Premium
The Ca 2+ ‐binding protein PC aP2 located on the plasma membrane is involved in root hair development as a possible signal transducer
Author(s) -
Kato Mariko,
Aoyama Takashi,
Maeshima Masayoshi
Publication year - 2013
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12155
Subject(s) - root hair , calmodulin , microbiology and biotechnology , wild type , chemistry , mutant , biology , biochemistry , biophysics , gene , enzyme
Summary Plasma membrane‐associated Ca 2+ ‐binding protein–2 ( PC aP2) of A rabidopsis thaliana is a novel‐type protein that binds to the Ca 2+ /calmodulin complex and phosphatidylinositol phosphates (PtdInsPs) as well as free Ca 2+ . Although the PC aP2 gene is predominantly expressed in root hair cells, it remains unknown how PC aP2 functions in root hair cells via binding to ligands. From biochemical analyses using purified PC aP2 and its variants, we found that the N–terminal basic domain with 23 amino acids (N23) is necessary and sufficient for binding to PtdInsPs and the Ca 2+ /calmodulin complex, and that the residual domain of PC aP2 binds to free Ca 2+ . In mutant analysis, a pcap2 knockdown line displayed longer root hairs than the wild‐type. To examine the function of each domain in root hair cells, we over‐expressed PC aP2 and its variants using the root hair cell‐specific EXPANSIN A7 promoter. Transgenic lines over‐expressing PC aP2, PC aP2 G2A (second glycine substituted by alanine) and ∆23 PC aP2 (lacking the N23 domain) exhibited abnormal branched and bulbous root hair cells, while over‐expression of the N23 domain suppressed root hair emergence and elongation. The N23 domain was necessary and sufficient for the plasma membrane localization of GFP ‐tagged PC aP2. These results suggest that the N23 domain of PC aP2 negatively regulates root hair tip growth via processing Ca 2+ and PtdInsP signals on the plasma membrane, while the residual domain is involved in the polarization of cell expansion.