediated membrane trafficking. Our analysis of drp2 insertional mutants demonstrates that, similar to the DRP1 family, the DRP2 family is essential for Arabidopsis thaliana development. Gametophytes lacking both DRP2A and DRP2B were inviable, arresting prior to the first mitotic division in both male and female gametogenesis. Mutant pollen displayed a variety of defects, including branched or irregular cell plates, altered Golgi morphology and ectopic callose deposition. Ectopic callose deposition was also visible in the pollen-lethal drp1c-1 mutant and appears to be a specific feature of pollen-defective mutants with impaired membrane trafficking. However, drp2ab pollen arrested at earlier stages in development than drp1c-1 pollen and did not accumulate excess plasma membrane or display other gross defects in plasma membrane morphology. Therefore, the DRP2 family, but not DRP1C, is necessary for cell cycle progression during early gametophyte development. This suggests a possible role for DRP2-dependent clathrin-mediated trafficking in the transduction of developmental signals in the gametophyte.

A role for Arabidopsis dynamin related proteins DRP2A/B in endocytosis; DRP2 function is essential for plant growth

“…Three insertions in DRP2A and two in DRP2B were identified (drp2a-1: SALK_071036; drp2a-3: SALK_011319; drp2a-4: SALK_018859; drp2b-1: SALK_ 003049; drp2b-6: SALK_150606. Allele names follow the nomenclature recently published by Backues et al 2010). Figure 1a shows the position of these insertions relative to the predicted intron/exon structure of the respective genes.…”

Clathrin Light Chains Regulate Clathrin-Mediated Trafficking, Auxin Signaling, and Development inArabidopsis

“…In plants, clathrin-dependent membrane trafficking is critical for a number of developmental processes, including the determination of cell polarity (Dhonukshe et al, 2008;Mravec et al, 2011), cytokinesis (Kang et al, 2003;Van Damme et al, 2011), cell elongation (Zhao et al, 2010), embryogenesis (Kitakura et al, 2011), and gametogenesis (Backues et al, 2010). Plant CLCs and CHCs predominantly localize to the PM and TGN/early endosome (EE) compartments (Dhonukshe et al, 2007;Konopka et al, 2008;Robert et al, 2010;Ito et al, 2012), and CME regulates the internalization of critical PM proteins involved in hormone signaling (Geldner et al, 2007;Robert et al, 2010;Xu et al, 2010;Irani et al, 2012), defense or stress responses (LeborgneCastel et al, 2008), and nutrient uptake (Barberon et al, 2011).…”

ACTIN DEPOLYMERIZING FACTOR4 Regulates Actin Dynamics during Innate Immune Signaling in Arabidopsis

“…To define this process, and to investigate whether the adf4 mutant had an altered transcriptional response to MAMP treatment compared with the wild type, we measured gene transcripts by quantitative RT-PCR for the MAPK and CDPK pathways ( Figure 6). After 1-h MAMP treatment, target gene transcripts of the MAPK signaling pathway (Backues et al, 2010;Boudsocq et al, 2010;Mao et al, 2011), including the MAPK-specific target gene FRK1 (Figure 6A), the MAPK-dominant gene CYP81F2 (Figure 6B), and a downstream indicator of MAPK signaling, WRKY33 ( Figure 6C; Boudsocq et al, 2010), were elevated in both wild-type and adf4 seedlings following treatment with both elf26 and chitin. This suggests that ADF4 and actin remodeling are not upstream of transcriptional activation in the MAPK-dependent pathway and is consistent with previous results showing that FRK1 responded normally to flg22 treatment of light-grown plants (Porter et al, 2012).…”

“…To test whether components of a MAMP receptor complex regulate actin filament abundance, we performed actin architecture analysis on several Arabidopsis knockout mutants that have disruptions in the EF-Tu signaling pathway (Figure 2). The bacterial MAMP elf26 is recognized by a plasma membrane-associated PRR complex, comprising the leucine-rich repeat-receptor kinases EF-Tu RECEPTOR (EFR) and BRI1-ASSOCIATED KINASE (BAK1) as well as the cytoplasmic kinase BOTRYTIS-INDUCED KINASE (BIK1) (Backues et al, 2010;Boudsocq et al, 2010;Mao et al, 2011;Zipfel et al, 2006). As expected, epidermal cells from wild-type plants and the fls2 mutant (lacking the PRR for flg22, FLS2) treated with elf26 for 5 min showed significantly enhanced filament abundance (Figure 2A).…”