Abstract
Members of the Arabidopsis (Arabidopsis thaliana) DYNAMIN-RELATED PROTEIN1 (DRP1) family are required for cytokinesis and cell expansion. Two isoforms, DRP1A and DRP1C, are required for plasma membrane maintenance during stigmatic papillae expansion and pollen development, respectively. It is unknown whether the DRP1s function interchangeably or if they have distinct roles during cell division and expansion. DRP1C was previously shown to form dynamic foci in the cell cortex, which colocalize with part of the clathrin endocytic machinery in plants. DRP1A localizes to the plasma membrane, but its cortical organization and dynamics have not been determined. Using dual color labeling with live cell imaging techniques, we showed that DRP1A also forms discreet dynamic foci in the epidermal cell cortex. Although the foci overlap with those formed by DRP1C and clathrin light chain, there are clear differences in behavior and response to pharmacological inhibitors between DRP1A and DRP1C foci. Possible functional or regulatory differences between DRP1A and DRP1C were supported by the failure of DRP1C to functionally compensate for the absence of DRP1A. Our studies indicated that the DRP1 isoforms function or are regulated differently during cell expansion.
Highlights
Members of the Arabidopsis (Arabidopsis thaliana) DYNAMIN-RELATED PROTEIN1 (DRP1) family are required for cytokinesis and cell expansion
One MtDRP1 and two OsDRP1s formed a clade with DRP1A, while one MtDRP1 and three OsDRP1s were more similar to DRP1C than to DRP1A
To determine if DRP1C and DRP1A are functionally redundant, we examined if expression of DRP1C under the control of the DRP1A promoter or constitutive expression using the viral promoter cauliflower mosaic virus 35S (35S) could complement the various phenotypes observed in drp1A-2 mutants. drp1A-2 plants are characterized by: (1) seedling lethality on soft agar (0.6% phytagar) plates, which can be rescued by supplementation with 1% Suc (Kang et al, 2001); (2) infertility due to the inability of their stigmatic papillae to undergo rapid polar expansion prior to fertilization (Kang et al, 2003a); (3) trichome branching defects (Kang et al, 2003a); and (4) defects in venation continuity in cotyledons (Sawa et al, 2005)
Summary
Members of the Arabidopsis (Arabidopsis thaliana) DYNAMIN-RELATED PROTEIN1 (DRP1) family are required for cytokinesis and cell expansion. DRP1A and DRP1C, are required for plasma membrane maintenance during stigmatic papillae expansion and pollen development, respectively. It is unknown whether the DRP1s function interchangeably or if they have distinct roles during cell division and expansion. The Arabidopsis DRP1 family is required during cytokinesis at the cell plate and during rapid cell expansion at the plasma membrane (Kang et al, 2001, 2003a, 2003b; Hong et al, 2003b; C.A. Konopka and S.Y. Bednarek, unpublished data). The relevance of this variable domain remains to be determined
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