ROOT HAIR DEFECTIVE3 family of dynamin-like GTPases mediates homotypic endoplasmic reticulum fusion and is essential for Arabidopsis development.
In all eukaryotic cells, the endoplasmic reticulum (ER) forms a tubular network whose generation requires the fusion of ER membranes. In Arabidopsis (Arabidopsis thaliana), the membrane-bound GTPase ROOT HAIR DEFECTIVE3 (RHD3) is a potential candidate to mediate ER fusion. In addition, Arabidopsis has two tissue-specific isoforms of RHD3, namely RHD3-like (RL) proteins, and their function is not clear. Here, we show that a null allele of RHD3, rhd3-8, causes growth defects and shortened root hairs. A point mutant, rhd3-1, exhibits a more severe growth phenotype than the null mutant, likely because it exerts a dominant-negative effect on the RL proteins. Genetic analysis reveals that the double deletion of RHD3 and RL1 is lethal and that the rhd3 rl2 plants produce no viable pollen, suggesting that the RL proteins are redundant to RHD3. RHD3 family proteins can replace Sey1p, the homolog of RHD3 in yeast (Saccharomyces cerevisiae), in the maintenance of ER morphology, and they are able to fuse membranes both in vivo and in vitro. Our results suggest that RHD3 proteins mediate ER fusion and are essential for plant development and that the formation of the tubular ER network is of general physiological significance.
Department of Genetics and Cell Biology , College of Life Sciences, Nankai University, and Tianjin Key Laboratory of Protein Sciences, Tianjin 300071, China.
Miao
M
Zhang
Fuyun
F
Wu
Juanming
J
Shi
Yimeng
Y
Zhu
Zhengmao
Z
Zhu
Qingqiu
Q
Gong
Junjie
J
Hu
D017360:Arabidopsis / Q000201:enzymology* / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D034281:Dynamins / Q000378:metabolism*; D004721:Endoplasmic Reticulum; D019204:GTP-Binding Proteins / Q000378:metabolism*; D017353:Gene Deletion; D008561:Membrane Fusion; D063245:Plant Development; D012441:Saccharomyces cerevisiae / Q000378:metabolism
D029681:Arabidopsis Proteins; D019204:GTP-Binding Proteins; C464507:RHD3 protein, Arabidopsis; D034281:Dynamins