A novel pollen-specific alpha-tubulin in sunflower: structure and characterization.
We describe here a new alpha-tubulin isoform from sunflower we named alpha(pi)-tubulin. Alpha(pi)-tubulin is the most divergent higher-plant alpha-tubulin described so far, having an unusual deletion in the H1/B2 loop and a glutamine-rich C-terminus. We constructed a three-dimensional model and discuss its implications. Using specific antibodies, we show that alpha(pi)-tubulin expression is restricted to the male gametophyte. Alpha(pi)-tubulin mRNA represents 90% of alpha-tubulin mRNA and a small percentage of total pollen mRNA. Among the plants tested, alpha(pi)-tubulin was only detected in sunflower and in Cosmos. Since both plants are Asteraceae, we propose that alpha(pi)-tubulin is specific to this family. Our results suggest that alpha(pi)-tubulin can inhibit tubulin assembly in pollen. This hypothesis is reinforced by the fact that alpha(pi)-tubulin is found in a complex with beta-tubulin in mature sunflower pollen.
Evrard
Jean-Luc
JL
Institut de Biologie Moléculaire des Plantes du CNRS, Strasbourg, France. jean-lux.evrard@ibmp-ulp.u-strasbg.fr
Nguyen
Isabelle
I
Bergdoll
Marc
M
Mutterer
Jérĵme
J
Steinmetz
André
A
Lambert
Anne-Marie
AM
D000595:Amino Acid Sequence; D019659:Asteraceae / Q000235:genetics; D001483:Base Sequence; D015153:Blotting, Western; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D015870:Gene Expression; D006368:Helianthus / Q000235:genetics*; D007150:Immunohistochemistry; D008870:Microtubules / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011058:Pollen / Q000235:genetics* / Q000254:growth & development; D011487:Protein Conformation; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014026:Nicotiana / Q000235:genetics; D014404:Tubulin / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
D018076:DNA, Complementary; D020033:Protein Isoforms; D014404:Tubulin