Cell-to-cell movement of the CAPRICE protein in Arabidopsis root epidermal cell differentiation.
CAPRICE (CPC), a small, R3-type Myb-like protein, is a positive regulator of root hair development in Arabidopsis. Cell-to-cell movement of CPC is important for the differentiation of epidermal cells into trichoblasts (root hair cells). CPC is transported from atrichoblasts (hairless cells), where it is expressed, to trichoblasts, and generally accumulates in their nuclei. Using truncated versions of CPC fused to GFP, we identified a signal domain that is necessary and sufficient for CPC cell-to-cell movement. This domain includes the N-terminal region and a part of the Myb domain. Amino acid substitution experiments indicated that W76 and M78 in the Myb domain are critical for targeted transport, and that W76 is crucial for the nuclear accumulation of CPC:GFP. To evaluate the tissue-specificity of CPC movement, CPC:GFP was expressed in the stele using the SHR promoter and in trichoblasts using the EGL3 promoter. CPC:GFP was able to move from trichoblasts to atrichoblasts but could not exit from the stele, suggesting the involvement of tissue-specific regulatory factors in the intercellular movement of CPC. Analyses with a secretion inhibitor, Brefeldin A, and with an rhd3 mutant defective in the secretion process in root epidermis suggested that intercellular CPC movement is mediated through plasmodesmata. Furthermore, the fusion of CPC to tandem-GFPs defined the capability of CPC to increase the size exclusion limit of plasmodesmata.
Kurata
Tetsuya
T
Plant Science Center, RIKEN, 1-7-22 Suehiro-cho, Tsurumi-ku, Kanagawa 230-0045, Japan.
Ishida
Tetsuya
T
Kawabata-Awai
Chie
C
Noguchi
Masahiro
M
Hattori
Sayoko
S
Sano
Ryosuke
R
Nagasaka
Ryoko
R
Tominaga
Rumi
R
Koshino-Kimura
Yoshihiro
Y
Kato
Tomohiko
T
Sato
Shusei
S
Tabata
Satoshi
S
Okada
Kiyotaka
K
Wada
Takuji
T
D019943:Amino Acid Substitution; D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D020126:Brefeldin A / Q000494:pharmacology; D002454:Cell Differentiation; D002467:Cell Nucleus / Q000502:physiology; D019204:GTP-Binding Proteins / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D049452:Green Fluorescent Proteins / Q000235:genetics; D009154:Mutation; D019441:Plant Epidermis / Q000166:cytology / Q000502:physiology*; D018517:Plant Roots / Q000502:physiology*; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D021381:Protein Transport; D020598:Proto-Oncogene Proteins c-myb / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
D029681:Arabidopsis Proteins; C511989:CPC protein, Arabidopsis; D011500:Protein Synthesis Inhibitors; D020598:Proto-Oncogene Proteins c-myb; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D020126:Brefeldin A; D019204:GTP-Binding Proteins; C464507:RHD3 protein, Arabidopsis