M. Heddad et I. Adamska, Light stress-regulated two-helix proteins in Arabidopsis thaliana related to the chlorophyll a/b-binding gene family, P NAS US, 97(7), 2000, pp. 3741-3746
Citations number
43
Categorie Soggetti
Multidisciplinary
Journal title
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
The chlorophyll a/b, chlorophyll a/c, and chlorophyll a/a light-harvesting
proteins are part of an extended gene family that also includes the transie
ntly expressed stress proteins, the flips (early light-induced proteins). F
our flip homologue proteins, encoded by single-copy nuclear genes, have bee
n identified in the Arabidopsis thaliana database. These proteins were divi
ded into two groups according to the expression pattern under light-stress
conditions and the predicted secondary structure. Group one included two me
mbers of the Flip family with three predicted transmembrane helices and a g
ene expression strictly related to light stress. Group two included two pro
teins, the Seps (stress-enhanced proteins), which possessed two predicted t
ransmembrane segments. The transcripts of Sep1 and Sep2 were present under
low light conditions, but their level increased 4- to 10-fold during illumi
nation of plants with high-intensity light. Preliminary data indicated that
the induced transcripts were translated in vivo. Other physiological stres
s conditions, such as cold, heat, desiccation, salt wounding, or oxidative
stress, did not significantly influence the expression of Sep genes. In vit
ro import of radioactively labeled precursors of Seps into isolated chlorop
lasts confirmed the thylakoid membrane localization of these proteins. Cons
idering the predicted protein structure and homology to other pigment-anten
na proteins, the two-helix Seps might represent an evolutionary missing lin
k between the one- and three-helix antenna proteins present in pro- and euk
aryota.