Poster: Organelle Biogenesis

Abs # 1133: Large-scale genetic analysis of albino and pale green (apg) mutants using Ac/Ds transposon system in Arabidopsis.

Presenter:	Myouga, Fumiyoshi , fmyouga@gsc.riken.go.jp
Authors	Myouga, Fumiyoshi  (A) (B)  Motohashi, Reiko  (A)   Yamazaki, Takanori  (C) (D)  Ito, Takuya  (C)   Kuromori, Takashi  (A)   Hirayama, Takashi  (A)   Seki, Motoaki  (A) (C)  Kobayashi, Masatomo  (E)   Nagata, Noriko  (F)   Yoshida, Shigeo  (F)   Shinozaki, Kazuo  (A) (C)
Affiliations:	(A): RIKEN, Genome Science Center (B): GENESIS Res. Inst., Inc. (C): RIKEN, Plant Molecular Biology (D): Tsukuba Univ.,Biol. Sci. (E): RIKEN, BioResouce Center (F): RIKEN, Plant Science Center

To identify large numbers of Arabidopsis genes responsible for chloroplast development and pigment synthesis, we collected transposon-tagged albino and pale green mutants. We transposed Dissociation (Ds) elements from 3 start loci on chromosome 5 and 4 loci on chromosome 1 in Arabidopsis thaliana and made more than ten thousand Ds-tagged lines of F3 plants carrying independent transposition events. From screening 9,425 Ds-tagged lines, we identified 87 albino or pale green (apg) mutants, completed cosegregation analysis of the insertion for 39 mutants. Thus, our Ds-tagging population (about 45 %) is more efficient for gene isolation than T-DNA tagging populations. Nineteen of the apg mutants are albino, 15 pale green, 3 white cotyledon and 2 variegated. We further analyzed their Ds-tagged genes of apg mutants to predict functions of the encoded proteins. Most of the apg mutations seem to affect chloroplast functions because Ds-tagged genes encode proteins with transit peptides that function chloroplast localization. In 36 apg mutants, 21 mutants have Ds insertions in genes with known functions on the basis of BLAST searches. Genes of 15 Ds-tagged mutants encode proteins with unknown functions. In this study, we analyzed six nuclear genes (APG1-6) of which mutants showed a characteristic albino and pale green phenotype. We discuss functions of six gene products; (1) a protein involved in methylation of plastoquinone (APG1), (2) a tatC homologue involved in chloroplast protein translocation to thylakoid membrane (APG2), (3) a translation release factor homologue (APG3), (4) a ribosome binding factor homologue (APG4), (5) a PSII component with variegation phenotype (APG5), (6) heat shock protein (APG6). Our recent analysis of apg6 mutants will be precisely presented.